HSEHealth & Safety

Executive

The effects of thermal environments on the risks associated with manual handling

Prepared by The Health and Safety Laboratoryfor the Health and Safety Executive 2005

RESEARCH REPORT 337

HSEHealth & Safety

Executive

The effects of thermal environments on therisks associated with manual handling

S. Powell PhD, BSc (Hons) A. Davies BSc (Hons) MSc

J. Bunn BSc, MSc D. Bethea BSc (Hons)

The Health and Safety LaboratoryHarpur Hill

BuxtonDerbyshire

SK17 9JN

Manual handling injuries are a major occupational health problem. The risk factors associated withmanual handling in hot and cold environments were identified as a gap in knowledge under the Healthand Safety Executive’s priority programme for musculoskeletal disorders (MDS’s). At present themanual handling guidance does not offer specific guidance regarding manual handling in non-neutralthermal environments other than to say that extremes of temperature and humidity should be avoided.Two experiments were designed to assess the effects on nonneutral thermal environments on manualhandling. The thermal environments for this study are defined as manual handling events that occurwithin sub-ranges of a 0°C to 40°C range. For the purpose of this study a cold environment is definedas between 0°C – 10°C (44% – 60% relative humidity) and a hot environment is defined as between29°C – 39°C (25% - 72% relative humidity). The results and implications of this experimental work arediscussed in this report.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Itscontents, including any opinions and/or conclusions expressed, are those of the authors alone and donot necessarily reflect HSE policy.

HSE BOOKS

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© Crown copyright 2005

First published 2005

ISBN 0 7176 2995 3

All rights reserved. No part of this publication may bereproduced, stored in a retrieval system, or transmitted inany form or by any means (electronic, mechanical,photocopying, recording or otherwise) without the priorwritten permission of the copyright owner.

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ACKNOWLEDGEMENTS

Andrew Davies from The School of Exercise Science at Sheffield Hallam University conducted the experimental work for this project and provided a preliminary report on the findings as part of his PhD. Dr. John Saxton and Dr. Alison Purvis also from the School of Exercise Science at Sheffield Hallam University should be acknowledged in this report as Andrew Davies’ PhD supervisors. Dr. Mark Boocock was the original project leader for this work and should be acknowledged as such. Dr. Andrew Pinder (HSL) assisted in the statistical analysis of the results. iii

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CONTENTS

CONTENTS...................................................................................................................V

1 INTRODUCTION................................................................................................... 1

1.1 BACKGROUND .................................................................................................... 1

1.2 ADVICE ON THERMAL EXTREMES WITHIN MANUAL HANDLING GUIDANCE..................................................................................................................... 1

1.3 ACCIDENT AND INJURY DATA.......................................................................... 3

1.4 HUMAN THERMOREGULATORY RESPONSES................................................ 4

1.5 HEAT STRESS AND IMPLICATIONS FOR MANUAL HANDLING..................... 6

1.6 COLD AND IMPLICATIONS FOR MANUAL HANDLING.................................... 9

1.7 HYPOTHESES – HOT STUDY ........................................................................... 11

1.8 HYPOTHESES – COLD STUDY......................................................................... 12

2 METHODS .......................................................................................................... 13

2.1 THE PHYSIOLOGICAL APPROACH OF ASSESSING MANUAL HANDLING TASKS.......................................................................................................................... 13

2.2 THE PSYCHOPHYSICAL APPROACH TO ASSESSING MANUAL HANDLING TASKS.......................................................................................................................... 13

2.3 SITE VISITS ........................................................................................................ 15

3 EXPERIMENT 1: ‘HOT’ EXPERIMENT.............................................................. 16

3.1 DESIGN............................................................................................................... 16

3.2 PROCEDURE ..................................................................................................... 16

3.3 ACCLIMATISATION ........................................................................................... 17

3.4 LIFTING TASK.................................................................................................... 17

3.5 EXPERIMENTAL SESSIONS............................................................................. 18

3.6 PARTICIPANTS.................................................................................................. 19

3.7 ENVIRONMENTAL MEASuREMENT ................................................................ 19

3.8 WITHDRAWAL CRITERIA ................................................................................. 20

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3.9 ANALYSIS .......................................................................................................... 20

4 RESULTS............................................................................................................ 21

4.1 ASSUMPTIONS .................................................................................................. 21

4.2 HEART RATE ..................................................................................................... 21

4.3 CORE TEMPERATURE...................................................................................... 23

4.4 RATE OF PERCEIVED EXERTION.................................................................... 25

4.5 MAXIMUM ACCEPTABLE WEIGHT OF LIFT (MAWL)..................................... 27

5 DISCUSSION – HOT EXPERIMENT .................................................................. 30

5.1 HYPOTHESES.................................................................................................... 35

6 EXPERIMENT 2: ‘COLD’ EXPERIMENT ........................................................... 36

6.1 DESIGN............................................................................................................... 36

6.2 PROCEDURES ................................................................................................... 36

6.3 ORIENTATION PERIOD..................................................................................... 37

6.4 LIFTING TASK.................................................................................................... 37

6.5 EXPERIMENTAL SESSIONS............................................................................. 38

6.6 PARTICIPANTS.................................................................................................. 38

6.7 ENVIRONMENTAL MEASUREMENT................................................................ 39

6.8 WITHDRAWAL CRITERIA ................................................................................. 39

6.9 ANALYSIS .......................................................................................................... 39

7 RESULTS............................................................................................................ 40

7.1 ASSUMPTIONS .................................................................................................. 40

7.2 HEART RATE ..................................................................................................... 40

7.3 CORE TEMPERATURE...................................................................................... 41

7.4 RATE OF PERCEIVED EXERTION.................................................................... 44

7.5 MAXIMUM ACCEPTABLE WEIGHT OF LIFT ................................................... 45

8 DISCUSSION – COLD EXPERIMENT................................................................ 48

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8.1 HYPOTHESES.................................................................................................... 51

9 CONCLUSIONS AND RECOMMENDATIONS FOR RISK ASSESSMENT....... 52

10 FURTHER WORK............................................................................................... 55

11 REFERENCES.................................................................................................... 57

12 GLOSSARY ........................................................................................................ 63

APPENDIX 1 SUMMARY OF CURRENT THERMAL STANDARDS .......................... 64

APPENDIX 2 MANUAL HANDLING IN THERMAL ENVIRONMENTS: SITE VISIT SUMMARIES................................................................................................................ 66

APPENDIX 3 PARTICIPANT INFORMATION........................................................... 102

APPENDIX 4 PRE-SCREENING QUESTIONNAIRE ................................................ 103

APPENDIX 5 PSYCHOPHYSICS SCRIPT ................................................................ 105

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EXECUTIVE SUMMARY

OBJECTIVES

Manual handling injuries are a major occupational health problem. The risk factors associated with manual handling in hot and cold environments were identified as a gap in knowledge under the Health and Safety Executive’s priority programme for musculoskeletal disorders (MDS’s). The findings from this research may be used to produce practical guidance on manual handling in non-neutral thermal environments. At present the guidance does not offer specific guidance regarding manual handling in non-neutral thermal environments other than to say that extremes of temperature and humidity should be avoided. The thermal environments for this study are defined as manual handling events that occur within sub-ranges of a 0°C to 40°C range. For the purpose of this study a cold environment is defined as between 0°C – 10°C (44% – 60% relative humidity) and a hot environment is defined as between 29°C – 39°C (25% - 72% relative humidity). Aims for this project were: To conduct a literature review on manual handling in hot and cold environments To investigate some of the thermal environments in UK industry where manual handling is conducted To examine through experimental work psychophysical and physiological responses to manual handling in non-neutral thermal environments To determine manual handling risk factors in thermal working environments (hot and cold) Methodology: Site visits within UK industry were conducted to ensure the validity of the experimental conditions selected. Manual handling activities and the thermal environments were characterised and quantified at each location. Notes of clothing/PPE worn and overall activity levels were also taken.12 male participants took part in two studies. Participant’s core temperature, skin temperature, heart rate and rating of perceived exertion (RPE) were taken. Participants were asked to lift a box at a set frequency from the floor to knuckle height at a set frequency. There were three different frequencies of lift. Participants were able to adjust the weight of the load lifted to a level that they felt that they would be able to sustain for an eight-hour shift. This is defined as the maximum acceptable weight of lift (MAWL).

MAIN FINDINGS The main findings were: Little information is available on manual handling in non-neutral thermal environments Non-neutral thermal environments affect manual handling There is significant variation between individuals in terms of their physiological responses to manual handling in non-neutral thermal environments Workers are unable to effectively assess their level of physiological strain when manual handling in non-neutral thermal environments

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Frequency of lift has a significant effect on physiological responses to manual handling in non-neutral thermal environments.

• Humidity has a significant effect on physiological strain when manual handling in hot thermal environments so air temperature alone is not a good indicator of physiological strain

• The use of Psychophysical testing may be inappropriate for assessing manual handling risks in non-neutral thermal environments

CONCLUSIONS AND RECOMMENDATIONS

• Where manual handling in hot environments is unavoidable work regimes should allow for regular access to drinking water

• The level of activity should be considered in any risk assessments on manual handling in non-neutral thermal environments

• Any risk assessment for assessing additional physiological strain of manual handling in a hot environment could be simply based on heart rate.

• The current L23 risk filter is not adequate in identifying the increased risks associated with manual handling in hot environments. Completion of a more detailed risk assessment i.e. the environment as well as the manual handling task or tasks is advised in hot environments may be required. Suggestions for possible risk factors (e.g. individual variation, misperception of physiological strain) for inclusion in L23 and additional guidance are given in this report for manual handling in hot thermal environments.

• Workers may select weights and/or lifting frequencies that are excessive as a strategy for keeping warm in cold environments, however this risk should be filtered out by the L23 risk filter.

• Additional advice is suggested for inclusion in the guidance regarding appropriate clothing levels for manual handling in cold environments.

• For manual handling in cold environment s at higher lifting frequencies (i.e. 1 lift every 14 seconds and above) where there are no long periods of inactivity and appropriate clothing is worn) the risk filter in L23 should suffice.

• At low lifting frequencies (where there are long periods of inactivity) additional risk factors are present in cold environments that are not currently considered by the L23 risk filter and a more detailed risk assessment is advised. Additional guidance and risk factors are suggested (e.g. inappropriate selection of PPE).

In summary, the risk filter in L23 is probably sufficient to screen additional risk of manual handling in cold environments (above 0°C) at lifting frequencies were there are no prolonged periods of inactivity and where appropriate clothing is worn. In all other non-neutral thermal environments where manual handling is undertaken it is advised that an additional risk assessment is conducted.

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1 INTRODUCTION

1.1 BACKGROUND

Manual handling activities can be defined as ‘the transporting or supporting of a load. This includes lifting, lowering, pushing, pulling, carrying or moving. The load may either be for example, a box or trolley, or a person or animal’ (Health & Safety Executive [HSE], 2004). Manual handling activities are common across a wide range of work environments and have been identified as a major contributor to reported workplace injuries. Whilst fatalities resulting from manual handling accidents are rare, manual handling accidents often result in serious injury and account for 38% of all RIDDOR (reporting on injuries, diseases and dangerous occurrences regulations) reportable accidents (requiring three or more days absence from the workplace in the UK) (HSE, 2004). Injuries to the lower-back accounted for 47% of all reported handling accidents requiring three or more days absence from work in 2001/02; the finger and the upper-limbs were also identified as areas at increased risk of injury. These injuries may have been the result of an acute event or cumulative exposure to manual handling over time (Dickinson, 1995). In 1992 (updated in 2004) HSE published its guidance (L23) on the Manual Handling Operations Regulations. This implemented European Directive 90/269/EEC on manual handling of loads, and was designed to help employers and employees reduce the risk of injury from manual handling tasks across all industries. The thermal environment and ventilation are two aspects of the work environment that are recognised as factors that can increase the risk of injury from manual handling operations. However, there is currently no specific guidance on how important these risk factors are, or on how to identify and control these risks. 1.2 ADVICE ON THERMAL EXTREMES WITHIN MANUAL HANDLING

GUIDANCE

1.2.1 UK manual handling guidance

L23 recommends that, where manual handling operations cannot be avoided, a risk assessment should be conducted taking into consideration specific risk factors of the task, load, physical and organisational work environment, and individual capability. These risk factors are interrelated and cannot be considered in isolation (HSE, 2004). L23 states that "high temperatures or humidity can cause rapid fatigue" and that "work at low temperatures may impair dexterity" (HSE, 2004). It also goes on to say that that "there is less risk of injury if manual handling is performed in a comfortable working environment" and that "extremes of temperature, excessive humidity and poor ventilation should be avoided where possible". However, the magnitude of the risks and range of environmental temperatures and humidity outside of which the injury risks increase are not quantified. HSE (2003) has also developed manual handling assessment charts (MAC), as a tool for inspectors, employers, safety representatives and others to prioritise manual handling risk factors. “Extremes of temperature” are mentioned as one environmental risk factor; however, no other information is provided. 1.2.2 International and European standards

In addition to UK guidance on manual handling, European and International standards that address manual handling practices are also available. For example, in BS EN 1005 – 2:2003 ‘Manual Handling of Machinery and Component Parts of Machines’, environmental factors are

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not described in detail. It is noted that care should be taken where work has to be conducted at extremes of temperature. In particular, high temperature and humidity are identified as possible causes of rapid fatigue, while work at low temperatures "may cause numbness or require gloves with loss of manual dexterity". Additionally, the reader is directed to existing standards for further guidance. Annex B recommends attention to thermal comfort requirements specified in ISO 7730:1995 ‘Moderate thermal environments. Determination of the PMV and PPD indices and specification of the conditions for thermal comfort’. The limits of thermal comfort during manual handling, quoted directly from ISO 7730 (1995), are 19˚C – 26˚C, 30 – 70% relative humidity and an air velocity ≤ 0.2 m.s-1. ISO 11228-1: 2003 ‘Ergonomics – Manual Handling Part 1: Lifting and Carrying’ also contains ergonomic recommendations for different manual handling tasks. Again, when thermal environments are considered, there are no specific recommendations although increased airflow is recommended at high air temperatures and it points out that extra care should be taken at extremes of temperature. The reader is then directed to ISO 7730 (1995) for guidance. Likewise, there are no thermal environment standards that deal specifically with the effect on manual handling of different thermal environments. Current thermal standards are summarised in Appendix 1. Any mention of manual handling activities in non-neutral thermal environments generally states that extremes of temperature should be avoided, as should extremes of humidity. At best, users are referred to ISO 7730 (1995) for guidance. 1.2.3 Other guidance

The National Institute for Occupational Safety and Health (NIOSH) developed a revised lifting equation to determine protective weight limits for the working population (Waters et al., 1993). Amongst the limitations identified was the inability to account for a working environment outside the temperature range of 19 – 26˚C or a relative humidity range exceeding 35 – 50%. Using data from Hafez (1984), Hidalgo et al. (1997) subsequently proposed a comprehensive lifting model that built on the revised NIOSH equation and incorporated, an environmental variable – wet bulb globe temperature variable (WBGT). As described in BS EN 27243 (1994), a WBGT value is derived from a number of environmental parameters to indicate heat stress. However, a WBGT value can be achieved from a number of very different environments. For example, a given WBGT value of 32°C could relate to a hot dry environment (e.g. Ta = 40°C and 30% relative humidity) or a ‘warm’ wet environment (e.g. Air temperature (Ta) = 31°C and 80% relative humidity). In using WBGT, Hidalgo et al. (1997) assumes that similar WBGT values will impose the same thermal load on a person regardless of the actual environment. This assumption is now challenged, as it is believed that in more humid environments heat stress is greater due to the decreased potential for the evaporation of sweat (Kellett et al., 2003; Havenith et al., 1998). A number of other studies have also shown that similar WBGT values used to describe different environments can have a different physiological effect (Keatisuwan et al., 1996; Greifahn 1996). This has important consequences for work in industry, as although limit values can be set based on WBGT values, they do not necessarily accurately describe the level of physiological strain a person may be experiencing. However, Griefahn (1997) demonstrated that irrespective of different thermal environments at equivalent WBGT values, the course of acclimatisation is similar. It was also shown that acclimatisation to a defined hot environment conferred equal acclimation to any other equivalent climate. Hidalgo et al. (1997) did not address the different physiological stressors that may be imposed at differing thermal environments (e.g. hot dry versus warm humid environments) but similar WBGT values nor other factors responsible for thermal comfort such as clothing.

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1.3 ACCIDENT AND INJURY DATA

The HSE carry out workplace inspections at all sites where a fatal injury has occurred and at a percentage of sites where a non-fatal injury has occurred. These visits are recorded in the HSE's FOCUS database and may include inspectors' comments regarding the characteristics of the workplace e.g. environment. The FOCUS database therefore provides a potential means of identifying working environments where a thermal component may have been a contributory factor in the causation of an injury. A recent search identified meat and poultry processors, fruit and vegetable stores, hospitals, brewers, bakeries, textiles, plastics and paper manufacturers as sites where manual handling tasks and uncomfortable thermal environments might interact to increase the risk of injury. Most of the descriptions of environmental conditions were generalised with less than ten providing air temperature measurements. These limitations make quantification of the scale of manual handling risks using FOCUS in thermal environments extremely difficult. Data regarding work related ill health in UK workplaces are collected from a variety of sources. This includes information on musculoskeletal disorders. Information on work related ill health is included in the Labour Force Survey (LFS), a survey of approximately 60,000 households. Information is also collected under the voluntary reporting of occupational diseases via the Health Occupation Reporting Network (THOR) previously known as the Occupational Disease Intelligence Network (ODIN). The data for MSD’s is derived from two schemes the Occupational Physicians Reporting Activity (OPRA) or the Musculoskeletal Occupational Surveillance Scheme (MOSS). A 1995 survey of self reported work related illness SWI95 is also available and a more recent SWI survey conducted in 2001/02 is now also available. These sources of information ‘provide an indication of the overall prevalence of work-related illness and its distribution by major disease group and a range of demographic and employment related variables’ (http://www.hse.gov.uk/statistics/causdis/sources.htm). Additionally, any injury or ill health resulting in an absence from work of more than three days is reportable to the Health & Safety Executive (HSE) or local authority. This reporting is mandatory under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1985 and 1995 (RIDDOR). The LFS and RIDDOR data are complementary and are used to monitor workplace safety and direct resources within the HSE. When comparing the data collected by RIDDOR with data from the LFS it can be seen that reporting levels for workplace injuries are generally lower for RIDDOR than those encountered in the LFS and vary widely depending on industry. In the transport, storage and communication industries for instance, the reporting rate was around 75% when comparing injury data from the LFS and RIDDOR (HSE, 2001). In the manufacturing and construction sectors, these figures were 57% and 52% respectively. In the hotels and restaurants industries however this figure dropped to just 19% (i.e. LFS reported 1,400 injuries per 100,000 workers yet via RIDDOR the figure was only 267 per 100,000 workers) (HSE, 2001). The LFS does not classify injury types however, so it is necessary to consult RIDDOR to obtain this information. What is unclear is the extent to which non-neutral thermal environmental conditions, particularly extremes of temperature and/or humidity, contribute to manual handling injuries. Thermal environment information where reported is of limited use as it is usually in the form of air temperature only. The Bureau of Labour Statistic of the United States (2002) showed the highest incidence rates of disorders in 2000 occurring in meat packing plants, poultry slaughtering processes and sausage and other prepared meat processing plants. These specific industries came first, third and sixth out of all private sector industries. Workers in these factories are continually exposed to low air temperatures during their working day.

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1.4 HUMAN THERMOREGULATORY RESPONSES

Human beings are 'homeotherms', that is they attempt to maintain a constant body temperature despite changes in the surrounding environment (Powers & Howley, 1997). Core temperature is maintained at an average of 37˚C (Parsons, 1993), varying within a narrow range of ~35.6-37.8˚C (Marieb, 1998). Temperature regulation is controlled by the thermoregulatory centres in the hypothalamus. The hypothalamus receives afferent input from both peripheral and central thermoreceptors (Marieb, 1998). Peripheral thermoreceptors monitor the temperature of the skin whilst central thermoreceptors (some of which are located in the hypothalamus) are sensitive to changes in the temperature of the blood (Marieb, 1998). Regulatory and feedback mechanisms attempt to control any deviations from normal temperature. These mechanisms are discussed briefly below. 1.4.1 Control of heat loss

An increase in core temperature above 40 - 41˚C can cause dysfunction of the central nervous system and there is a risk of death above 43 - 44˚C (Powers & Howley, 1997). Heat loss is achieved by four methods: radiation, conduction, convection and evaporation. The second law of thermodynamics states that heat will always flow from a warm object to a cool object, so heat will always pass from the human to the environment providing the environment is cooler than the human. The temperature difference between the body and the environment is known as the thermal gradient. Where a thermal gradient exists in the opposite direction, a cold body will absorb heat from a warm environment. In the event of a rise in core temperature, the hypothalamus activates heat-loss mechanisms. Vasodilation of the cutaneous blood vessels will occur as a result of an inhibition of vasomotor tone (Marieb, 1998). The increased blood flow to the skin's surface facilitates increased heat transfer from the body to the environment by radiation, conduction and convection (assuming the environment is cooler than the body). Sweat glands are activated and the individual begins to sweat, this aids evaporative cooling and is the predominant mechanism for heat loss in a human but this mechanism is severely compromised in very humid conditions. In environments with high humidity levels the moisture gradient between the body and surrounding air will be shallow and evaporation may be negligible. This danger is recognised by many of the world's sports governing bodies who issue guidelines on whether events should take place or not depending on the prevalent conditions. The American College of Sports Medicine have for instance published a position statement on the prevention of thermal injuries during distance running (ACSM, 1985). 1.4.2 Control of heat promotion

Cold stress is a major risk to the health of an individual and the human body attempts to counteract this by thermogenesis. Thermogenesis takes two forms, shivering and non-shivering. Vasoconstriction of the cutaneous blood vessels occurs first in order to restrict the flow of blood to the skin's surface thus reducing heat loss to the environment and circulating more blood closer to the body’s organs. Noradrenalin (NA) is released, increasing the metabolic rate and also heat production (Marieb, 1997). This is known as non-shivering thermogenesis. If this is not sufficient to maintain core temperature then the body will invoke a shivering response. This initially takes the form of asynchronous firing of muscle fibres but then graduates onto synchronised firing of the muscle fibres of the neck (Parsons 1993). Other muscle groups are then recruited, the neck being first so that brain temperature can be maintained. Should the core temperature fall below 35˚C then the individual is considered to be suffering from hypothermia (Holmer, 1994b). At this temperature the muscles stiffen, the viscosity of the

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blood increases and there is a reduction in cognitive capability e.g. confusion and apathy leading to a loss of sensory information (Parsons, 1993). At 30 - 31˚C the individual lapses into unconsciousness and any further fall in core temperature will probably result in death due to ventricular fibrillation (Parsons, 1993). Parsons (1993) identified considerable inter-individual variation in the ability to withstand extremely low core temperatures, citing a case where complete recovery was achieved in an accidental hypothermia victim with a core temperature of 18˚C. Indeed, the lowest core temperature recorded in a recovered person was measured at 9˚C during a controlled experiment where the subject was deliberately cooled (Parsons, 1993). 1.4.3 Inter-individual variations

It is acknowledged in all Standards documents relating to human responses to the environment that there may be considerable inter-individual variability in responses to heat stress. Therefore factors such as gender, acclimatisation, fitness and medical history for example may have a profound effect on the ability to conduct manual handling tasks in any environment. The Standards do not predict the responses of individuals but provide guidance for "standard subjects in good health and fit for the work they perform" (ISO 7933, 1989). Individual responses to hot and cold environments whilst at rest and during exercise can be modified by factors such as age, acclimatisation state, gender, body composition, fitness levels and working shift patterns. The interaction of these factors however is not clearly determined. It is unclear, for example, how significant age is in itself or whether the responses of older people are affected by associated factors such as increases in body fat percentage and a decline in physical fitness. As a result of decreased physical fitness, any exertion places more demand on the cardio vascular system than it would on a fitter person. This leaves less cardiovascular reserve to cope with thermoregulation and directly affects the body’s ability to cool by means of vasodilation. The reduction in activity can also affect a person’s acclimatisation (Havenith 1985). Shephard (1996) has argued that many of the deleterious effects of ageing are not inevitable but more likely to be caused by an overall reduction in activity levels. Wagner et al. (1974) monitored the rectal and mean skin temperature of four groups of males (10-13 y, 14-16 y, 20-29 y and 46-67 y) as they rested in a thermal neutral environment (30˚C dry bulb, 15˚C wet bulb) for one hour and then for a further 30 minutes in a cold environment (16 - 17˚C dry bulb, 10˚C wet bulb). The participants (n = 33) were dressed in shorts and socks and reclined on a bed in the controlled environment. During rest in the cold, the mean rectal temperature (Trec) decreased and mean skin temperature (Tsk) increased for all groups. Trec and Tsk were highest in the youngest group and lower as the age of the groups increased. It was noted that the lower temperatures with age were accompanied by lower metabolic rates (measured by expired gas analysis) and reduced cutaneous blood flow. When the ambient temperature was decreased, all groups initially demonstrated a continued decrease in Trec. After approximately six minutes, Trec in the youngest group started to rise and there was a similar, if blunted, response in the next youngest group. In the 19-29 y group, Trec was maintained at an almost constant level but in the oldest group it continued to decline throughout the experiment. Tsk declined throughout the cold exposure for all participants but the younger groups maintained a higher skin temperature at the chest and back. Measurements of finger blood flow were lowest for the youngest group and increased with age, suggesting that the younger subjects invoked a more pronounced vasoconstrictive response. This study concluded that age significantly affected thermoregulatory responses. However, it did not take into account differences in body composition or fitness levels. The majority of the studies that have examined the effects of physical fitness on thermoregulatory responses have utilised maximal oxygen uptake (VO2max) as the fitness marker (Bittel et al., 1988; Havenith et al., 1995). Bittel et al. (1988) reported that individuals

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with a higher VO2max had more efficient thermoregulatory responses to cold stress as measured by mean skin temperature, metabolic heat production, skin conductance and mean skin temperature at onset of shivering. As VO2max was highly negatively correlated to body fat percentage (r = -0.77, p<0.01), the contribution of each variable was unclear. 1.5 HEAT STRESS AND IMPLICATIONS FOR MANUAL HANDLING

Studies investigating manual handling in non-neutral thermal environments are sparse and differences in manual handling tasks, protocols and environment make it difficult for industry and regulators to draw meaningful conclusions. Hence, there is a lack of prescriptive advice in the guidance and regulations (see Section 2). The majority of research indicates that manual handling in non-neutral thermal environments may increase the risk of physiological strain, but to what extent, under what conditions and what manual handling tasks are affected is not known. Some risk factors are easily identifiable; for example, increased sweat secretion that may result in a decreased grip on an object. However, the more insidious underlying effects of manual handling in the heat require further research. An Increased risk of musculoskeletal injury associated with work in hot environments. Harkness et al (2003), for example identified work in a hot environment as a risk factor for new-onset low back pain amongst cohorts of newly employed workers. An early study conducted by Kamon & Belding (1971) assessed the physiological cost of carrying loads in temperate and hot environments. Participants were asked to carry cartons weighing 10, 15 and 20 kg whilst walking on a treadmill at two different speeds and gradients. Each session consisted of three five-minute exercise sessions separated by five-minute rest periods. The ambient temperature in which the tasks were carried out in ranged from 20 - 45˚C dry bulb. Wet bulb temperatures were reported but the environments were considered to be 'warm-dry' or 'hot-dry'. Radiant heat was not considered but air velocity was measured at ~75 m.min-1. Heart rate was monitored continuously and expired air was collected using Douglas bags for the final two minutes of each test and was used to measure metabolic rate. Of particular interest in this study was the finding that a steady state heart rate was achieved in an air temperature (Ta) of 20˚C. Heart rate then remained consistent throughout the exercise period. At 35˚C (Ta), the attainment of steady state heart rate was delayed and heart rate increased as the exercise periods progressed. Steady state was not achieved during the final two exercise periods at 45˚C (Ta). Compared to the measurements at 20˚C (Ta), heart rate was approximately 10 beats.min-1 higher at 35˚C, and 20 beats.min-1 higher at 45˚C. These findings indicate that temperature has an independent effect on heart rate. The significance of these findings is greatly diminished by the fact that only three subjects participated in the study. Snook & Ciriello (1974) investigated the effects of heat stress on lifting, pushing and carrying tasks using a sample of sixteen male industrial workers. In particular the authors were interested in how much workers compensated for increased heat stress by modifying their lift frequency and workload. Wet bulb globe temperature (WBGT) was used to measure the working environment, as opposed to merely measuring ambient air temperature as in Kamon & Belding (1971). This gave a more detailed description of the components of heat stress (air, radiant and wet bulb temperature) that the workers were exposed to. Two environments were studied, moderate (17.2˚C WBGT) and hot (27˚C WBGT). The participants selected were all unacclimatised to work in hot conditions. The relative humidity was 45% (15°C natural wet bulb) in the moderate environment and 65% (25.5˚C natural wet bulb) in the hot environment. The lifting task consisted of lifting an industrial tote box from floor level to knuckle height and utilised a motorized frame that automatically lowered the box to the starting position again. Participants self-selected lift frequency or load weight (psychophysical approach) during the sessions depending on which groups they were assigned to. Heart rate and rectal temperature

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were monitored for all subjects and oxygen consumption was also measured for nine participants. It was found that in the hot environment, self-selected workload was significantly reduced by 20% for the lifting task (p = <0.01) and that heart rate and rectal temperature were significantly increased by 9 - 10 beats.min-1 and 0.2-0.3˚C (p = <0.01) respectively. It was noted that the reduction in workload was not sufficient to reduce heart rate and rectal temperature to levels found in the moderate environment. It was hypothesised that this was as a result of participants having a level of heat stress that they were prepared to work at and that heart rate and rectal temperature increases may be used to define this limit. It has been widely reported that an individual's ability to tolerate heat stress can be improved by acclimatisation (Buskirk & Bass, 1974). An acclimatised individual can work in a hot environment whilst maintaining a lower core temperature and heart rate than an unacclimatised individual. Evaporative cooling is improved by an earlier onset of sweating and a higher sweat rate (Sato et al., 1990). Hafez & Ayoub (1991) tested six male participants who performed a lifting test using a similar methodology to that described in Snook & Ciriello (1974). There were three environmental conditions (22˚C, 27˚C and 32˚C WBGT) that the subjects were acclimatised to over ten consecutive days. The precise environmental variables are described in table 1 below.

Table 1 Environmental variables (Hafez & Ayoub, 1991) WBGT (˚C) 22 27 32 Wet Bulb (˚C) Dry Bulb (˚C) RH (%)

20 26.7 53

24.5 33 49

29.4 38 52

Heart rate, rectal temperature and oxygen consumption were recorded throughout testing. Mean heart rate increased by 3 beats.min-1 during exposure to WBGT 27˚C when compared to exposure to an environment of WBGT 22˚C and by 7 beats.min-1 between 32˚C and 27˚C. Mean rectal temperature increased by 0.1˚C and 0.3˚C respectively between the three environments. When plotted, the increase in heart rate and rectal temperature in the three environments described a curvilinear relationship. There was a significant (p = <0.01) interaction effect between temperature at a given lift frequency and amount of weight selected to lift. The most pronounced reductions in workload occurred between 27˚C and 32˚C and at lift frequencies of 3 lifts.min-1 and 6 lifts.min-1. At a frequency of 3 lifts.min-1 there was an 18.3% reduction in weight lifted (25.6 kg - 20.9 kg) between 27˚ C and 32˚C. At 6 lifts.min-1 there was a 21.5% decrease in weight lifted (20.37 kg - 16.06 kg) between the same environments. Reductions in the amount of weight selected to lift at 27˚C WBGT were smaller (7.7% compared to 20%) than those reported by Snook & Ciriello (1974). The authors speculated that the younger participant sample and their acclimatisation status might have contributed to some of the differences reported in the results. The authors concluded that acclimatised individuals, can work at the same rate in a hot environments up to 27˚C WBGT as in a moderate environment (22˚C WBGT) without imposing intolerable thermal strain. They suggested however, that individuals working in hotter environments (specifically 32˚C WBGT) should reduce the weight of the load lifted or take longer rest periods. Further research was recommended in order to identify the precise temperature at which reductions in workload should occur. It was suggested that work/rest schedules at elevated temperatures should also be investigated. It should be noted here however, that the humidity ranges investigated were within a very narrow range and extremes were not investigated. The results of these studies are summarised in Table 2.

7

Table 2 Manual handling in hot environments: main studies and their findings

Authors n sex(m/f)

age (yrs)

Task Environment IndependentVariables

Dependent Variables

Parameters Duration Results

Kamon & Belding (1971)

3 m 20-24

walking 4,5 km.hr-1

0,4% grad 10,15,20 kg carrying 4,5km.hr-1

0,4% grad 10,15,20 kg sitting

neutral DB 20˚C WB 15˚C warm-dry DB 35˚C WB 20˚C Hot-dry DB 45˚ C WB 25˚ C

speed, gradient, load, environ.

metabolic rate

HR O2 consumption

65 minutes (5 min rest, 10 min warm-up, 45 min work)

at 30˚ C - HR, 10 beats.min-1 ↑ vs. 20˚ C at 45˚ C - HR, 20 beats.min-1 ↑ vs. 20˚ C

Snook & Cirrello (1974)

16 m

18-56 Average =35

lifting 20 inches 45, 55lbs pushing 50 ft horiz carrying 7,14 ft horiz 45, 55lbs

moderate 17.2˚C WBGT (DB 21.5˚C WB 15˚C) hot 27˚C WBGT (30.3˚C DB 25.5˚C WB)

environ., lift height, load, distance environ., lift height, frequency,

frequency load

HR Rectal temp 02 consumption

40 minutes

Lifting Task Load 20% ↓ HR, 10 beats.min-1 ↑ Tr ↑ 0.3˚ C at hot vs. moderate

Hafez & Ayoub (1991)

6 m Average =22.2

lifting a box floor toknuckle height

(DB 33˚C

22˚ C WBGT (DB 26.7˚C WB 20˚C) 27˚C WBGT

WB 24.5˚C) 32˚ C WBGT (DB 38˚C WB 29.4˚C)

environ. frequency

load

HR Rectal temp 02 consumption

40 minutes (3-6 lifts.min-1) 2 hours (0.1 lifts.min-1)

at lift frequency of 3lifts.min-1 load 18% ↓ at 32 vs. 27˚ C load 21.5% ↓ at 32 vs. 22˚ C HR, 7beats.min-1 ↑at 32 vs. 27˚ C Tr 0.3˚ C ↑ at 32 vs. 27˚ C

8

1.6 COLD AND IMPLICATIONS FOR MANUAL HANDLING

There is only a very small amount of literature reviewing the effects of cold on manual handling. Where appropriate, research that may have implications for manual handling in cold has been reviewed, but there is not enough information at present to determine what effect working in a cold environment has on manual handling tasks. For the purposes of this literature review a cold environment has been defined as an environment above 0°C and below 16°C. This limit was set as it is outside the scope of this study to investigate the potential additional effects that the addition of cold weather personal protective equipment (PPE) (e.g. hobbling effects, inappropriate selection of PPE resulting in excessive heat gain etc.) may have on manual handling. It should be noted however, that with appropriate PPE selection, many of the deleterious effects of working in a cold environment can be avoided (Holmer, 1994). Unfortunately, a worker dressed for thermal comfort at rest or for working at light intensities may be overdressed when working at high intensities (British Occupational Hygiene Society [BOHS], 1990). In this case, the additional layers of clothing may prevent heat loss leading to a rise in core temperature. Hagberg et al (1995) proposed that cold acted in two ways to affect the risk of musculoskeletal disorders: directly (effects on body structures) and from secondary effects resulting from PPE etc. During exercise, metabolic responses to cold exposure (compared to a thermal neutral environment) include reduced lipid mobilisation and higher levels of blood lactate (Doubt, 1991). Glucose use may be slightly higher (Doubt, 1991) and Blomstrand et al. (1986) reported greater use of glycogen in muscle cooled to 28° - 29°C compared to muscle at 35°C (Doubt, 1991). Edholm (1969) also identified an increase in urinary output in the cold, a phenomenon known as cold diuresis. The increase in urine production is accompanied by a decrease in plasma volume (and concomitant increase in blood viscosity). These changes have been reported to lower physical work capacity (Gronberg, 1991). Of particular interest in manual handling studies are the effects of cold on the hands. The extremities are anatomically and physiologically susceptible to cooling as they have a small muscle mass, large surface area to volume ratio and the hands are affected immediately by the reduction in blood flow caused by vasoconstriction. Physiological amputation is a phenomenon that occurs as a result of a declining internal temperature. It is a result of severe vasoconstriction of the blood flow to the extremities in order to conserve the heat flow to the core (Raman and Roberts, 1989). Vangaard (1990) showed that when participants were exposed to an environmental air temperature of 8°C the effect of the blood flow to the hand was identical to that when compared to a completely occluded hand. This has obvious implications for manual dexterity, the strength and sustainability aspects of manual dexterity, are of particular interest to manual handling tasks. A gradual loss of manual dexterity is experienced with the decline in temperature of various physiological structures including skin, muscle, receptor, nerve and joint temperatures. There is a reduction in nerve conduction velocity (De Jong et al., 1966) that drops strongly at a nerve temperature below 20˚C and is effectively blocked at 10˚C (Vangaard, 1975). There is also a loss of sensibility in the surface sensory receptors at a local skin temperature of around 6-8˚C (Morton & Provins, 1960). This affects tactile performance and consequently the ability to sustain a firm grip on an object. A decrease in joint mobility occurs as synovial fluid becomes more viscous at temperatures around 24°C and below (Heus et al., 1995). Strength and sustainability are also affected by declining temperatures. Loss of dexterity is accompanied by a loss of maximal force output and a reduced time to exhaustion on dynamic power tasks. A muscle temperature of 38°C is optimal for work requiring maximal force (Havenith, Heus and Daanen 1995). Psychological factors such as loss of attention due to pain or discomfort may

9

also play a role in decreased manual performance (Teichner, 1957). Local cooling caused by excessive draughts has also been shown to affect the myoelectric activity in shoulder and neck muscles of display screen equipment users (Sundelin and Hagberg (1992). Periodic vasodilation of the blood vessels in the hands has been reported when they are locally exposed to prolonged cold temperatures (Burton & Edholm, 1955). This phenomenon has been variously described as cold-induced vasodilation (CIVD), 'hunting reflex' and the 'Lewis effect'. Lewis (1930) reported that when the fingers were immersed in ice water, finger temperature dropped quickly to 0˚C but rose after approximately 10-15 minutes to around 5 - 6˚C. There then follows a cycle of temperature fluctuation that the author concluded was due to variations in local blood flow. Most of the work in this area has concentrated on cold-water immersion of the hands but some studies have noted a similar, though less pronounced, response in cold air environments (Kramer & Schulze, 1948; Blair, 1952). The brief increases in blood flow to the hands may result in increased manual dexterity for a short while as the heat input to the hand is only temporarily increased. This increase in performance is likely to be short lived due to the cyclic nature of CIVD. Cold injuries to the extremities can occur if inappropriate risk assessments are conducted. Examples of this may include handling of frozen produce in warehouse distribution centres whilst wearing inappropriate or no PPE or accidental contact of an exposed skin surface with a cold surface. Fritz and Perrin (1989) describe frostnip as a reversible injury that occurs as a result of an ice crystal formation on the skin’s surface. The skin itself does not actually freeze. Typically it develops painlessly, although a sudden blanching of the skin can be observed. Frostbite is more severe and occurs when tissue fluids freeze (Asahina 1966). During prolonged freezing at a relatively low temperature ice crystals begin to form in the extra-cellular electrolytes. This leads to a concentration of electrolytes, which in turn leads to osmosis of the remaining water from the cell eventually leading to cell death (Whittaker 1972). Non-freezing cold injuries due to exposure to temperatures between 1 - 15˚C may lead to nerve damage (peripheral vasoneuropathy) (Parsons, 1993). Piedrahita et al (2004) conducted a cross-sectional epidemiology study to explore the relationship between musculoskeletal symptoms and cold exposure in a large meat processing company. They determined that there was a statistically significantly higher prevalence of musculoskeletal problems amongst cold exposed workers (Ta approximately 2°C) compared to workers from less severely exposed areas (range +8°C to 12°C). Although the association between cold exposure and musculoskeletal problems is demonstrable, the mechanism by which it occurs is not clearly defined. Cold has been shown to negatively affect diffusion of fluid in the inter-vertebral disc when combined with heavy work and/or static posture (cited by Hildebrandt et al 2002). As stated above, investigations into the effects of cold environments on manual handling tasks have been limited, especially at temperatures likely to be encountered in the cold food industry. Emmett & Hodgson (1993) compared the cardiovascular responses of ten males whilst shovelling snow in thermal neutral, cold (4.9 ± 1.3˚C) and cold with wind (4.8 ± 1.3˚C and 1.9 m.s-1) environments. Heart rate was significantly lower (p = <0.05) in the cold/wind environment compared to the thermal neutral environment and post-shovelling systolic blood pressure was significantly higher (p = <0.05). The authors hypothesised that the reduction in heart rate may be a protective mechanism against excessive cardiovascular strain caused by the increase in systolic blood pressure. It was noted however that participants with higher body fat percentages exhibited higher mean cardiovascular responses. This may be partly due to the greater insulative effect of body fat resulting in less efficient heat loss.

10

Exercise in the cold will increases metabolic heat production, which offsets the heat debt due to working in the cold. However, exercise also increases peripheral blood flow (vasodilation) that will increase heat loss to the environment. Whether the exercise alleviates or exacerbates heat debt during cold exposure depends upon a number of factors including PPE worn, mode of activity and exercise intensity. Recent research shows that when acute exercise leads to fatigue without depleting glycogen stores, vasoconstriction responses to the cold are impaired and heat conservation is decreased (Young and Castellani 2001). Lifting large weights at low/moderate frequencies may result in this effect whilst working in the cold. Oska et al 2002, investigated the effects of repetitive work in thermal neutral and cold conditions on forearm electromyogram (EMG) and fatigue. It was hypothesised that cold and repetitive work when experienced together causes higher EMG activity than repetitive work only, thereby creating a higher overall risk of injury. It was determined that work in the cold did indeed result in higher EMG activity and fatigue than the same work in thermal neutral conditions. From the literature reviewed, the lack of research into the direct effects of the thermal environment on manual handling tasks is apparent. Whilst much research has been conducted into the effects of the thermal environment on various physiological structures it is not possible to extrapolate from this exactly what effect the thermal environment has, on manual handling in terms of physiological and psychological strain nor is it possible to derive best practice for conducting manual handling tasks in non-neutral thermal environments. Without this information it is difficult to perform a fully informed risk assessment. It is also not known whether people can self regulate and control any existing effects of manual handling occurring as a result of working in non-neutral thermal environments by decreasing productivity (in terms of decreased weight lifted) or whether these effects will manifest themselves in increased physiological and psychological strain. 1.7 HYPOTHESES – HOT STUDY

1. Frequency of lift will have a significant effect on all of the dependent variables. 2. Lifting tasks in hot thermal environments will impose a greater physiological load than

lifting tasks in thermal neutral environments. 3. The maximum acceptable weight of lift (MAWL) will decrease as the lifting frequency

increases regardless of environmental condition. 4. The MAWL will be lower in hot environments when compared to the maximum

acceptable weight in the thermal neutral environment for a given frequency. 5. Despite self-regulation of the MAWL, people will not adjust their maximum acceptable

weight of lift sufficiently to account for the increased physiological load imposed by the thermal environment. This physiological load will be manifested in increased core temperature and heart rate.

6. The higher WBGT value will impose a greater physiological load than the lower

WBGT value regardless of environment. 7. Rate of Perceived Exertion (RPE) will be a good indicator of physiological strain

occurring as a result of manual handling in hot environments.

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8. Heart rate will be a good indicator of physiological strain occurring as a result of manual handling in hot environments.

9. Core temperature will be a good indicator of physiological strain occurring as a result of

manual handling in hot environments. 1.8 HYPOTHESES – COLD STUDY

1. Frequency of lift will have a significant effect on all of the dependant variables. 2. The MAWL will be lower in cold environments when compared to the maximum

acceptable weight in the thermal neutral environment for a given frequency. 3. Heart rate will be lower in cold environments when compared to heart rate in the

thermal neutral environment for a prescribed frequency of lifting. 4. Heart rate will be lower in 0°C with the standard clothing ensemble than in 0°C with the

enhanced clothing ensemble for a prescribed frequency of lifting 5. Rate of Perceived Exertion will be lower in cold environments when compared to RPE

in the thermal neutral environment for a prescribed frequency of lifting 6. Rate of Perceived Exertion will be lower in 0°C with the standard clothing ensemble

than in 0°C with the enhanced clothing ensemble for a prescribed frequency of lifting 7. Core Temperature will be lower in cold environments when compared to Core

Temperature in the thermal neutral environment for a prescribed frequency of lifting 8. Grip strength will decrease in the cold environments when compared to grip strength in

the thermal neutral environments.

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2 METHODS

2.1 THE PHYSIOLOGICAL APPROACH OF ASSESSING MANUAL HANDLING TASKS

The physiological approach assesses markers of physical strain such as heart rate, oxygen uptake and energy expenditure so that working limits can be set that avoid the onset of excessive fatigue. Limits are usually set so that the loads selected can be lifted for extended periods (e.g. eight hour shifts) and, as such, are generally most applicable to high frequency, low-to-medium intensity tasks. In their review and subsequent laboratory study, Snook & Irvine (1969) demonstrated that physiological measures were often an unreliable method of limiting workload. This was most evident when baseline physiological measures were recorded with subjects exercising on treadmills or cycle ergometers. Baseline measures recorded using these protocols were largely non-transferable too more specialised tasks such as lifting where there may have been a substantial contribution from the upper-body. 2.2 THE PSYCHOPHYSICAL APPROACH TO ASSESSING MANUAL

HANDLING TASKS

The science of psychophysics examines the relationship that exists between subjective perceptions and physical stimuli or strain (Ayoub & Dempsey, 1999). Stevens (1958) described the process of psychophysics as 'seeking the laws that relate the responses of men and animals to the energetic configurations of the environment'. This phenomenon has been exploited in exercise science. Borg (1970) produced a rating scale of perceived exertion that is still in widespread use today.

6 7 8

9 1

1 1

1 1

1 1

1 1

1 2

Figure 1 Borg

Rate of Perceived Exertion (RPE)

NO EXERTION AT ALL

EXTREMELY LIGHT

VERY LIGHT

0

1 LIGHT

2

3 SOMEWHAT HARD

4

5 HARD (HEAVY)

6

7 VERY HARD

8

9 EXTREMELY HARD

0 MAXIMAL EXERTION

scale for rating of perceived exertion

13

Rate of Perceived Exertion is a subjective rating of how hard you feel your body is working. It is based on the physical sensations a person experiences during physical activity. Although RPE is a subjective measure, it has been shown to provide a fairly good indication of heart rate during physical activity (Borg 1988). Studies have been conducted to evaluate the use of the RPE scale as a means of self -regulating the intensity of various types of exercise. Eston et al 1987 found that RPE was at least as good a predictor of exercise intensity as heart rate in a running task and concluded that RPE can be used to predict relative metabolic demand, especially at higher work loads. Research has also been conducted specifically investigating the effectiveness of the RPE scale for evaluating manual handling tasks. RPE was found to have an almost linear relationship to oxygen consumption and heart rate when lifting or lowering loads (Asfour et al 1983) and was subsequently recommended as a reliable method of quickly and inexpensively assessing manual handling tasks in the field. Maw et al (1993) investigated ratings of perceived exertion in hot and cold environments and determined that at the same absolute intensity of exercise participants perceived work to be harder, felt worse and experienced greater thermal sensations in the hot condition compared to neutral and cool conditions.

When considering manual handling tasks, psychophysics makes three assumptions (Gamberale et al., 1987):

1. An individual is able to rate perceived effort in a lifting task. 2. They are able to produce an individually acceptable level of performance on

their task. 3. This level of performance will be safe from manual handling injuries.

However, as Karwowski (1996) argued, the validity of these assumptions has never been fully examined. In manual handling research, participants are often asked to establish a maximum acceptable weight of a lift. Participants are asked to perform a specified lifting task (or carrying, pulling, lowering etc.) at a set frequency. The participants are asked to imagine they are working on an incentive basis, as hard as they can (i.e. lifting as much as they can) without straining themselves or becoming unusually tired (Snook et al 1970). The participant adjusts the weight of the load they are handling until they decide that it would be acceptable to lift that load at the set frequency for a set period of time (usually eight hours). Based on experimental work of this nature, Snook (1978) published tables of maximum acceptable weights and forces that, after further investigation, were subsequently revised (Snook & Ciriello, 1991). These tables provide information for a number of manual handling tasks and account for variable load sizes, lift heights and horizontal distance of the load from the body. This data is utilized in manual handling guidance and HSE’s MAC tool. Many investigations have found that the psychophysical approach appears to produce reliable results for manual handling tasks characterized by low to moderate frequencies (Legg and Myles 1982, Mital and Manivasagan 1983, Aghazadeh and Ayoub 1985 etc). In a comprehensive review of the area of psychophysics and manual handling, Ayoub & Dempsey (1999) identified a number of advantages and disadvantages associated with this assessment approach. In its favour, the authors cited its ability to assess realistic work tasks and the validity of the data that was collected using industrial workers as participants. This methodology can also be used to assess intermittent tasks and can integrate both biomechanical and physiological factors. The main limitations of the psychophysical methodology are that it is a subjective approach and that the assumption that selected loads are below injury thresholds is not validated. Furthermore, at low and high lifting frequencies, the selected loads may exceed limits imposed by biomechanical and physiological assessment alone. This assumes that limits set using biomechanical and physiological data are correct but this assumption remains unproven.

14

Psychophysics seeks to bridge the gap that exists between biomechanical and physiological assessment methods. The weights in Snook & Ciriello's (1991) tables have been found to exceed 'safe' spinal compression loads (NIOSH, 1981) at low lifting frequencies. At the other end of the continuum it is acknowledged that weights for high frequency lifts may not be valid for eight-hour shifts because they incur undue physiological strain. Mital et al. (1993) have published modified tables, incorporating biomechanical and physiological data, in an attempt to overcome the problems encountered at the high and low ends of the lift-frequency spectrum. 2.3 SITE VISITS

To ensure validity of the experimental conditions selected several site visits were conducted, prior to experimentation, within UK industry to characterise manual handling activities and the thermal environments that they are conducted in. At each visit, environmental measurements of air temperature, humidity and radiant temperature were taken. All the work places visited were indoors, so air velocity was assumed to be minimal (for the purposes of calculating WBGT) unless a noticeable draught was perceived as a result of an open door or similar. Notes of clothing/PPE worn and activity levels were also made. Employees were observed whilst carrying out their normal duties and weight of load, frequency of lifts, lifting height and duration of task were noted. Employees were only observed carrying out lifting and lowering tasks, as manual handling tasks involving other aspects of manual handling e.g. pushing/pulling tasks were outside the remit of this study. Details of the site visits conducted can be found in Appendix 2. A series of studies were designed to investigate the effects of hot and cold environments on manual handling (lifting tasks). The first experiment investigated the effects of hot/humid and hot/dry environments on lifting tasks; the second investigated the effects of a cold environment on a lifting task. For the sake of clarity, the two experimental designs, methodology, results, discussion and conclusions will be discussed separately from this point.

15

3 EXPERIMENT 1: ‘HOT’ EXPERIMENT

3.1 DESIGN

A, within-subjects, repeated measures design was used. Each participant took part in all of the fifteen test conditions. Exposure to each condition was randomised using an unbalanced Latin Square. Each participant was exposed to five environmental conditions and three lifting frequencies. To ascertain whether lifting tasks performed under equivalent WBGT values with different thermal environments induced similar or different effects one of the WBGT values resulted in two different thermal environments. The WBGT values used resulted in environments of hot/humid, hot/dry, warm/humid and warm/dry. Thermal neutrality was used as a control environment. Table 3 describes the environmental conditions and Table 4 describes the frequency of lift undertaken at each condition.

Table 3 Environmental conditions Environment Air temperature (°C) Relative humidity (%) WBGT (°C) Thermal neutral 21.9 ± 0.9 47.3 ± 5.5 17 Warm dry 29.9 ± 0.5 24.8 ± 1.2 22 Warm humid 30.5 ± 0.4 68.4 ± 2.1 28 Hot dry 38.7 ± 0.6 21.9 ± 1.1 28 Hot humid 37.4 ± 0.3 70.6 ± 2.5 34

Table 4 Lifting frequencies

Frequency Lifts.min-1

1 every 9 seconds 6.7 1 every 14 seconds 4.3 1 every 60 seconds 1

3.2 PROCEDURE

Ethical approval for this study was granted by Sheffield Hallam University (SHU). All participants were treated in accordance with the Helsinki Declaration 1964 and BASES ethical guidelines. They were given oral and written descriptions of the procedures involved (see Appendix 3 for the written description) and completed a medical questionnaire (see appendix 4) before giving written informed consent to continue. Participants with any previous history of musculoskeletal disorders were excluded from the study, as were participants with illness, disorders or diseases known to affect the thermoregulatory system (e.g. thyroid conditions). The participants reported to the environmental chamber at the Centre for Sport and Exercise Science (CSES), SHU. Height (stadiometer, Holtain, Crymych, UK), mass (Balance Scales, Avery, Birmingham, UK) and knuckle height (distance from floor of second metacarpo-phalangeal joint when standing relaxed) were measured. Participants were asked to abstain from alcohol for 24 hours prior to commencement of the study. Skin thermistors (Grant Instruments, Cambs. UK) were fixed to the body with Micropore tape (3M, USA) according to the Ramanathan 4 point measurement site for estimation of mean weighted skin temperature; at the chest (centre of pectoral region, midpoint between nipple and clavicle), arm (posterior aspect of the upper-arm, at the centre of the belly of the triceps), thigh (anterior aspect, over rectus femoris at midpoint of femur) and shin (anterior aspect of lower-leg, at midpoint of tibia). An aural bead thermistor (Grant Instruments, Cambs. UK) was fitted into the ear, micropore tape

16

was used to secure the bead, which was then insulated with cotton wool. A set of industrial ear defenders was then donned to provide insulation of the aural environment from external environmental conditions. All thermistors were connected to a data logger (Squirrel 1021, Grant Instruments, Cambs. UK) so that measurements could be recorded throughout testing. The aural thermistor was left in place for twenty minutes prior to the onset of experimentation to allow the sensor to reach equilibrium. A heart rate monitor was also worn (Polar 610, Polar, UK). Each participant was then clothed in a standard clothing ensemble (table 5). The clothing ensemble was chosen to replicate as closely as possible the clothing observed to be worn during the site visits. No gloves were worn. The estimated Clo value was designed to ensure that the participant was comfortable whilst standing in the thermally neutral environment.

Table 5 Standardised clothing ensemble and Clo values

Clothing Item Clo Underwear (shorts, socks as supplied by participant)

0.05

Working trousers (cotton/polyester) 9oz 0.25 Working jacket (cotton/polyester) 9oz 0.25 Safety boots 0.1 Estimated Clo of ensemble 0.65 3.3 ACCLIMATISATION

The first week was designated as an acclimatisation period and consisted of five one-hour sessions. Published literature has shown that this amount of exposure can provide in excess of 75% of an individual’s total adaptation to a particular environment (Parsons, 2003) with the final ~25% adaptation occurring over a further five days. The environmental chamber was set at 38°C and 70% relative humidity (this replicated the most hostile environment used in the experiment). Prior to entering the environmental chamber for the first time the participants were read a script detailing the test protocol (see appendix 5) and were also familiarised with the Borg 6-20 Rating of Perceived Exertion scale (Borg, 1970). The acclimatisation session was divided into rest, work and a final rest period and the participants were required to remain in the environmental chamber throughout the sixty minutes. Two twenty-minute rest periods were interspersed with a twenty-minute lifting task (described below). Drinking water was available throughout and participants were encouraged to drink regularly. 3.4 LIFTING TASK

A shelf in an industrial racking unit was set at the participant’s knuckle height. A plastic box (60 x 39 x 41 cm) was placed on the floor in front of the shelving unit at a fixed distance from it. The box was loaded with weights by the experimenter out of sight of the participant. The weights were concealed beneath a false box bottom so that the participants could not use visual cues to help determine the weight of the box at commencement of the task.

17

Figure 2 a) Shelving unit with adjustable shelf, b) box with false bottom concealing weight bags, c) box at end of session with weight added by the participant

The participants then lifted the box from the floor onto the shelf once every 14 seconds (4.3 lifts.min-1) in time with a metronome. This constituted one complete lift. On completion of the lift the participant stepped back and an assistant returned the box to its starting position (i.e. participants only lifted the box, no lowering was done by the participant). During the twenty minutes lifting period the participant was encouraged to make adjustments to the box weight by either adding or removing small canvas bags of ball bearings ranging in weight from 1kg to 10kg. The aim of this weight adjustment period was to arrive at a box weight that the participant found to be acceptable to lift for a standard eight-hour shift (including breaks etc.) in an industrial setting without the individual becoming unduly fatigued. This procedure is similar to the psychophysical approach adopted by Snook (1970). 3.5 EXPERIMENTAL SESSIONS

The 15 experimental sessions were conducted at the same time of day (to avoid any circadian rhythm influence) on consecutive days, Monday to Friday. The participants were clothed and equipped as in the acclimatisation sessions and then rested for 20 minutes prior to commencement allowing their aural thermistor to stabilise. During this period the shelf heights were set and box starting weights were randomised. The participant was informed of the lifting frequency for the session, but was not aware of the environmental conditions nor the starting weight of the box. Where two participants were tested simultaneously they were informed that their starting box weights were different thus removing any competitive element from the session.

18

Figure 3 a) Lift start, b) lift completion, c) assistant returns box to start

The participants entered the chamber and all recording equipment was started. They then lifted the box onto the shelf at the prescribed frequency for 35 minutes (as described in the section titled ‘Lifting Task’. An assistant again returned the box to its starting position). Adjustment of the box weight was allowed for the first 20 minutes using the bags of ball bearings provided. After 20 minutes no further adjustments were permitted and the participants continued lifting for a further 15 minutes at that particular box weight. RPE was recorded every five minutes throughout the session and the participants were encouraged to convey this information discreetly so as not to influence other lifters present. Heart rate readings were also taken manually every five minutes. To ensure the health and safety of the participants a second experimenter was always present in the chamber. Drinking water was available at all times. After 35 minutes the test was stopped and the participants were removed to a warm-down room and any instrumentation was removed at this point. The final box weight was recorded as the maximum acceptable weight of lift (MAWL) for the session. 3.6 PARTICIPANTS

Male participants were used to avoid menstrual effects and any confounding variables occurring as a result of differences in anthropometrics between males and females. 12 male participants were recruited by general notice and by advertisements on the university’s website. Participant characteristics are presented in table 6.

Table 6 Participant characteristics (means and standard deviation)

N Age (y) Stature (m) Mass (kg) Knuckle Height (m)

12 25.2 (±5.7) 1.73 (±0.07) 74.9 (±11.9) 0.77(±0.04)

3.7 ENVIRONMENTAL MEASUREMENT

Air temperature was measured using a temperature probe (general purpose thermistor CS-U, Grant Instruments, Cambs., UK), accurate to ±0.2˚C between 0˚C and 70˚C. Relative humidity was measured using a humidity sensor (Rotronic Hygroclip humidity and temperature sensor, Rotronics Instruments UK Ltd., West Sussex, UK), accurate to ±1.5% RH between -40˚C and 85˚C.

19

The probes were positioned behind the participants at approximately 1.1 m distance from the floor. A data logger (Squirrel 1021, Grant Instruments, Cambs. UK) recorded data every 10 seconds. All data from the loggers were subsequently downloaded into Microsoft Excel (via Squirrelview v 1.03) for analysis. 3.8 WITHDRAWAL CRITERIA

Withdrawal criteria was set at an aural temperature of 38.5°C. Heart rate was monitored simultaneously and consideration given to removing the subject if this exceeded 85% of their age-predicted maximum (based on the other objective and subjective measurements). 3.9 ANALYSIS

A two-factor ANOVA with repeated measures on both factors was conducted on each of the five dependent variables using SPSS v11. α was set at 5%.

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4 RESULTS

4.1 ASSUMPTIONS

The four dependent variables (Heart rate (HR), Core temperature (Tc), RPE and MAWL) were each individually analysed using a two-way, repeated measures ANOVA with 12 subjects. The two within subject factors are environment (ENV) and frequency (FREQ) together with the interaction (ENV*FREQ). There are five levels in ENV and three in FREQ. The assumptions underlying this type of analysis are that data are normally distributed and display sphericity (homogeneity of covariance). These assumptions are tested in SPSS using a Kolmogorov-Smirnov and Mauchly’s test respectively. 4.2 HEART RATE

The mean end heart rate (average of the last three readings) was calculated for each session. Figure 4. describes the average end heart rate and standard deviation of the participants in each lifting frequency by each environmental condition. Figure 5. describes the change in heart rate from the baseline reading to the end measurement

60

80

100

120

140

160

180

Thermal Neutral

Warm Humid Warm Dry Hot Humid Hot Dry

1/60s 1/14s

1/9s

Figure 4 Mean end heart rate for three lifting frequencies

21

-20

0

20

40

60

80

100

Thermal Neutral

Warm Humid Warm Dry Hot Humid Hot Dry

1 per 60 sec 1 per 14 sec 1 per 9 sec

Figure 5 Mean change in heart rate for three lifting frequencies in all environmental conditions

4.2.1 Heart rate change – ANOVA (analysis of variance)

Only one data set out of the fifteen conditions was found to be non-normally distributed. In order to determine whether baseline conditions were equal for all sessions an ANOVA was run on the starting heart rate. A significant effect of environment on base line heart rate data was found (P<0.005). This means that it cannot be assumed that any differences apparent in end heart rate are due to the effects of the environment and/or lifting frequency. For this reason, the change in heart rate over the experimental session was used. The differences in HRchange between each environmental condition at each lifting frequency and their interactions were investigated. The F values for the main analysis and significance values are detailed in Table 7.

Table 7 Results of ANOVA for heart rate change Source Df F Sig (P value) Environment 4 30.087 0.000 Frequency 2 79.513 0.000 Participant 11 26.637 0.000 Environment*Frequency 8 1.810 Not Significant

There were significant main effects for environment, Frequency and Participant. The interaction effect was not significant. 4.2.2 Heart rate change – post hoc tests

Post hoc analysis was done using Tukey’s pairwise comparisons. The results for ENV are detailed in Table 8.

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Table 8 Significance values from Tukey’s pairwise comparisons for heart rate change

Warm dry Warm humid Hot dry Hot humid

Thermal neutral Not Significant Not Significant Not Significant P<0.01

Warm dry Not Significant Not Significant P<0.01

Warm humid Not Significant P<0.01

Hot dry P<0.01 There was a significant change in heart rate between the hot humid condition and every other environmental condition. The results for FREQ are detailed in Table 9.

Table 9 Significance values from Tukey’s pairwise comparisons for heart rate change

1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds P<0.01 P<0.01 1 Lift every 14 seconds P<0.01

The frequency of lift had a significant effect on heart rate at each lifting frequency. 4.3 CORE TEMPERATURE

The mean end core temperature (average of the final 3 readings from the experimental session) was calculated. Figure 6. shows the end mean core temperature and standard deviation of the participants in each lifting frequency by each environmental condition.

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36

37

38

39

Thermal Neutral Warm Humid Warm Dry Hot Humid Hot Dry

1/60s 1/14s

1/9s

Figure 6 Mean end core temperature for three lifting frequencies

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Figure 6b. shows the change in core temperature and standard deviation of the participants in each lifting frequency by each environmental condition.

-1

0

1

2

Thermal Neutral Warm Humid Warm Dry Hot Humid Hot Dry

1 per 60 sec 1 per 14 sec 1 per 9 sec

Figure 6b Mean change in core temperature for three lifting frequencies

4.3.1 Core temperature change – ANOVA (Analysis of Variance)

In order to determine whether baseline conditions were equal for all sessions an ANOVA was run on the starting core temperatures. A significant effect of environment on baseline core temperature was found (P<0.005). It therefore cannot be assumed that any differences apparent in end absolute core temperature are due to the effects of the environment and/or lifting frequency. For this reason the increase in core temperature was used to determine the effects of the environment and lifting frequency on core temperature. Table 10 shows the main effects.

Table 10 Results of ANOVA for core temperature change

Source df F Significance (P Value)

ENV 4 43.078 0.000 FREQ 2 57.735 0.000 PARTICIPANT 11 11.554 0.000 ENV*FREQ 8 5.4 0.000

There is a significant interaction effect and significant main effects for both ENV and FREQ. The effect of participant was also significant.

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4.3.2 Maximum core temperature – post hoc tests

Post hoc analysis was done using Tukey’s pairwise comparisons. The pairwise comparisons for environment are detailed in Table 11.

Table 11 Results of Tukey’s pairwise comparisons for Tcchange for environment Warm dry Warm humid Hot dry Hot humid

Thermal neutral Not Significant P<0.01 P<0.01 P<0.01

Warm dry Not Significant Not Significant P<0.01

Warm humid Not Significant P<0.01

Hot dry P<0.01

The change in core temperature as a result of lifting in the hot humid environment was significantly different to lifting in any other environment. Significant differences were also found between the hot dry and thermal neutral environment and the warm wet and thermal neutral environment. The results for FREQ are detailed in table 12.

Table 12 Significance Values from Tukey’s pairwise comparisons for core temperature

change 1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds P<0.01 P<0.01 1 Lift every 14 seconds P<0.01

The frequency of lift had a significant effect on change in heart rate at each lifting frequency. 4.4 RATE OF PERCEIVED EXERTION (RPE)

The mean end RPE values for each session were taken. Figure 7 shows the end average RPE value and standard deviation of the participants in each lifting frequency by each environmental condition.

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6

20

Thermal Neutral Warm Humid Warm Dry Hot Humid Hot Dry

1/60s 1/14s

1/9s

Figure 7 Mean end RPE for three lifting frequencies 4.4.1 Rate of perceived exertion – ANOVA

Eleven of the 15 data sets were non-normally distributed and no transformation of the data was able to rectify the problem. However, ANOVAs are robust to the violations of this assumption and as there are no two-way non-parametric tests available an ANOVA was used but a higher significance level (p<0.01) was accepted. The results of the main analysis for RPE are detailed in table 13.

Table 13 Results of ANOVA for rate of perceived exertion

Source df F Sig (P Value) ENV 4 15.750 0.0001 FREQ 2 25.945 0.0001 PARTICIPANT 11 29.917 0.0001 ENV*FREQ 8 1.448 Not significant

There were significant main effects for ENV and FREQ. The effect of participant was also significant. The interaction effect was non-significant.

4.4.2 RPE – post hoc tests

Post hoc analysis took the form of pairwise comparisons using Tukey’s tests. The results for ENV are detailed in Table 14.

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Table 14 Results of Tukey’s pairwise comparisons for RPE (ENV) Warm dry Warm humid Hot dry Hot humid

Thermal neutral Not Significant Not Significant Not Significant P<0.01

Warm dry Not Significant Not Significant P<0.01

Warm humid Not Significant P<0.01

Hot dry P<0.01

The hot humid environment resulted in a statistically different final RPE environment than any other environment. Non of the other environments significantly affected the final RPE. The results for FREQ are detailed in table 15.

Table 15 Results of Tukey’s pairwise comparisons for rate of perceived exertion

(frequency) 1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds P<0.01 P<0.01 1 Lift every 14 seconds P<0.01

Lifting frequency had a significant effect on the RPE at each lifting frequency. 4.5 MAXIMUM ACCEPTABLE WEIGHT OF LIFT (MAWL)

The mean end MAWL values for each session were taken. Figure 8. describes the end average MAWL value and standard deviation of the participants in each lifting frequency by each environmental condition.

0

10

20

30

40

Thermal Neutral Warm Humid Warm Dry Hot Humid Hot Dry

1/60s 1/14s

1/ 9s

Figure 8 Mean end MAWL for three lifting frequencies

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Table 16 shows the mean percentage change in the MAWL by environment and lifting frequency from thermal neutral.

Table 16 Mean percentage change in maximum acceptable weight of lift by environment

Mean Percentage Change in MAWL by Environment and Frequency (%)

1/60s 1/14s 1/ 9s Warm humid -1.4 -2.3 0.4 Warm dry 4.4 -0.8 -1.3 Hot humid -1.8 -7.7 -11.2 Hot dry -5.2 -1.2 -5.2

Table 16. shows that the decrement in MAWL was highest at the highest lifting frequency and that the hot humid condition resulted in the biggest decreases in the MAWL for two of the lifting frequencies, but the hot dry resulted in the biggest decrease in MAWL for the one lift a minute lifting frequency. 4.5.1 Maximum acceptable weight of lift – ANOVA

All data for MAWL were found to be normally distributed. The values for the main analysis for MAWL are detailed in table 17.

Table 17 Results of ANOVA for maximum acceptable weight of lift Source Df F Sig (P Value) ENV 4 4.717 0.05 FREQ 2 18.181 0.000 PARTICIPANT 11 142.488 0.000 ENV*FREQ 8 0.754 Not significant

There were significant main effects for both ENV and FREQ. The effect of participant was also significant. The interaction effect was non-significant. 4.5.2 Maximum acceptable weight of lift – post hoc tests

Post hoc analysis took the form of pairwise comparisons using Tukey’s tests. The results for ENV are detailed in table 18.

Table 18 Results of Tukey’s pairwise comparisons for maximum acceptable weight of

lift (Environment) Warm dry Warm humid Hot dry Hot humid

Thermal neutral Not Significant Not Significant Not Significant P<0.05

Warm dry Not Significant Not Significant P<0.01

Warm humid Not Significant

Not Significant

Hot dry Not Significant

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The MAWL was found to be significantly different in the hot humid environment when compared to the thermal neutral and warm dry conditions. The results for FREQ are detailed in Table 19.

Table 19 Results of Tukey’s pairwise comparisons for MAWL (Frequency)

1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds Not Significant P<0.01 1 Lift every 14 seconds P<0.01

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5 DISCUSSION – HOT EXPERIMENT

This study investigated the effects of warm and hot environments on participants conducting a manual-handling task (box-lifting in this case) using a combination of physiological (objective) and psychophysical (subjective) methods. Figure 9 shows how the environmental conditions selected for this study compared with those that have been used in past studies.

17.2

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32 17.5

22.5

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17.5

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20 22 24 26 28 30 32 34 36 38 40

Dry bulb /°C

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Relative humidity

Snook and Ciriello Hafez and Ayoub Hot Experiment (warm environments)

Hot Experiment (hot environments)

Figure 9 Shows the environmental parameters and WBGT numbers used in past studies and in the hot experiment study

The present experiment (Hot Experiment) replicated two of Snook and Ciriello’s conditions and had a similar WBGT (27°C) to Hafez and Ayoub although the environmental conditions were different. Higher clothing levels were used in this study (0.65) than those reported by Hafez and Ayoub (0.12 clo) and Snook and Ciriello (0.47 clo) but this level of clothing was felt to be more representative of what was worn in UK industry (see appendix 2). The end lift frequencies used were determined as a result of the pilot studies. Acclimatisation sessions were run at 35°C, 70% RH stabilising the MAWL at all 3 lift frequencies in a thermally neutral environment using the 1 lift/min and 4.3 lifts/min frequencies. However, a problem was

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encountered at the MAWL stabilisation of 12 lifts/min (1 lift every 5 seconds). It became apparent that this was an impractical lift frequency to conduct, especially in the heat. It required considerable coordination between lifter and lowerer to effect the movement and required more or less continuous activity. This resulted in considerable discomfort even in a thermally neutral environment. As the published MAWL's (Snook & Ciriello, 1991) for this frequency all violate the 33% VO2max physiological lifting limit for all industrial workers, it was felt that decreasing this lifting frequency would ensure that the results would be more applicable to UK industry. Additionally there was also the practical concern that the participants did not have adequate time to keep hydrated during the session. For these reasons the 12 lifts/min frequency was replaced with a 6.7 lifts.min-1 (1 every 9 seconds) . When examining the mean end heart rate data for this hot experiment the effect of the environment on the maximum heart rate elicited was apparent, with the hot humid environment resulting in the largest maximum heart rates followed by the warm humid and warm dry environments. Upon statistical analysis of the baseline measurements however, an influence of environment could already be seen. As there was already a statistically significant difference in the heart rate prior to the participants beginning their lifting task, any further statistical significance post lifting task on the maximum heart rate could not be attributed to the effects of the lifting task in that environment. Therefore, the main effect of environment (ENV) on change of heart rate was examined. It was shown that the hot humid (HH) environment imposed a significantly greater physiological load on the cardiovascular system than any of the other four environments. The differences were greatest when HH was compared to thermal neutral (TN). The 1 lift.min-1 frequency was found to elicit a significantly higher change in heart rate from the baseline measurement when compared to both of the other lifting frequencies. There were also significant differences between 4.3 lifts.min-1 (1 every 14 seconds) and 6.7 lifts.min-1 (1 every 9 seconds). The change in heart rate over the lifting task suggest that the participants overestimated, their lifting capabilities at all lifting frequencies and environments. Looking at maximum heart rates attained over the sessions, it is unlikely, for instance, that the mean HRmax (152.3 beats.min-1) at 6.7 lifts.min-1 (1 every 9 seconds) in hot humid environment could be sustained over the course of an 8 hour shift. The general trend when examining the HR responses at 6.7 lifts.min-1 (1 every 9 seconds) was that there was a plateau after the end of the MAWL stabilisation period except in the HH environment where HR continued to rise throughout the session. At 4.3 lifts.min-1 (1 every 14 seconds), HRmax reached a plateau in all environments suggesting that this frequency may represent an upper limit for manual handling in HH environments. Indeed, Snook & Ciriello (1991) have stated that tasks conducted at 4.3 lifts.min-1 (1 every 14 seconds) generally resulted in individuals remaining within physiological guidelines and that 94% of industrial tasks were performed at this frequency or slower. It appears that participants are unable to judge the extra physiological strain placed on the cardiovascular system as a result of working in non-neutral thermal environment. This would suggest that leaving people in a work environment to self pace their work may not be a reliable method of protecting the worker from physiological strain. As with heart rate the baseline reading of core temperature showed that environment had a significant effect. For this reason, the change in core temperature from the baseline to the end of the experimental session was analysed. Tcmax generally increased throughout the session in HH for both 6.7 and 4.3 lifts.min-1 (1 every 14 seconds) indicating an inability on the part of the participants to compensate for the thermal strain imposed on them by the lifting task in the non-neutral thermal environments. The increase in core temperature over the session was higher in the hot humid condition than in any other condition. The core temperature increases were also significantly different in the warm wet and hot dry environments from the thermal neutral

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environment. It is interesting to note that the hot dry and warm wet environment shared the same WBGT value and do indeed seem to impose similar levels of physiological strain in terms of increase in core temperatures when considering lifting tasks. Again, as with the heart rate measurements, the continuing increases in core temperature after the MAWL stabilisation period demonstrate that self regulation in the work place is not a viable option for controlling physiological strain occurring as a result of manual handling tasks in non-neutral thermal environments. It should be remembered that aural temperature was measured in the present study, a method that usually results in lower readings than rectal measurement. The tissues of the deep body allow greater heat storage due to the thickness and insulative properties of the trunk. It could be argued that the Tcmax (in terms of the deep body) was probably higher than the aural reading indicating that the participant was actually more at risk of injury than the aural temperature suggested. Conversely, the aural reading may provide a better indication of brain temperature (Muir 2001), a factor which has been implicated in central fatigue theory (Cheung & Sleivert, 2004; Nielsen & Nybo, 2003). Interpreting the RPE data is problematic because of the violations of the underlying assumptions of the main ANOVA. No transformation was able to overcome the problem of non-normal distribution so the findings should be treated with caution. There were significant main effects for ENV and frequency (FREQ). RPE was significantly different (p = <0.01) in HH when compared with all other environmental conditions. It was also significantly different at all lifting frequencies. The participants appeared to be extremely conservative with their interpretations of perceived exertion despite extensive familiarisation with the RPE scale during the acclimatisation phase. It is possible that, despite attempts to keep responses private from other participants, these may have been influenced in some cases by a ‘macho’ effect. It should be noted however, that this effect is likely to occur in industry with similar results. It is perhaps not surprising that there were no significant differences in RPE over the majority of the experimental conditions. The participants were instructed to lift at a level that they could sustain for an eight-hour shift without unduly stressing themselves. The lack of significant differences between the RPE’s at different environments may reflect that they believe that they have selected an appropriate MAWL. The fact that their physiological measurements continued to rise however may show that people are unable to accurately judge a ‘comfortable’ weight to lift in thermal extremes. A further issue with the RPE value occurred when participants were advised to give an overall feeling of exertion (i.e. not focusing on any particular body area or specific discomfort) and to consider this in terms of an average over the lifting cycle. This appeared to be easier to do at 4.3 and 6.7 lifts.min-1 (1 every 9 seconds) where, although still intermittent, the frequencies could be considered high enough, to be thought of as ‘continuous’. At these frequencies an average level of exertion was more readily identified as opposed to 1 lift.min-1 where the participant would lift for approximately 2.4 seconds and stand relaxed for the remainder of the minute. Previous studies have shown RPE to be a reliable indicator of strain whilst undertaking manual handling tasks. Asfour et al (1983) showed RPE to be a reliable method of indicating the severity of manual handling tasks in industry. The lowest lifting frequency that was tested however was three lifts a minute. RPE has been shown to provide a good estimation of the actual heart rate during physical activity (Borg 1998). Glass et al (1994) however suggested that whilst RPE was closely related to metabolic intensity it was not a valid indicator of cardiovascular strain during exercise in

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thermally extreme environments. This would seem to be the case in this study. The high maximum heart rates were not always reflected with correspondingly high RPE values. Borg (1998) showed that a high correlation exists between a person’s RPE and their heart rate, with the heart rate being approximately 10 times greater than their RPE value. This work was done at thermally neutral conditions however. Despite some significant differences in the analysis it would seem that the RPE scale is not a sensitive enough tool to regulate manual handling in thermal environments. The maximum acceptable weight of lift (MAWL) was the box weight selected after 20 minutes of lifting and represented the amount of weight that a participant felt they would be happy to lift over the course of a normal 8 hour shift. This is an example of the psychophysical strategy utilised by Snook & Ciriello (1974) where the lifter uses their own subjective assessments to regulate the workload. There were significant main effects for both ENV (environmental condition) and FREQ (lifting frequency). Post-hoc tests however only showed significant differences between the hot humid environment and the thermal neutral and warm dry environment. Tukey’s test is known to be conservative however and may have lacked the power to detect meaningful differences. On examination of the main effect for FREQ, Tukey’s tests found significant differences for MAWL between 6.7 lifts.min-1 (1 every 9 seconds) and the two other frequencies (p = 0.001). Interestingly there was no significant difference between MAWL at 1 lift.min-1 and 4.3 lifts.min-1 (1 every 14 seconds). Mean values for MAWL varied by less than 2 kg across environments and by less than 4 kg across lift frequencies. This suggests that the participants selected a relatively consistent box-weight regardless of their environment or how often they had to lift. The percentage decreases in MAWL when comparing all non-neutral thermal environments to the thermal neutral environment are smaller than those reported previously (Snook & Ciriello, 1974; Hafez & Ayoub, 1991) and may be partly explained by differences in acclimation status, environments and frequencies used in the various test protocols. Hafez & Ayoub (1991) included a 0.1 lift.min-1 (one lift every ten minutes) in their protocol for instance, a frequency that would be expected to elicit a far greater MAWL than 3 lifts.min-1 (their fastest lift). The participants in the present study were mostly students without specific industrial backgrounds and many adopted a cautious approach to the lifting task because of a perceived injury risk (Some participants were particularly protective of their lower backs despite being screened for any prior injuries). It should be noted however that these reasons for discrepancies between the different studies have implications for the work place. Within the UK workforce, there will be differences in age, acclimatisation, health status etc., and that whilst these differences will undoubtedly exist between workers there will also be changes within individuals over the course of working life. Long periods of absence from work due to holidays or sick leave for example may result in an individual losing acclimatisation. Therefore any risk assessments completed to assess the level of risk associated with manual handling in non-neutral thermal environments need to be reviewed as and when circumstances change. For example, changes in work practices, employees return from a prolonged absence i.e. two weeks more due to either holiday or illness or new/pregnant employees are present in the workforce. On comparison with the lifting tables published by Snook & Ciriello (1991) the lifters in the present study averaged just above the 25th percentile (across all environments) at 1 lift.min-1 and just below the 50th percentile for the other two frequencies. It should be noted that the MAWL values at the 50th percentile (for 6.7 lifts.min-1 (1 every 9 seconds)) are highlighted as values that may cause the lifter to exceed the physiological limit of 33% VO2max. Coupled to this, the

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finding that MAWL values remained relatively consistent across conditions indicates that the psychophysical strategy (if used in isolation) may be a poor method of protecting workers from heat injury. The optimum length of time to establish a MAWL for a much longer period (a working day for instance) has been investigated extensively. A 40 minute adjustment period was used in the early work by Snook & Ciriello (1974) but more recent studies (Chen, 2003; Mital, 1987; Wu, 1997) have found that between 20-25 minutes is an adequate length of time to establish MAWL. Subsequent to start of this study Wu and Chen (2002) have shown that adjustment period has a significant effect on the MAWL, and MAWL decreases with increasing adjustment periods. An effect of the adjustment period on RPE was also found, with participants increasing their levels of RPE with increasing adjustment periods. However, the study also showed that the effect of the adjustment period on the heart rate was not significant and that the lifting frequency had no significant effect on the percentage decrease in the MAWL from the 20-minute adjustment period. The adjustment period is necessarily governed by the lift frequency with very low frequency lifts (<0.1 lifts.min-1) requiring a much longer time to establish. Part of the problem when examining the literature is the various terminologies used when describing lift frequencies. In the context of this study the 1 lift.min-1 frequency would be considered low frequency but this would not be the case in studies where lifts as infrequent as 0.1 lifts.min-1 and slower have been used. A twenty-minute MAWL stabilisation period for this project was chosen for a number of reasons. If the participants had continued the MAWL for the 40-minute adjustment period followed by Snook and Ciriello (1974) it is likely that in the most extreme conditions that participants would have exceeded the withdrawal criteria and would have had to be removed from the study for health and safety reasons. This would have caused problems for complete data analysis as different participants would have ended the study at different times. Further to this, it was noted in the experimental sessions that the majority of the participants had determined their MAWL about ten minutes into the adjustment period, making few or no adjustment to the weight after this time. Whilst it is possible that had the participants continued with the adjustment period they would have selected lower weights, the consistency of the MAWL across conditions suggests this would not have been the case. A finding of interest from this study is that WBGT seems to be a reliable method of expressing the thermal environment whereas air temperature is not. Throughout the study, there are consistent differences in the dependant variables at similar air temperatures with differing levels of humidity (e.g. hot dry v hot humid) with the dependent variables being significantly more affected in the high humidity environment when compared to the hot dry environment. This would indicate that limiting exposure to non-neutral thermal environments by the establishment of a maximum indoor air temperature would not be sufficient for limiting any increased risk of manual handling in non-neutral thermal environments. It is possible that there was an effect of fatigue over the course of the experiment as participants took part in the study on consecutive days. This effect should however, have been mitigated by counterbalancing of the experimental design. Potential confounding factors in this study are that only males were used so the findings may not be applicable to the female working population. Also, the participants used in this study were young and relatively fit. Whilst age has not been shown to affect responses to the thermal environment, the associated age related changes (e.g. decreasing fitness levels) may. For this reason, findings from this study should be treated with caution when applying them to a typical occupational population. Snook and Ciriello (1974) found that workers were able to compensate for increases in heat stress by reducing their work load and that the amount that the workload was reduced by related

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to heart rate and core temperature. This would not seem to be the case from the results of this study where despite decreases in the MAWL, core temperature and heart rate still increased. The maximum WBGT that Snook and Ciriello investigated however was 27°C. 5.1 HYPOTHESES

The hypotheses that:

• Frequency of lift will have a significant effect on all of the dependent variables.

• Lifting tasks in hot thermal environments will impose a greater physiological load than lifting tasks in thermal neutral environments.

• The MAWL will be lower in hot environments when compared to the

maximum acceptable weight in the thermal neutral environment for a given frequency.

• The MAWL will decrease as the lifting frequency increases regardless of

environmental condition.

• Despite self-regulation of the MAWL, people will not adjust the MAWL enough to account for the increased physiological load imposed by the thermal environment. This physiological load will be manifested in increased core temperature and heart rate.

• The higher WBGT value will impose a greater physiological load than the

lower WBGT value regardless of environment.

• Heart rate will be a good indicator of physiological strain occurring as a result of manual handling in hot environments.

• Core temperature will be a good indicator of physiological strain occurring as a

result of manual handling in hot environments. can all be accepted and the null hypotheses rejected. The stated hypothesis that RPE will be a good indicator of physiological strain occurring as a result of manual handling in hot environments cannot be accepted and, as such the null hypothesis is accepted.

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6 EXPERIMENT 2: ‘COLD’ EXPERIMENT

6.1 DESIGN

A within-subjects repeated measures design was used. Each participant took part in all of the fifteen test conditions. Exposure to each condition was randomised using an unbalanced Latin Square. Each participant was exposed to five environmental conditions and three lifting frequencies (detailed in Tables 20 and 21). Although the effects of cold weather PPE were not examined in depth in this project, two clothing ensembles were worn at 0°C. The exact composition of these clothing ensembles are detailed later in the methods section.

Table 20 Environmental conditions Environment Air temperature (°C) Relative humidity (%) Thermal neutral 15.9 ± 0.72 67.3 ± 6.5 10° C 9.9 ± 0.79 56.2 ± 7.6 5° C 5.0 ± 0.95 44.3 ± 4.4 0° C (Standard Ensemble) 0.45 ± 0.73 59.9 ± 3.6 0° C (Enhanced Ensemble 0.39 ± 0.80 54.8 ± 3

Table 21 Lifting frequencies

Frequency Lifts.min-1

9 seconds 6.7 14 seconds 4.3 60 seconds 1

6.2 PROCEDURES

Ethical approval for this study was granted by Sheffield Hallam University (SHU). All participants were treated in accordance with the Helsinki Declaration 1964 and BASES ethical guidelines. Participants were given oral and written descriptions of the procedures involved (see appendix 2) for the written description) and completed a medical questionnaire before giving written informed consent to continue. Participants with any previous history of musculoskeletal disorders were excluded from the study, as were participants with illness, disorders or diseases known to affect the thermoregulatory system (e.g. thyroid conditions). The participants reported to the environmental chamber at the Centre for Sport and Exercise Science (CSES), Sheffield Hallam University. Height (Holtain stadiometer, Crymych, UK), mass (Balance Scales, Avery, Birmingham, UK) and knuckle height (distance from floor of second metacarpo-phalangeal joint when standing relaxed) were measured. Participants were asked to abstain from alcohol for 24 hours prior to commencement of the study. Skin thermistors (Grant Instruments, Cambs., UK) were fixed to the body with Leukopore tape (3M, USA) according to the Ramanathan 4 point measurement site for estimation of mean weighted skin temperature; at the chest (centre of pectoral region, midpoint between nipple and clavicle), arm (posterior aspect of the upper-arm, at the centre of the belly of the triceps), thigh (anterior aspect, over rectus femoris at midpoint of femur) and shin (anterior aspect of lower-leg, at midpoint of the tibia). These sites correspond to those used by Ramanathan (1964) and allow a weighted formula to be used to calculate mean skin temperature. An additional skin thermistor was taped to the second finger on the dorsal aspect of the first phalanx of one hand. An aural bead thermistor (Grant Instruments, Cambs, UK) was fitted into the ear and secured with tape. The aural bead thermistor was then insulated with cotton wool. A set of industrial ear defenders

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were then donned to provide total insulation of the aural environment from external environmental conditions. All thermistors were connected to a data logger (Squirrel 1021, Grant Instruments, Cambs, UK) so that measurements could be recorded throughout testing. The aural thermistor was left in place for twenty minutes prior to the onset of experimentation to allow the sensor to reach equilibrium. A heart rate monitor was also worn (Polar 610, Polar, UK). Each participant was then provided with either a standard or enhanced clothing ensemble depending on which session they were attending (Table 22 and 23). The clothing ensembles were chosen to replicate as closely as possible the clothing observed to be worn during the site visits. No gloves were worn. The estimated clothing level and associated Clo value was designed to ensure that the participant was comfortable standing in the thermally neutral environment.

Table 22 Standard clothing ensemble and Clo values Clothing Item Clo Underwear (shorts, socks as supplied by participant)

0.05

Working trousers (cotton) 9oz 0.25 T-shirt, thermal 0.09 Fleece jacket 0.4 Safety boots 0.1 Estimated Clo of ensemble 0.89

Table 23 Enhanced clothing ensemble and Clo values

Clothing Item Clo Underwear (shorts, socks as supplied by participant)

0.05

Underpants, Long, Thermal 0.1 T-shirt, thermal 0.09 Working trousers (cotton) 9oz 0.25 Fleece jacket 0.4 Woolly hat 0.1 Safety boots 0.04 Estimated Clo of ensemble 1.03

6.3 ORIENTATION PERIOD

The first two days were designated as an orientation period and took place in the environmental chamber set at 10°C. Six of the participants had recently completed the hot study so these sessions allowed them to practice the test protocol in surroundings which they had previously only associated with hot environments. The six new participants were familiarised with the psychophysical strategy. Prior to entering the environmental chamber for the first time the participants were read a script detailing the test protocol (see appendix 3) and were also familiarised with the Borg 6-20 Rating of Perceived Exertion scale (Borg, 1970). Each session consisted of two twenty-minute work periods separated by ten minutes rest in the warm-down area. 6.4 LIFTING TASK

A shelf in an industrial shelving unit was set at the participant’s knuckle height. A plastic box (60 x 39 x 41 cm) was placed on the floor in front of the shelving unit at a fixed distance from

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it. The box was loaded with weights by the experimenter out of sight of the participant. This weight was concealed in a false bottom so that the participants could not use visual cues to help determine the weight of the box at commencement of the task. The participants then lifted the box from the floor onto the shelf every 14 seconds (4.3 lifts.min-1 (1 every 14 seconds)) in time with a metronome. This constituted one complete lift. On completion of the lift the participant stepped back and an assistant returned the box to its starting position (i.e. participants only lifted the box, no lowering was done by the participant). During the twenty minutes lifting period the participant was encouraged to make adjustments to the box weight by either adding or removing small canvas bags of ball bearings ranging in weight from 1 kg to 10 kg. The aim of this weight adjustment was to arrive at a box weight that the participant found acceptable to lift for a standard eight-hour shift (including breaks etc.) in an industrial setting without the individual becoming unduly fatigued. This procedure is similar to the psychophysical approach adopted by Snook & Ciriello (1974). After approximately 10 minutes rest in the warm-down area the protocol was repeated. 6.5 EXPERIMENTAL SESSIONS

There were 15 sessions conducted at the same time of day (to avoid any circadian rhythm influence) on consecutive days, Monday to Friday. The participants were clothed and equipped as in the orientation sessions and then rested for 20 minutes prior to commencement allowing their aural environment to stabilise. During this period the shelf heights were set and box starting weights were randomised. The participant was told the lift frequency for the session but was not aware of the environmental conditions or the starting box weight. Where two participants were tested simultaneously they were informed that their starting box weights were different thus removing any competitive element from the session. Participants then completed a grip strength test (Grip Strength Dynamometer, TKK 5401, Grip D, Takei Scientific Instruments, Japan) in the warm-down area. The dynamometer was held in the dominant hand in a relaxed fashion at the participant’s side and then gripped as tightly as possible, isometrically contracting the muscles of the fingers and lower arm. Participants were allowed up to three trials and the highest reading was taken. The participants then entered the thermal chamber and all recording equipment was started. They then lifted the box onto the shelf at the prescribed frequency for 35 minutes (an assistant again returned the box to its starting position). Adjustment of the box weight was allowed for the first 20 minutes using the bags of ball bearings provided. After 20 minutes no further adjustments were permitted and the participants continued lifting for a further 15 minutes at that particular box weight. RPE was recorded every five minutes throughout the session and the participants were encouraged to convey this information discreetly so as not to influence the other lifter present. Heart rate readings were also taken manually every five minutes as a back-up procedure. To ensure the health and safety of the participants a second experimenter was always present in the chamber. After 35 minutes the test was stopped, the grip strength test was repeated immediately and then the participants were removed to a warm-down room to de-kit. The final box weight was recorded as the MAWL. 6.6 PARTICIPANTS

Male participants were used to avoid menstrual effects and any confounding variables occurring as a result of differences in anthropometrics between males and females. Some of the participants that took part in the hot studies also took part in the cold studies. Twelve healthy

38

male participants were recruited by general notice and advertisements on the university’s website. Participant characteristics are presented in Table 24.

Table 24 Participant characteristics (means and standard deviation) N Age (y) Stature (m) Mass (kg) Knuckle Height

(m) 12 26 ±5.6 1.77 ±0.06 75.1 ±9.2 0.8 ±0.04 6.7 ENVIRONMENTAL MEASUREMENT

Air temperature was measured using a temperature probe (general purpose thermistor CS-U, Grant Instruments, Cambs, UK), accurate to ±0.2˚C between 0˚C and 70˚C. Relative humidity was measured using a humidity sensor (Rotronic Hygroclip humidity and temperature sensor, Rotronics Instruments UK Ltd., West Sussex, UK), accurate to ±1.5% RH between -40˚C and 85˚C. The probes were positioned behind the participants at approximately 1.1 m distance from the floor. A data logger (Squirrel 1021, Grant Instruments, Cambs., UK) recorded readings every 10 seconds. All data from the loggers were subsequently downloaded into Microsoft Excel (via Squirrelview v 1.03) for analysis. 6.8 WITHDRAWAL CRITERIA

Withdrawal criteria was set at an aural temperature of 35.5°C. Heart rate was monitored simultaneously and consideration given to removing the participant if this exceeded 85% of their age-predicted maximum (based on the other objective and subjective measurements). 6.9 ANALYSIS

A two-factor ANOVA with repeated measures on both factors was conducted on each of the five dependent variables using SPSS v11. α was set at 5%.

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7 RESULTS

7.1 ASSUMPTIONS

The four dependent variables (Heart rate (HRmax), core temperature (Tcmax), RPE and MAWL) were each individually analysed using a two-way, repeated measures ANOVA with 12 participants. The two within subject factors are environment (ENV) and frequency (FREQ) together with the interaction (ENV*FREQ). There are five levels in ENV and three levels in FREQ. The assumptions underlying this type of analysis are that data are normally distributed and display sphericity (homogeneity of covariance). These assumptions are tested in SPSS using a Kolmogorov-Smirnov and Mauchly’s test respectively. 7.2 HEART RATE

The mean end heart rate (average of the last three readings) was calculated for each session. Figure 10. describes the average end heart rate and standard deviation of the participants in each lifting frequency by each environmental condition.

60

80

100

120

140

160

180

Thermal Neutral

10°C 5°C 0°C (Standard clothing)

0°C (Enhanced clothing)

1/60s 1/14s 1/ 9s

Figure 10 Mean end heart rate for three lifting frequencies 7.2.1 Maximum heart rate

All data for HRmax were normally distributed. Mauchly’s test was non-significant for environment and environment*frequency. In order to determine whether starting baseline heart rates were equal for all sessions an ANOVA was run on the baseline heart rate data and ascertained that there was no significant

40

differences (P>0.001). It can therefore be assumed that any differences apparent in heart rate are due to the effects of the environment and/or lifting frequency. The differences in HRmax between each condition and at each lifting frequency and their interactions were investigated. The results of the main analysis for HRmax are detailed in Table 25.

Table 25 Results of ANOVA for maximum heart rate Source Df F Sig (P

value) ENV 4 0.446 Not

Significant FREQ 2 65.644 0.000 PARTICIPANT 11 56.029 0.000 ENV*FREQ 8 1.425 Not

Significant There was a significant main effect for FREQ. The main effect for ENV and the interaction effect were non-significant. The effect of participant was also significant. 7.2.2 Maximum heart rate – post hoc test

Post hoc analysis took the form of pairwise comparisons using Tukey’s tests. The results for frequency are detailed in Table 26.

Table 26 Results of Tukey’s pairwise comparisons for maximum heart rate (frequency)

1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds P<0.01 P<0.01 1 Lift every 14 seconds P<0.01

The effect of frequency on end heart rate was shown to be significantly different between all lifting frequencies. 7.3 CORE TEMPERATURE

The mean end core temperature (average of the final three readings from the experimental session) was calculated. Figure 11 describes the end mean core temperature and standard deviation of the participants in each lifting frequency by each environmental condition.

41

35

36

37

38

Thermal Neutral 10°C 5°C 0°C (Standard clothing)

0°C (Enhanced clothing)

1/60s 1/14s

1/ 9s

Figure 11 Mean end core temperature for three lifting frequencies 7.3.1 Maximum core temperature – ANOVA

In order to determine whether starting core temperatures were equal for sessions an ANOVA was run on the starting core temperature data to ascertain that there were no significant differences (P>0.001). It can therefore be assumed that any differences apparent in core temperature are due to the effects of the environment and/or lifting frequency. All of the data for Tcmax were normally distributed. The results of the main analysis for Tcmax are detailed in Table 27.

Table 27 Results of ANOVA for maximum core temperature Source df F Sig (P

value) ENV 4 15.737 0.000 FREQ 2 50.777 0.000 PARTICIPANT 11 27.004 0.000 ENV*FREQ 8 1.321 Not

Significant There were significant main effects for ENV and FREQ but the interaction effect (ENV*FREQ) was non-significant. The effect of participant was also significant. 7.3.2 Maximum core temperature – post hoc tests

Post hoc analysis took the form of pairwise comparisons using Tukey’s tests. The results for ENV are detailed in Table 28.

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Table 28 Results of Tukey’s pairwise comparisons for maximum core temperature (environment)

10°C 5°C

0°C Standard clothing ensemble

0°C Enhanced clothing ensemble

Thermal neutral Not Significant P<0.05 P<0.01 P<0.01 10°C Not Significant P<0.01 P<0.05

5°C P<0.01 Not Significant

0°C Standard clothing ensemble Not

Significant Core temperature at 0°C with the enhanced clothing ensembles was significantly different from core temperatures at the thermal neutral and 10°C conditions. The end core temperatures at 0°C wearing the standard clothing conditions were significantly different from thermal the thermal neutral 10°C and 5°C environmental conditions. There was also a significant difference between the end core temperature at 5°C and the thermal neutral condition. The results for FREQ are detailed in Table 29.

Table 29 Results of Tukey’s pairwise comparisons for maximum core temperature

(frequency)

1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds P<0.01 P<0.01 1 Lift every 14 seconds P<0.05

The different lifting frequencies were shown to result in significantly different end core temperatures from each other.

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7.4 RATE OF PERCEIVED EXERTION

The mean end rate of perceived exertion values for each session were taken. Figure 12 describes the end average RPE value and standard deviation of the participants in each lifting frequency by each environmental condition.

Figure 12 Mean end RPE for three lifting frequencies

7.4.1 Rate of Perceived Exertion – ANOVA

ed. However, ANOVAS are

Table 30 Results of ANOVA for RPE Source Sig (P

6

20

Thermal Neutral 10°C 5°C 0°C (Standard clothing)

0°C (Enhanced clothing)

1/60s 1/14s

1/ 9s

Six data sets out of 15 were found to be non-normally distributrobust to the violations of this assumption and as there are no two-way non-parametric tests available an ANOVA was used but a higher significance level was accepted (p<0.01). The results of the main analysis for RPE are detailed in Table 30.

Df F value)

ENV 4 1.474 ficant

Not Signi

FREQ 2 10.404 0.001 PARTICIPANT 11 43.776 0.0001ENV*FREQ 8 0.909 Not

Significant

There was a significant main effect for frequency. The main effect, environment and the interaction effect were both non-significant. The effect of participant was also significant.

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7.4.2 Rate of perceived exertion – post hoc tests

Post hoc analysis took the form of pairwise comparisons using Tukey’s tests. The results for

Table 31 Results of Tukey’s pairwise comparisons for rate of perceived exertion

1 Lift s 1 Lift every 9 seconds

FREQ are detailed in table 31.

(frequency) every 14 second

1 Lift every 60 seconds Not Significant P<0.01 1 Lift every 14 seconds P<0.05 (Not Significant)

The one lift every nine seconds frequency was found to be significantly different from the one

.5 MAXIMUM ACCEPTABLE WEIGHT OF LIFT

The mean end MAWL values for each session were taken. Figure12 describes the end average

Figure 12 Mean end MAWL for three lifting frequencies

able 32. shows the mean change percentage in the MAWL by environment and lifting

lift every sixty second frequency. 7

MAWL value and standard deviation of the participants in each lifting frequency by each environmental condition.

0

10

20

30

40

50

Thermal Neutral 10°C 5°C 0°C (Standard clothing)

0°C (Enhanced clothing)

1/60s 1/14s

1/ 9s

Tfrequency from thermal environment.

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Table 32 Mean change percentage in the MAWL by environment and lifting frequency from thermal neutral

Mean Percentage Change in MAWL by Environment and Frequency (%)

1/60s 1/14s 1/ 9s 10°C -4.8 2.3 12.4 5°C -0.6 3.8 5.2 0°C standard clothing -9.0 7.2 0.9

0°C enhanced clothing -2.7 5.9 5.6

The biggest decreased in MAWL was found at 0°C wearing the standard clothing ensemble at the lowest lifting frequency. MAWL was found to increase in all environmental and clothing conditions at the other two frequencies. 7.5.1 Maximum acceptable weight of lift – ANOVA

All of the data for MAWL were normally distributed. The results of the main analysis for MAWL are detailed in Table 33.

Table 33 Results of ANOVA for Maximum acceptable weight of lift

Source Df F Sig (P value)

ENV 4 1.510 Not Significant

FREQ 2 34.362 0.000 PARTICIPANT 11 85.169 0.000 ENV*FREQ 8 1.784 Not

Significant

There was a significant main effect for FREQ. The main effect for ENV and the interaction effect were both non-significant. The effect of participant was also significant. 7.5.2 Maximum acceptable weight of lift – post hoc tests

Post hoc analysis took the form of pairwise comparisons using Tukey’s tests. The results for FREQ are detailed in table 34. Table 34 Results of Tukey’s pairwise comparisons for maximum acceptable weight of

lift (frequency) 1 Lift every 14 seconds 1 Lift every 9 seconds 1 Lift every 60 seconds P<0.01 P<0.01 1 Lift every 14 seconds P<0.05

Frequency was shown to result in a significantly different MAWL when compared to all other frequencies of lift.

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7.6 GRIP DYNANOMETER

-6

-4

-2

0

2

4

6

Thermal Neutral

10°C 5°C 0°C (Standard clothing)

0°C (Enhanced clothing)

1/60s 1/14s

1/ 9s

Figure 13 Mean percentage change in grip strength pre and post lifting task The grip dynamometer readings taken pre and post lifting task were analysed using paired t-tests to investigate effects of environment and lifting frequency on post test strength. The data from one participant were removed as it was outside the normal distribution for that participant group. Only one significant difference was found between pre and post-tests across all environmental conditions and lifting frequencies. Strength was found to significantly decrease after exposure to the 0°C environment whilst wearing the standard clothing ensemble. The effect of environment and frequency of lift on post exposure grip strength was analysed using a two way repeated measures ANOVA. Neither environment nor frequency had a significant effect on the end grip strength measure.

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8 DISCUSSION – COLD EXPERIMENT

This study investigated the effects of cold environments on participants conducting a manual-handling task (box-lifting) using a combination of physiological (objective) and psychophysical (subjective) methods. Many of the discussion points covered in the hot discussion section will be salient to the discussion of the cold experiment. Prior to the analysis of heart rate max, the baseline measures of heart rate were compared to see if there were any significant differences. No significant differences were found so any effect on heart rate could be attributed to the effect of the two independent variables. HRmax was not shown to be affected by the environmental conditions in the cold experiment there was no significant main effect for environment (ENV) in the overall analysis and no significant interaction between ENV and frequency (FREQ). There was, however, a significant main effect for FREQ and post-hoc tests showed that HRmax was significantly lower at 1 lift.min-1 compared to 4.3 lifts.min-1 and 6.7 lifts.min-1 (1 every 9 seconds), and that HRmax at 4.3lifts.min-1 was significantly lower than HRmax at 6.7 lifts.min-1 (1 every 9 seconds). The lack of effect of the cold environment on heart rate was unexpected. Heart rates have been shown to decrease in cold environments in order to compensate for the increase in blood pressure caused by vasoconstriction. It was expected that this would be reflected in the results. It is possible however, that the clothing levels worn and the relatively high ambient conditions used (to reflect temperatures found in cold workplaces) only resulted in very mild vasoconstriction. The standard clothing level chosen was designed to result in a PMV of neutral for a participant stood at rest in the thermal neutral environment. The PMV scale however has been shown to be unreliable in colder environments and it may be that the clothing level used resulted in higher thermal sensations than anticipated. Having said that, the clothing level used was representative of what was found in industry, as were the environmental conditions. One would normally expect heart rate to rise during exercise as a result of demand from working skeletal muscle and this was reflected in the effect of frequency on heart rate. The average heart rate maximum at the low frequency of 1 lift.min-1 (across all environments) was ~80 beats.min-1 which could be considered a resting level for a man in a standing position. This mean was then shown to increase as lifting frequency increased. Despite heart rate being a useful indicator of physiological strain in the hot experiment, in cold environments (>0°C) with a clothing value of 0.9, heart rate does not give any indication of physiological strain occurring. This may be as a result of heart rate being an inappropriate method to evaluate the strain occurring in cold environments, or it may be that heart rate is a reliable indicator and is showing that lifting at these frequencies, at these temperatures with the set clothing ensembles does not impose undue physiological strain. It is likely that if the experiment had investigated the effects of working in frozen food environments that more of an effect would have been demonstrated. Prior to the analysis of the maximum core temperatures, the base line core temperatures were compared to see if there were any differences. No significant differences were found so any effect on core temperature could be attributed to the effect of the two independent variables. There were significant main effects for ENV and FREQ when examining Tcmax. Post hoc tests demonstrated that Tcmax was significantly lower in 0˚C (standard ensemble) compared to the thermally neutral, 5°C and 10°C condition. Three other pairwise comparisons (0˚C (enhanced ensemble) vs TN and 10˚C showed significant decreases and Tcmax was also significantly lower in the 5°C condition when compared to thermal neutral condition. This would indicate that environments below 10˚C may impose increased physiological strain in terms of maintaining

48

core temperature. This may have implications in the food preparation industry where environments <10˚C are commonplace for reasons of food safety. These findings also show that the additional items of clothing (hat and thermal underwear) do offer some protection against decreases in core temperature. As clothing levels in this study were chosen to reflect what was seen to be worn in industry, the appropriate selection of cold weather clothing in cold and frozen environments may need addressing. It is also worth noting that decreases in core temperature were occurring after 40 minutes of exposure to the cold environment and shows that the participants were unable to compensate for the thermal strain. If this decrease continued over the course of a working day, then the fall in core temperature could result in hypothermia. As core temperature has demonstrated an effect of environment and heart rate did not, it is likely that heart rate is insensitive to the physiological strain occurring as a result of manual handling at these frequencies in these environments rather than no physiological strain being present. Core temperature measurement would seem to be more sensitive and as such a more appropriate method of monitoring physiological strain occurring as a result of manual handling in cold environments. Tcmax was significantly lower at 1 lift.min-1 (across all environments) compared to both other lift frequencies. Again, this finding may have implications for the food preparation industry especially for workers involved in less physically demanding tasks (sandwich-filling, cake decorating etc). There was a significant main frequency effect for Ratings of Perceived Exertion (RPE). Tukey's post-hoc test showed the difference to be between -1 lifts.min-1. and 1 lift.min-1. An effect was also found between 6.7 lifts.min-1 (1 every 9 seconds). and 4.3 lifts.min-1 (1 every 14 seconds). but this result was not accepted as significant (P<0.05) because of the violations of the assumptions of using an ANOVA as discussed in the hot study. Only P values ≥ 0.01 were accepted. As was the case in the hot study, the participants appeared to be extremely conservative with their interpretations of perceived exertion despite extensive familiarisation with the RPE scale during the acclimation phase. The other factors affecting RPE including macho effects and the difficulty of rating perceived exertion at the lower lifting frequencies discussed in detail in the hot study would also apply to this study. Further work is probably merited in this area in order to identify the frequency at which RPE becomes invalid as a means of self-regulation of workload. The maximum acceptable weight of lift (MAWL) was the box weight selected after 20 minutes of lifting and represented the amount of weight that a participant would be happy to lift over the course of a normal 8 hour shift. There was a significant main effect for frequency with the MAWL at 1 lift.min-1 being significantly higher than at 6.7 lifts.min-1 (1 every 9 seconds). There was no significant main effect for environment, in fact the range of MAWL values across all environments was only 0.61 kg. When compared to the tables produced by Snook & Ciriello (1991) the MAWL values for the participants in the present study were just below the 50th percentile at 1 lift.min-1 and between the 50th and 75th percentile for the other two frequencies. Both of the mean values for MAWL at 4.3 and 6.7 lifts.min-1 (1 every 9 seconds) were highlighted by Snook & Ciriello (1991) as values that may cause the lifter to exceed the physiological limit of 33% VO2max. The mean values for MAWL were higher (~5 kg) across all environments compared to the results of the hot study. At 1 lift.min-1 the MAWL across all environments was 29.6 kg compared to 22.4 kg in the hot study and there were smaller, but consistent, increases at both of the other lifting frequencies. Within this some participants were lifting up to 40 kg at the lower lifting frequencies. It is suggested that the participants lifted a greater amount in the cold study

49

in order to keep warm by increasing their metabolic activity (this was alluded to by more than one participant). If this practice is commonplace outside of the laboratory setting then this has implications for industry because it suggests that individuals are willing to put themselves at a greater risk of acute musculoskeletal injury in order to maintain thermal comfort. As well as the increased risk of acute musculoskeletal injury, this also has implications for the thermal well being of the individual. If people work sufficiently hard to start sweating, and their work is intermittent, the enhanced cooling effects as result of evaporation will result in the worker cooling more quickly. This could then result in cyclic behaviour where the worker increases weight again to keep warm, sweats more, the core temperature decreasing eventually resulting in either cold strain or injury. This study investigated the immediate physiological effects of manual handling in cold environments. It is possible that there are cumulative effects of working in cold environments that would only become apparent over time. This would be an area for further investigation. When looking at the mean percentage change in the MAWL, across all environments and lifting frequencies, it is interesting to note that the MAWL only decreased at the 1 lift.min-1 frequency. The MAWL actually increased at both of the other frequencies in every condition. It is suggested that this is an effect of the muscles ‘warming up’. At the 1 lift.min-1 frequency the participant was only moving for a very small fraction of the time compared with the more continual use of the muscles used for the lifting task in the higher lifting frequencies. This means that each time the participant completed the 1 lift.min-1 they were effectively doing so for the first time. At the higher lifting frequencies, the muscles would have had time to warm up resulting in less strain being put on the muscles and a higher weight being lifted. The results from the grip dynamometer were surprising. It was expected that there would be a significant decrease in strength after the experiment when compared to strength before exposure and that the end strength would be significantly worse in the colder conditions when compared to the relatively warmer conditions and thermal neutral. It was found that strength did significantly decrease after exposure to the 0°C condition whilst wearing the standard clothing ensemble but in no other condition. The effect of environment and frequency of lift on post grip strength was found to be not significant for all conditions. The fact that there was a significant decrease in strength between the start and end of the exposure in the 0°C condition and not the 0°C with enhanced clothing condition again demonstrates the beneficial effect of increased clothing levels in the cold environment. 0°C with the standard clothing ensemble was the most extreme condition so any effect would be most likely to be seen here. A possible reason for the lack of effect of the cold environment on heart rate was that vasoconstriction had only occurred to a small extent due to the metabolic rate and clothing levels worn in the environment. The mild vasoconstrictive response may also go part way to explaining the lack of effect of exposure to the cold environment on strength. If vasoconstriction is only mild, then the decrease in blood flow to the extremities would also be small. This will result in continued heat input from the blood to the extremities maintaining the temperature of the physiological structures. The boxes that were lifted were plastic. Plastic will result in a relatively low level of heat transfer from the hands to the material. This will reduce any local vasoconstrictive effects and subsequent reductions of manual dexterity that might occur if the box was made of metal for example. Overall, frequency has been shown to have a bigger effect on the dependent variables than the cold environments. It would appear that in cold environments avoiding very high and very low lift frequencies is advisable.

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8.1 HYPOTHESES

The hypotheses that:

1. Frequency of lift will have a significant effect on all of the dependant variables.

2. Core Temperature will be lower in cold environments when compared to Core Temperature in the thermal neutral environment for a given frequency

can be accepted and the null hypothesis rejected. The hypotheses that:

1. The MAWL will be lower in cold environments when compared to the maximum acceptable weight in the thermal neutral environment for a given frequency.

2. Heart rate will be lower in cold environments when compared to heart rate in the

thermal neutral environment for a given frequency.

3. Heart rate will be lower in 0°C with the standard clothing ensemble than in 0°C with the enhanced clothing ensemble for a given frequency.

4. Rate of Perceived Exertion will be lower in cold environments when compared to RPE

in the thermal neutral environment for a given frequency.

5. Rate of Perceived Exertion will be lower in 0°C with the standard clothing ensemble than in 0°C with the enhanced clothing ensemble for a given frequency.

6. Grip strength will decrease in the cold environments when compared to grip strength in

the thermal neutral environments. are rejected and the null hypotheses accepted.

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9 CONCLUSIONS AND RECOMMENDATIONS FOR RISK ASSESSMENT

The hot and cold studies have shown that non-extreme, non-neutral thermal environments affect manual handling. Below are a number of points for consideration when assessing the risk of manual handling in non-neutral thermal environments. However, to set definitive limits based on environmental exposure more work would be needed. There is significant variation between individuals in terms of their physiological responses to manual handling in non-neutral thermal environments. This imposes significant limitations on the ability to generalise guidance on manual handling limits in these conditions to control for the risk of injury. If it is not possible to modify the environmental conditions through environmental controls, for example, and there is perceived to be a risk of undue physiological strain, this could be monitored on an individual basis using heart rate as an indicator in hot environments and core temperature in cold environments. Workers appear to be unable to effectively assess their level of physiological strain from manual handling in non-neutral thermal environments, and may actually overestimate their capabilities. This means that it may be unsafe to allow workers to pace themselves in terms of lifting tasks. Decreasing lifting frequency in hot environments would go some way to reducing the extra physiological strain imposed by hot thermal environments. A suggested frequency limit for hot environments could be one lift every 14 seconds. Alternatively, lifting frequency could be limited by heart rate, although inter-individual variation may make this impractical in a work place, especially in team working situations. The lifting frequency certainly should allow the worker adequate time for rehydration i.e. the opportunity for drinking water. It is possible that a rehydration strategy could be incorporated into guidance or into L23 as a risk reduction strategy to be considered if manual handling in a hot environment is unavoidable. In hot environments, the level of clothing chosen should prevent the build up of metabolic heat (where selection of clothing does not interfere with selection of appropriate PPE to control existing risks). Ideally, the clothing should be layered to allow the worker to add/remove clothing according to their thermal environment and activity level if this level could reasonably be expected to vary during the day. Humidity has been shown to significantly affect physiological strain in hot environments. Therefore any risk assessment based on air temperature alone is not appropriate in hot environments and WBGT seems to be an adequate way of expressing the thermal environment for this purpose. However, any risk assessments should also include the effects of metabolic rate and clothing. It should be noted however, that this study only investigates the effects of non-extreme thermal environments. If people are absent from work for a prolonged period of time, their workload may need to be reduced in non-neutral thermal environments whilst they re-acclimatise. Any risk assessment would need to be reviewed upon their return to work. The current risk filter in L23 is not adequate in filtering the increased risks associated with manual handling in hot environments. Completion of a more detailed risk assessment is advised when manual handling is conducted in hot environments. It is suggested that additional information is included in the assessment checklist included in L23 on how to judge if an environment is hot. Subjective estimation may not be reliable and the monitoring of the thermal environment often requires the use of expensive equipment or specialist knowledge. It is

52

therefore suggested that rather than base the risk assessment on environmental parameters, the risk assessment could be based on the monitoring of heart rate to account for thermal stress (as this was shown to be a reliable indicator of strain whilst manual handling in the heat). This would also take into account individual differences that have been shown to have a significant effect throughout the study. The limit for maximum heart rate for each individual could be based on ISO 9886 ‘Evaluation of thermal stress by physiological measurements’ (this would require the support of an occupational physician however). In cold environments where employees self select the weight of lift or lifting frequency, extra care should be taken to ensure that the amounts lifted are not going to cause injury. It is possible, where inappropriate clothing levels have been chosen, that in order to compensate for the heat loss, excessive weights and/or lifting frequencies may be adopted. This was indicated in this study and may result in an elevated risk of injury if workers are allowed to pace themselves in terms of lifting tasks. The risk filter in L23 however should be sensitive to this behaviour. Frequency of lift had a significant effect on heart rate, RPE and MAWL. Environment did not affect these parameters in the cold study. However, the thermal environment as well as lifting frequency was shown to negatively affect core temperature in the cold environment. This would suggest that the deleterious effects of manual handling in the cold could be mitigated by the selection of appropriate cold weather clothing (where other control mechanisms are not practicable e.g. for food hygiene reasons). It is therefore recommended that for manual handling in the cold the employee has adequate cold weather clothing and the opportunity to re-warm in a warm room at regular intervals. The clothing provided should match the worker’s activity level, and the worker should be able to adjust their clothing level to match the demands of the thermal environment and their activity level. The clothing should prevent excessive heat loss without causing excessive sweating. Overall, frequency has been shown to have a bigger effect on the dependent variables than the cold environments. It would appear that in cold environments avoiding very high and very low lift frequencies is advisable. For manual handling in cold environments at higher lifting frequencies (i.e. where there are no long periods of inactivity), the risk filter in L23 will suffice (if the worker is wearing an appropriate level of clothing). Any clothing selected for work in the cold should also take into account the level of activity that the worker would be expected to undertake during the day to prevent the core temperature dropping excessively or too much sweating occurring during bursts of activity. At lower lifting frequencies (when there are long periods of inactivity), additional risk factors are present in cold environments that are not currently considered by the L23 risk filter. A more detailed risk assessment is therefore advised. Additional guidance to enhance the section of the risk assessment in Appendix 4, Part B of L23 that deals with the thermal environment and appropriate PPE could be provided, pointing the user in the direction of the correct clothing standards for cold weather work, or even give suggested clothing ensembles or examples of clothing ensembles for prevalent environmental conditions in UK industry. Although decreases in strength were not shown to be an issue in this study, it is likely that over the course of a shift, dexterity deficits as a result of cold exposure will be observed. This factor could be incorporated into a risk assessment for manual handling in non-neutral thermal environments. In summary, the risk filter in L23 is probably sufficient to screen additional risks of manual handling in cold environments (above 0°C) at lifting frequencies where there are no prolonged

53

periods of activity e.g. at approximately one lift every 14 seconds. In all other non-neutral thermal environments where manual handling is undertaken it is advised that an additional risk assessment is conducted based on the findings summarized in Table 35. To this end, the assessment checklist in L23, Appendix 4, Section B could be expanded to account for the increased physiological strain placed on the worker as a result of manual handling in non-neutral thermal environments. At present a risk value (low, medium or high) is assigned for manual handling in hot/cold/humid conditions. It is suggested that an additional subset of questions could be added under the working environment section of the checklist where manual handling in non-neutral thermal environments is unavoidable, as some of the risk factors for manual handling in non-neutral thermal environments are already included elsewhere in the assessment check-list. When considering work in non-neutral thermal environments which is self paced, the checklist could be reworded to include the additional manual handling risk factors, identified here (excessive loads/lift frequencies as working strategies). Work rates imposed by a process are already considered as a negative on this checklist. Other factors such as whether adequate time/means of hydration is allowed, whether maximum heart rates are exceeded (if this approach to limiting strain resulting from manual handling in hot environments, or assessing the environment were to be adopted), whether clothing levels are appropriate to both the environment and activity level, acclimatisation status etc., could be included in the subset of the working environment.

Table 35 Suggested approaches to control of manual handling (lifting) tasks in non-neutral thermal environments

Low Frequency High Frequency

Hot Environments

L23 Risk Filter not adequate. Conduct a risk assessment (possibly using heart rate to assess the environment)

L23 Risk Filter not adequate. Conduct a risk assessment (possibly using heart rate to assess the environment)

Cold Environments

L23 Risk Filter not adequate. Conduct a risk assessment (possibly using core temperature to assess the effect of the environment. Examine clothing levels etc.)

Use L23 Risk Filter

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10 FURTHER WORK

The amount of information as to the level of injury occurring in non-neutral thermal environments and the quantification of these environments is very limited. To get a complete picture of the level of risk that manual handling in non-neutral thermal environments poses, environmental information would need to be gathered when investigating RIDDOR reportable events. A review of this information would help clarify the situation. Detailed modifications to L23, taking into account the risk factors identified through this study could be made expanding on the assessment checklist in L23, Appendix 4, Section B. As mentioned in the literature review, the effects of manual handling work in frozen environments have not been investigated. It is likely that this would have a bigger effect on all of the dependent variables than manual handling in cold environments. However, the increase in cold weather PPE required to work in frozen environments may cloud the issue and it may be that people are at risk of heat stress due to inappropriate PPE selection. The potential hobbling effects of cold weather PPE on manual handling tasks may warrant investigation, as it may be that postures adopted for manual handling are significantly altered due to the increased layers of insulation. The methods by which people select cold weather PPE may also need clarifying. The effect of the addition of two items of clothing (thermal underwear and a hat) has been shown to significantly affect core temperature in cold environments in this study and this effect is likely to be enhanced in frozen environments. Recent queries from the general public have illustrated a lack of knowledge in this area. The effects of ‘warming up’ practices on manual handling in the cold could be investigated further with a view to decreasing the number of injuries occurring whilst manual handling in cold and frozen environments. The effects of manual handling in non-neutral thermal environments on females may warrant further investigation as work done to date has only investigated the effects on non-neutral thermal environments on males. RPE has been shown to be a quick, reliable and cheap method of assessing physiological strain occurring in the work place due to manual handling tasks (Asfour et al 1983). However, a number of issues with the RPE scale have been found during the course of this study. RPE has been shown to be an unreliable indicator of physiological strain at lower lifting frequencies so to identify the frequency at which RPE becomes invalid, as a means of self-regulation of workload would be useful if this tool is to be used successfully in the field. The quantification of the effects of RPE in non-neutral thermal environments would also increase its usefulness in the field. This study investigated the immediate effects of manual handling in hot and cold environments on physiological strain. The long-term effects of manual handling in non-neutral thermal environments have not been investigated. An epidemiological study into the effects of working in non-neutral thermal conditions would add to the knowledge base for future guidance. A lot of manual handling tasks take place outside. Wind chill effects were not investigated in this study and are likely to have serious implications for manual handling work. The effects of wind chill on manual handling tasks would be an area for further research. The boxes lifted in this study were made of plastic. Plastic has a relatively low thermal contact coefficient. This means that heat will be transferred slowly from the hands to the material and

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vice versa. The effects in terms of cold injury and decreased dexterity or burns from handling boxes containing materials with high thermal contact coefficients e.g. metal may warrant further investigation.

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ISO 11079:1999 (1999). Evaluation of cold environments-Determination of required clothing insulation (IREQ). International Organisation for Standardisation. ISO 7726:1985 (1985). Thermal environments-Instruments and methods for measuring physical quantities. British Standards Institution: London. ISO 7243:1989 (1989). Hot environments-Estimation of the heat stress on working man, based on the WBGT-index (wet bulb globe temperature). British Standards Institution: London. ISO 7933:1989 (1989). Hot environments-Analytical determination and interpretation of thermal stress using calculation of required sweat rate. International Organisation for Standardisation. ISO 9886 (2000). Evaluation of thermal strain by physiological measurements. International Organisation for Standardisation. Jorgensen, M.J., Davis, K.G., Kirking, B.C., Lewis, K.E.K., & Marras, W.S. (1999). Significance of biomechanical and physiological variables during the determination of maximum acceptable weight of lift. Ergonomics, 42, (9), 1216-1232. Keatisuwan, W., Ohnaka, T., Tochihara, Y. (1996). Physiological responses of men and women during exercise in hot environments with equivalent WBGT. Appl Human Sci. Nov;15(6):249-58 Kamon, E., & Belding, H.S. (1971). The physiological cost of carrying loads in temperate and hot environments. Human Factors, 13, (2), 153 - 161. Karwowski, W. (1996). Maximum safe weight of a lift: A new paradigm for setting design limits in manual lifting tasks based on the psychophysical approach. Proceedings of the Human Factors and Ergonomics Society (Santa Monica, CA: Human Factors & Ergonomics Society), 614-618. Kellett, E-M., Weller, A.S., & Withey, W.R. (2003). Heat strain during a work-in-heat test is greater in a warm-humid than in a hot-dry environment of equal wet bulb globe temperature in men. Proceedings of the Physiological Society (Unversity College, London), Vol. 547.P. Kramer, K., & Schulze, W. (1948). Cold dilatation in skin vessels. Pflugers Arch, 250, 141. Legg, S. J., Myles, W. S. (1981). Maximum acceptable repetitive lifting work load for an 8 hour work day using psychophysical and subjective rating methods. Ergonomics. 24:907-916 Lewis, T. (1930). Observations upon the reactions of the vessels of the human skin to cold. Heart, 15, 177. Lindinger, M.I. (1999). Exercise in the heat: Thermoregulatory limitations to performance in humans and horses. Canadian Journal of Applied Physiology, 24, (2), 152-163. Maw, G.J., Boutcher, S.H., Taylor, N.A. (1993). Ratings of perceived exertion and affect in hot and cool environments. Eur J Appl Physiol Occup Physiol. 67(2):174-9 Marieb, E.N. (1998). Human anatomy & physiology (4th ed.). Addison-Wesley: Menlo Park, CA.

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Mital, A., Nicholson, A.S., & Ayoub, M.M. (1993). A guide to manual materials handling. London:Taylor & Francis. Mital, A. (1987). Maximum Weights of Asymmetrical Loads Acceptable to Industrial Workers for Symmetrical Manual Lifting. American Industrial Hygiene Association Journal, 48, (6), 539-544. Mital, A., Manivasagan, I. (1983) Subjective estimates of one handed carrying tasks. Applied Ergonomics 14:265-269 Morton, R., & Provins, K.A. (1960). Finger numbness after acute local exposure to cold. Journal of Applied Physiology, 15, (1), 149-154. Muir, I.H., Bishop, P.A., Lomax, R.G., & Green, J.M. (2001). Prediction of rectal temperature from ear canal temperature. Ergonomics, 44 (11), 962-972. NIOSH (1981). Work practices guide for manual lifting. US Department of Health and Human Services. National Institute for Occupational Safety & Health: Cincinnati, OH. Nielsen, B., & Nybo, L. (2003). Cerebral Changes During Exercise in the Heat. Sports Medicine, 33 (1), 1 - 11. Noakes, T.D. (2000). Exercise and the cold. Ergonomics, 43, (10),. 1461-1479. Oksa, J., Ducharme, M.B., Rintamaki, H. (2002). Combined effect of repetitive work and cold on muscle function and fatigue. J Appl Physiol. Jan;92(1):354-61. Parsons, K.C. (1993). Human thermal environments. The effects of hot, moderate and cold environments on human health, comfort and performance. Taylor & Francis: London. Piedrahita, H., Punnett, L., Shahnavaz, H. (2004). Musculoskeletal symptoms in cold exposed and non-cold exposed workers. International Journal of industrial Ergonomics. 34(4):271-278. Powers, S.K., & Howley, E.T. (1997). Exercise physiology. Theory & application to fitness & performance (3rd ed.). Boston, MA: McGraw-Hill. Pr EN 1005. (2003). Safety of Machinery-Human Physical Performance. (draft publication). Raman, E., and Roberts, M. 1989. Heat savings from alterations of venous distribution versus counter current heat exchange in extremities. In: Mercer JB (ed) Thermal Physiology. Elsevier Science Publishers B.V 167-173 Sato, F., Owen, M., Matthes, R., Sato, K., & Gisolfi, C.V. (1990). Functional and morphological changes in the eccrine sweat gland with heat acclimation. Journal of Applied Physiology, 69, (1), 232 - 236. Shephard, R.J. (1997). Aging, Physical Activity & Health. Champaign, IL: Human Kinetics. Snook, S.H. (1978). The design of manual handling tasks. Ergonomics, 21, 963-985. Snook, S.H., & Ciriello, V.M. (1974). The effects of heat stress on manual handling tasks.

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American Industrial Hygiene Association Journal, 35, 681 - 685. Snook, S.H., & Ciriello, V.M. (1991). The design of manual handling tasks: revised tables of maximum acceptable weights and forces. Ergonomics, 34, (9), 1197-1213. Snook, S.H., & Irvine, C.H. (1967). Maximum acceptable weight of lift. American Industrial Hygiene Association Journal, 28, 322-329. Snook, S.H., & Irvine, C.H. (1969). Psychophysical studies of physiological fatigue criteria. Human Factors, 11, (3), 291-300. Stevens, S.S. (1958). Problems and methods of psychophysics. Psychological Bulletin, 55, 177-196. Sunderlin, G., Hagberg, M. (1992). Effects of exposure draughts on myoelectric activity in shoulder muscles. Journal of Electromyographic Kinesiology. 2 :36-41 Tayyari, F., Emanuel, J.T., & Qureshi, A. (1999). Physiological costs of a lifting task. Advances in Occupational Ergonomics & Safety, (Vol. 3), 117-124. Teichner, W.H. (1957). Manual dexterity in the cold. Journal of Applied Physiology, 11, (3), 333-338. Vangaard, L. (1975). Physiological reactions to wet cold. Aviation, Space & Environmental Medicine, 46, (2), 33-36. Wagner, J.A., Robinson, S., & Marino, R.P. (1974). Age and temperature regulation of humans in neutral and cold environments. Journal of Applied Physiology, 37, (4), 562-565. Waters, T.R., Putz-Anderson, V., Garg, A., & Fine, L.J. (1993). Revised NIOSH equation for the design and evaluation of manual lifting tasks. Ergonomics, 36, (7), 749 - 776. Westman, J. (1999). Concerning the application of the new Swedish provisions "work in intense heat". International Conference on Evaluation and Control of Warm Thermal Working Conditions (BIOMED "Heat Stress" Research Project), June 14-15, 1999, Barcelona. HSL: UK. Whittaker, D.K. 1972. Cryosurgery of the Oral Mucosa: A Study of the Mechanisms of Tissue Damage. The Dental Practitioner and Dental Record. 22(12):445-451. World Medical Association Declaration of Helsinki. Ethical Principles for Medical Research Involving Human Subjects (1964). http://www.wma.net/e/policy/b3.htm (accessed 6/9/2004) Wu, S-P. (1997). Maximum Acceptable Weight of Lift by Chinese Experienced Male Manual Handlers. Applied Ergonomics, 28, (4), 237 - 244. Wu, S., P., Chen, J.,P. (2003). Effects of the adjustment period on psychophysically determined maximum acceptable weight of lift and the physiological cost. International Journal of Industrial Ergonomics 3:287-294 Young, A. J., Castellani, J. W. (2001). Exertion-induced fatigue and thermoregulation in the cold. Comparative Biochemistry and Physiology – Part A: Molecular and Integrative Physiology. 128(4):769-776

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12 GLOSSARY

ANOVA: Analysis of variance a statistical test that estimates the significance between sets of Means Anthropometrics: the study and recording of the physical dimensions, proportions and composition of the human body. CIVD: Cold Induced Vasodilation ‘a cyclic vasodilation resulting from the cyclic loss of the responsiveness of the vascular smooth muscle to Noradrenalin that occurs with the lowering of local temperature’ (Blatteis 1998) Clo: an estimation of clothing insulation as if the clothing was spread over the whole body. Confounding Factors: An uncontrolled factor which obscures the effect sought usually in a systematic way. Core Temperature: Approximation of the temperature of the internal organs Dependant Variables: Variable which is assumed to be directly affected by changes in the independent variable. HR change: The change in heart rate from the baseline measurement HR max: The peak heart rate reached L23: The Manual handling regulations (updated in 2004) MAWL: Maximum acceptable weight of lift. The weight a participant feels they would be able to lift at a set frequency for an eight hour shift Mean Skin Temperature: The mean value of the skin over the whole body Normally Distributed: Variation or spread of data characterised by a bell shape symmetry about its mid point. PMV: Predicted Mean Vote. A thermal comfort index that predicts the mean thermal comfort group of a population when the air temperature, radiant temperature, air velocity and humidity of the environment and also individual factors such as the type of work and clothing worn are taken into account. PPD: Percentage of People Dissatisfied. A thermal comfort index that predicts the percentage of the population likely to be dissatisfied with their thermal environment when the air temperature, radiant temperature, air velocity and humidity of the environment and also individual factors such as the type of work and clothing worn are taken into account. Repeated Measures: Each participant takes part in all conditions of the independent variables RPE: Rating of Perceived Exertion. A subjective rating of how hard a participant thinks they are working. Tc Change: Change in core temperature from the baseline measurement Tc max: Peak core temperature measurement VO2max: the maximum amount of oxygen in ml that can be used in one minute per kilogram of body weight. Those who are fitter have higher VO2 max values and can exercise more intensely than those who are not 6.7 lifts.min-1: One lift every 9 seconds 4.3 lifts.min-1: One lift every 14 seconds1 lift.min-1: One lift a minute

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APPENDIX 1 SUMMARY OF CURRENT THERMAL STANDARDS

International standards exist for the monitoring of environmental and personal variables (i.e. air temperature, radiant temperature, air velocity, humidity, clothing and activity levels) and their effect on humans. Only thermal environment standards directly relevant to this review shall be described. Other thermal environment standards have been excluded as they are outside of the scope of this study. BS EN 27726: ‘Thermal Environments- Instruments and Method for Measuring Physical Quantities’ BS EN 27726 (1985) was produced with a view to standardising the methodology and instrumentation used for measuring the physical quantities present in thermal environments. The standard identifies four basic physical quantities that can affect the environment. These are air temperature, mean radiant temperature, absolute air humidity and air velocity. Indices are available that utilize these measurements, often in combination with personal parameters (i.e. clothing and activity levels). In industry, the indices most commonly referred of these indexes are the wet bulb globe temperature (WBGT) and predicted mean vote (PMV) and percentage of people dissatisfied (PPD). BS EN 27243: 1994 ‘Hot environments. Estimation of the heat stress on working man, based on the WBGT-index (wet bulb globe temperature)’ BS EN 27243 provides an estimation of heat stress based on the WBGT index. The WBGT index uses a combination of two derived parameters (natural wet bulb temperature and globe temperature (air temperature is assumed to equal globe temperature in indoor environments without significant radiant heat)) and, in conditions with a solar load (radiation from the sun), air temperature (ISO, 1989. ISO 7243 uses an assessment of the individual's metabolic rate (usually from a reference table based on types of activity) and sets upper limits of WBGT above which heat stress injury could reasonably be expected to occur). Environments with the same WBGT may vary considerably (e.g. a hot-dry or warm-humid environment may have the same WBGT value) but it is assumed that the different conditions will impose the same thermal load on a human subject if the WBGT remains constant. Use of the index is reported to be inappropriate for environments exceeding 33˚ C WBGT (Westman, 1999). ISO 9886:2000 ‘Evaluation of Thermal Strain by Physiological Measurement’ ISO 29886 (2000) provides methods of evaluating human thermal strain by using physiological measurements. The standard specifies methods of measuring and interpreting many of the physiological markers that are of interest when considering the individual's response to a hot or cold environment. The measurement of core temperature and its interpretation is detailed for the most widely used methodologies including measurement of rectal, oral, aural and gastro-intestinal temperature. Local and mean skin temperature measurement methods are also detailed together with guidance on factors that may affect these readings. Finally, prediction of heat strain based on heart rate and indicators of physiological strain based on sweat rate are outlined. The standard states that the increase in heart rate due to thermal stress is approximately 33 beats.min-1 per 1˚ C rise in core temperature. Using a core temperature cut-off of 39˚ C the standard recommends that heart rate should not rise more than 60 beats.min-1 from a baseline in a thermal neutral environment. With regard to sweat rate, ISO 29886 (2000) recommends that total body water loss equal to 5% of body mass should be regarded as a limit value. ISO 7933: ‘Hot environments – Estimation of heat stress on working man, based on the WBGT index (wet bulb globe temperature) Another widely used method of predicting heat strain from physiological parameters is detailed in ISO 27933 (1989). This standard describes a method of calculating required sweat rate in

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order to maintain thermal equilibrium in a hot environment. It uses measurements of the four environmental parameters together with an assessment of metabolic heat production and clothing insulation levels. ISO 27730: ‘Moderate thermal environments – determination of the PMV and PPD indices and specification of the conditions for thermal comfort’. This standard considers whole body thermal sensation and local thermal discomfort caused by draughts. It is based on work by Fanger (1970) and uses the predicted mean vote (PMV) and predicted percentage of people dissatisfied (PPD) indices. It uses the six basic parameters and the heat balance equation for the human body to predict a person’s thermal sensation in a given environment and the percentage of people likely to be dissatisfied with that thermal environment. It is used in situations where thermal comfort is likely to be an issue. It is not used in the assessment of more extreme thermal environments. ISO 11079: ‘Evaluation of cold environments: determination of required clothing insulation’. This standard, entitled "Evaluation of cold environments-Determination of required clothing insulation (IREQ)", provides guidance on levels of insulation from various clothing ensembles and their ability to maintain thermal balance in cold environments. ISO 11079 also describes the calculation of wind chill index (WCI). This is an important factor mainly in outdoor environments but can be applied to indoor environments where there is an appreciable level of air movement. BS 27915: ‘Ergonomics of the Thermal Environment- Guide to Design and Evaluation of Working Practices for Cold Indoor Environments’. This British Standard provides guidance on how to evaluate cold stress or discomfort in cold indoor environments. The document describes the risks of cold environments and outlines how these risks may be minimised. ISO 8996 ‘Determination of Metabolic Heat Production’ The direct measurement of oxygen consumption provides the most accurate estimate of metabolic heat production, however it is difficult to measure this in the field. This standard provides information and tables on different work activities and the estimated metabolic rate whilst carrying out these tasks. The reader is directed to ISO 11399: Ergonomics of the thermal environment – principals and application of relevant international standards at this point for further information on available thermal standards.

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APPENDIX 2 MANUAL HANDLING IN THERMAL ENVIRONMENTS: SITE VISIT SUMMARIES

Bakeries Initial site visits were conducted in five bakeries to identify tasks involving manual handling performed in non -neutral thermal environments. The following areas were identified as areas where manual handling could be expected to be undertaken in the bakery industry. • Pastry making • Doughnut frying • Weighing out and mixing ingredients • Unpacking frozen meat • Filling brew vats • Loading oven trolleys • Oven tray handling • Despatch room activities • Shops Task: Pastry making

Type of load Pastry is layered with fat, then cut to length and rolled

onto nylon ‘pins’. These are then manually lifted onto trolleys and wheeled to the rolling and cutting machinery, and lifted into place

Weight of load

25kg per full pin

Lift repetition

3-4 pins handled per minute

Task duration

8 hour shift. Two shifts are operated: 0500-1300 and 1300-2100. Workers remain in one process area and rotate jobs within it

Lifting height Pins are lifted from a 940 mm high conveyor onto racks

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which are at 460 mm, 800 mm, and 1120 mm high on the trolleys

Environmental control

None. Thermal conditions in the factory are affected by seasonal changes

Subjective Estimate of Environmental conditions

Slightly warm with moderate humidity. No sources of strong radiant heat. Some localised air movement from dust extraction machinery

PPE

Bakers overalls, helmet, hairnet, ear defenders, facemasks in some areas, footwear was bakers shoes (plimsolls), a plastic cover was placed over these for certain areas.

Notes Flour dust and seasoning in the air was deemed to make the environment in the pastry preparation areas unsuitable for measurement Controlling the temperature of the food was considered to be more important than the temperature of the environment. Workers compensated for changes in temperature by varying the amount of clothing that they wore under their PPE

Task: Doughnut frying Type of load Racks of doughnuts are taken from a trolley, fried, and

then placed on another trolley for cooling and despatch to the packing area

Weight of load

A full rack of uncooked doughnuts weighs 3.2kg

Lift repetition

A rack is handled (lifted in or out of the fryer) every 45 sec

Task duration

8 hour shift with a break every two hours

Lifting height

Trays of doughnuts are removed from trolleys stacked in height from ankle height to above shoulder height and placed in the fryer at waist height

Environmental control

None

PPE A Baker’s jacket was worn over own clothes Subjective Estimate of Environmental conditions

Hot and humid in fryer area with little air movement

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Task: Weighing out and mixing ingredients

Description of load Sacks of dry ingredients such as flour, rusk, and spices

are weighed out into plastic tubs for mixing into dough and pastry

Weight of load

Sacks weigh 20 - 25 kg. Trays of dry mix weigh 20 kg

Lift repetition

Whilst weighing out a pallet full of tubs of dry mix the operator will lift and carry a sack every minute. Tubs are picked up and carried every 5 minutes. We were informed that approximately 60 -70 batches of mix were weighed out per shift.

Task duration

8 hour shift.

Lifting height

Sacks are taken from pallets where they can be stored up to a height of 1540mm high. The sacks are then poured into trays at knee and waist height

Environmental control

None. We were informed that this area does not show great seasonal variation in temperature

Subjective Estimate of Environmental conditions

Neutral. There was some air movement from a dust extraction hood located above the weighing scales. This area was cooler than the pastry room described previously

PPE

Overalls, helmet, hairnet, plimsolls.

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Task: Unpacking frozen meat

Description of load Blocks of frozen pork packed in cardboard

Weight of load

20kg

Lift repetition

Variable

Task duration 8 hour shift

Lifting height

Blocks are lifted from a minimum of ankle height to waist height, and up to shoulder height where trays are stacked for defrosting

Environmental control

The factory has a heating system but no cooling facility. Some employees find that the environment can become chilly. A simple wall mounted thermometer displayed a temperature of 12.5°C.

Subjective Estimate of Environmental conditions

The areas felt slightly cool and humid

PPE

Bakers overalls, hairnet, earplugs, Wellington boots

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Task: Filling brew vats

Type of load Plastic sacks and tubs of prepared vegetables are tipped

into cookers to make pie filling (brew)

Weight of load

20-25 kg

Lift repetition

Every 30 minutes

Task duration

Eight hour shifts. Brew room workers only work in this area of the factory

Lifting height

Tubs and sacks have to be lifted to between waist and chest height to be emptied into the brew vats

Environmental control

None

Subjective Estimate of Environmental conditions

Slightly warm, with high humidity from wet surfaces and steam from the brew vats

PPE

Overalls, apron, hairnet, Wellington boots

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Task: Loading oven trolleys

Description of load Trays of unbaked pies are lifted into trolleys ready for

freezing or baking

Weight of load

13.5 kg

Lift repetition

One lift every 25-30 sec

Task duration

Operators work an eight-hour shift, with some task rotation within the process area

Lifting height

Trays are lifted from just above waist height to between ankle and head height

Environmental control

None

Subjective Estimate of Environmental conditions

Neutral

PPE

Bakers overalls, plastic apron, hairnet, plimsolls

71

Task: Oven tray handling

Description of load Trays of baked rolls, pastries, and croissants

Weight of load

<10 kg

Lift repetition

20 sec on one oven, 6-7 sec on other ovens

Task duration 8 hour shift with breaks

Lifting height

From waist height to ankle height up to above shoulder height

Environmental control

Cooling fans installed in some areas, no other environmental control

Subjective Estimate of Environmental conditions

Warm to very warm. Some hot air movement from the ovens

PPE

White coat, hairnet, oven mitts, forearm protectors, own footwear

Notes Operators at one workstation observed were exposed to heat from an oven vent that was kept open

72

Task: Despatch room activities Type of load Plastic trays of a wide variety of bakery goods are

loaded and unloaded from trolleys for despatch to stores

Weight of load

Variable, depending on weight and quantity of goods handled

Lift repetition

Work is conducted at a moderately brisk pace

Task duration

8 hour shift with breaks

Lifting height

Trays are handled from ankle height to above shoulder height

Environmental control

Thermostat to maintain 2°C environment

Subjective Estimate of Environmental conditions

Cold, with noticeable air movement

PPE

Thermal PPE is provided

Summary Many of the tasks observed in bakeries involved repetitive manual lifting.

Environmental Measurement Environmental measures were taken and recorded every 1 minute (or 15 minutes if the

equipment was left over night) using a QuesTemp 36°. The parameters measured were air

temperature, web bulb temperature, shielded air temperature and globe temperature. Three

arrays measuring the four parameters detailed previously, were placed at ankle, abdomen and

head height as per the specification in ISO7933. The equipment was left in place for a period of

four hours. Four locations at which repetitive lifting tasks were undertaken were chosen. These

were the doughnut fryer, the chilled room, the proving oven and the bakery shop.

73

Position 1. Doughnut Frying

Environmental Conditions - Doughnut Frying (Head Height)

20

25

30

35

40

11:55

AM

12:03

PM

12:11

PM

12:19

PM

12:27

PM

12:35

PM

12:43

PM

12:51

PM

12:59

PM

1:07 P

M

1:15 P

M

1:23 P

M

1:31 P

M

1:39 P

M

1:47 P

M

1:55 P

M

2:03 P

M

2:11 P

M

2:19 P

M

2:27 P

M

2:35 P

M

2:43 P

M

2:51 P

M

2:59 P

M

3:07 P

M

3:15 P

M

3:23 P

M

3:31 P

M

3:39 P

M

3:47 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Environmental Conditions - Doughnut Frying (Abdomen Height)

20

22

24

26

28

30

32

34

11:55

AM

12:02

PM

12:09

PM

12:16

PM

12:23

PM

12:30

PM

12:37

PM

12:44

PM

12:51

PM

12:58

PM

1:05 P

M

1:12 P

M

1:19 P

M

1:26 P

M

1:33 P

M

1:40 P

M

1:47 P

M

1:54 P

M

2:01 P

M

2:08 P

M

2:15 P

M

2:22 P

M

2:29 P

M

2:36 P

M

2:43 P

M

2:50 P

M

2:57 P

M

3:04 P

M

3:11 P

M

3:18 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

74

Environmental Conditions - Doughnut Frying (Ankle Height)

20

25

30

35

40

45

11:55

AM

12:03

PM

12:11

PM

12:19

PM

12:27

PM

12:35

PM

12:43

PM

12:51

PM

12:59

PM

1:07 P

M

1:15 P

M

1:23 P

M

1:31 P

M

1:39 P

M

1:47 P

M

1:55 P

M

2:03 P

M

2:11 P

M

2:19 P

M

2:27 P

M

2:35 P

M

2:43 P

M

2:51 P

M

2:59 P

M

3:07 P

M

3:15 P

M

3:23 P

M

3:31 P

M

3:39 P

M

3:47 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Doughnut Frying

Sensor Height Value Wet Bulb

(°C)

Dry Bulb

(°C)

Globe

(°C)

RELATIVE HUMIDITY (%)

Min 21.1 29.6 32.3 29.0

Max 22.8 32.5 35.0 41.0 Head

Average 22.0 31.3 33.8 31.3

Min 20.6 29.3 30.8 30.0

Max 22.5 32.3 34.4 46.0 Abdomen

Average 21.7 31.2 33.3 33.2

Min 19.9 28.0 30.3 35.0

Max 21.5 30.4 32.2 46.0 Ankle

Average 20.7 29.6 31.5 36.9

75

Environ )mental Conditions - Chiller Room (Head Height

40

50

60

70

80

90

100

110

12:06

PM

12:14

PM

12:22

PM

12:30

PM

12:38

PM

12:46

PM

12:54

PM

1:02 P

M

1:10 P

M

1:18 P

M

1:26 P

M

1:34 P

M

1:42 P

M

1:50 P

M

1:58 P

M

2:06 P

M

2:14 P

M

2:22 P

M

2:30 P

M

2:38 P

M

2:46 P

M

2:54 P

M

3:02 P

M

3:10 P

M

3:18 P

M

3:26 P

M

3:34 P

M

3:42 P

M

3:50 P

M

3:58 P

M

Time

Rel

ativ

e H

umid

ity (%

)

Relative Humidity

Position 2. Chilled Room

Environmental Condition - Chiller Room (Head Height)

0

20

40

60

80

100

120

12:06

PM

12:14

PM

12:22

PM

12:30

PM

12:38

PM

12:46

PM

12:54

PM

1:02 P

M

1:10 P

M

1:18 P

M

1:26 P

M

1:34 P

M

1:42 P

M

1:50 P

M

1:58 P

M

2:06 P

M

2:14 P

M

2:22 P

M

2:30 P

M

2:38 P

M

2:46 P

M

2:54 P

M

3:02 P

M

3:10 P

M

3:18 P

M

3:26 P

M

3:34 P

M

3:42 P

M

3:50 P

M

3:58 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGobeRelative Humidity

76

Environmental Conditions - Chiller Room (Head Height)

0

2

4

6

8

10

12

12:06

PM

12:13

PM

12:20

PM

12:27

PM

12:34

PM

12:41

PM

12:48

PM

12:55

PM

1:02 P

M

1:09 P

M

1:16 P

M

1:23 P

M

1:30 P

M

1:37 P

M

1:44 P

M

1:51 P

M

1:58 P

M

2:05 P

M

2:12 P

M

2:19 P

M

2:26 P

M

2:33 P

M

2:40 P

M

2:47 P

M

2:54 P

M

3:01 P

M

3:08 P

M

3:15 P

M

3:22 P

M

3:29 P

M

3:36 P

M

3:43 P

M

3:50 P

M

3:57 P

M

Time

Tem

pera

ture

(°C

)

Wet BulbDry BulbGlobe

Environmental Conditions - Chiller Room (Abdomen Height)

2.5

3.5

4.5

5.5

6.5

7.5

8.5

12:06

PM

12:13

PM

12:20

PM

12:27

PM

12:34

PM

12:41

PM

12:48

PM

12:55

PM

1:02 P

M

1:09 P

M

1:16 P

M

1:23 P

M

1:30 P

M

1:37 P

M

1:44 P

M

1:51 P

M

1:58 P

M

2:05 P

M

2:12 P

M

2:19 P

M

2:26 P

M

2:33 P

M

2:40 P

M

2:47 P

M

2:54 P

M

3:01 P

M

3:08 P

M

3:15 P

M

3:22 P

M

3:29 P

M

3:36 P

M

3:43 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobe

77

Environmental Conditions - Chiller Room (Abdomen Height)

72

77

82

87

92

97

102

12:06

PM

12:12

PM

12:18

PM

12:24

PM

12:30

PM

12:36

PM

12:42

PM

12:48

PM

12:54

PM

1:00 P

M

1:06 P

M

1:12 P

M

1:18 P

M

1:24 P

M

1:30 P

M

1:36 P

M

1:42 P

M

1:48 P

M

1:54 P

M

2:00 P

M

2:06 P

M

2:12 P

M

2:18 P

M

2:24 P

M

2:30 P

M

2:36 P

M

2:42 P

M

2:48 P

M

2:54 P

M

3:00 P

M

3:06 P

M

3:12 P

M

Time

Rel

ativ

e H

umid

ity (%

)

Relative Humidity

Environmental Conditions - Chiller Room (Ankle Height)

0

20

40

60

80

100

120

12:06

PM

12:13

PM

12:20

PM

12:27

PM

12:34

PM

12:41

PM

12:48

PM

12:55

PM

1:02 P

M

1:09 P

M

1:16 P

M

1:23 P

M

1:30 P

M

1:37 P

M

1:44 P

M

1:51 P

M

1:58 P

M

2:05 P

M

2:12 P

M

2:19 P

M

2:26 P

M

2:33 P

M

2:40 P

M

2:47 P

M

2:54 P

M

3:01 P

M

3:08 P

M

3:15 P

M

3:22 P

M

3:29 P

M

3:36 P

M

3:43 P

M

3:50 P

M

3:57 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet Bulb BulbDry Bulb BulbGlobeRelative Humidity

78

Environmental Conditions - Chiller Room (Ankle Height)

65

70

75

80

85

90

95

100

105

12:06

PM

12:13

PM

12:20

PM

12:27

PM

12:34

PM

12:41

PM

12:48

PM

12:55

PM

1:02 P

M

1:09 P

M

1:16 P

M

1:23 P

M

1:30 P

M

1:37 P

M

1:44 P

M

1:51 P

M

1:58 P

M

2:05 P

M

2:12 P

M

2:19 P

M

2:26 P

M

2:33 P

M

2:40 P

M

2:47 P

M

2:54 P

M

3:01 P

M

3:08 P

M

3:15 P

M

3:22 P

M

3:29 P

M

3:36 P

M

3:43 P

M

Time

Rel

ativ

e H

umid

ity (%

)

Relative Humidity

Environmental Conditions - Chiller Room ( Ankle Height)

3

4

5

6

7

8

9

12:06

PM

12:13

PM

12:20

PM

12:27

PM

12:34

PM

12:41

PM

12:48

PM

12:55

PM

1:02 P

M

1:09 P

M

1:16 P

M

1:23 P

M

1:30 P

M

1:37 P

M

1:44 P

M

1:51 P

M

1:58 P

M

2:05 P

M

2:12 P

M

2:19 P

M

2:26 P

M

2:33 P

M

2:40 P

M

2:47 P

M

2:54 P

M

3:01 P

M

3:08 P

M

3:15 P

M

3:22 P

M

3:29 P

M

3:36 P

M

3:43 P

M

Time

Tem

pera

ture

(°C

)

Wet Bulb BulbDry Bulb BulbGlobe

79

Chiller Room

SENSOR HEIGHT VALUE

WET BULB DRY BULB GLOBE RELATIVE H )

(°C) (°C) (°C) UMIDITY (%

Min 2.5 3.5 4.0 47.0

Max 10.7 100.7.4 8.4 0 Head

Average

4.4 5.2 5.6 87.2

Min 2.7 3.8 4.1 39.0

Max 7.7 12.0 13.1 100.0 Abdomen

Average 4.7 5.6 5.7 86.4

Min 3.4 4.7 5.3 43.0

Max 7.9 12.0 12.2 100.0 Ankle

Average 5.2 6.2 6.6 82.2

80

Position 3. Proving Oven

Environmental Conditions - Proving Oven (Head Height)

20

25

30

35

40

45

50

55

11:33

AM

11:40

AM

11:47

AM

11:54

AM

12:01

PM12

:08 PM

12:15

PM12

:22 PM

12:29

PM12

:36 PM

12:43

PM12

:50 PM

12:57

PM1:0

4 PM

1:11 P

M1:1

8 PM

1:25 P

M1:3

2 PM

1:39 P

M1:4

6 PM

1:53 P

M2:0

0 PM

2:07 P

M2:1

4 PM

2:21 P

M2:2

8 PM

2:35 P

M2:4

2 PM

2:49 P

M2:5

6 PM

3:03 P

M3:1

0 PM

3:17 P

M3:2

4 PM

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Environmental Conditions - Proving Oven (Abdomen Height)

20

25

30

35

40

45

50

55

60

11:33

AM

11:40

AM

11:47

AM

11:54

AM

12:01

PM

12:08

PM

12:15

PM

12:22

PM

12:29

PM

12:36

PM

12:43

PM

12:50

PM

12:57

PM

1:04 P

M

1:11 P

M

1:18 P

M

1:25 P

M

1:32 P

M

1:39 P

M

1:46 P

M

1:53 P

M

2:00 P

M

2:07 P

M

2:14 P

M

2:21 P

M

2:28 P

M

2:35 P

M

2:42 P

M

2:49 P

M

2:56 P

M

3:03 P

M

3:10 P

M

3:17 P

M

3:24 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

81

Environmental Conditions - Proving Oven (Ankle Height)

18

23

28

33

38

43

48

11:33

AM

11:40

AM

11:47

AM

11:54

AM

12:01

PM

12:08

PM

12:15

PM

12:22

PM

12:29

PM

12:36

PM

12:43

PM

12:50

PM

12:57

PM

1:04 P

M

1:11 P

M

1:18 P

M

1:25 P

M

1:32 P

M

1:39 P

M

1:46 P

M

1:53 P

M

2:00 P

M

2:07 P

M

2:14 P

M

2:21 P

M

2:28 P

M

2:35 P

M

2:42 P

M

2:49 P

M

2:56 P

M

3:03 P

M

3:10 P

M

3:17 P

M

3:24 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Proving Oven

SENSOR HEIGHT VALUE WET BULB DRY BULB GLOBERELATIVE HUMIDITY

Min 20.3 26.3 27.9 41

Max 22.8 30.3 32 52 Head

Average 22.0 29.5 30.9 43.3

Min 20.5 26.5 28.2 41

Max 23.3 30.6 32.1 56 Abdomen

Average 22.5 29.7 31.0 43.5

Min 19.4 25.6 26.6 39

Max 22.6 29.8 30.9 50 Ankle

Average 21.8 29.2 30.4 42.0

82

Position 4. Bakery Shop

Environmental Conditions - Bakery Shop (Head Height)

18

23

28

33

38

43

48

53

58

12:28

PM

12:35

PM

12:42

PM

12:49

PM

12:56

PM

1:03 P

M

1:10 P

M

1:17 P

M

1:24 P

M

1:31 P

M

1:38 P

M

1:45 P

M

1:52 P

M

1:59 P

M

2:06 P

M

2:13 P

M

2:20 P

M

2:27 P

M

2:34 P

M

2:41 P

M

2:48 P

M

2:55 P

M

3:02 P

M

3:09 P

M

3:16 P

M

3:23 P

M

3:30 P

M

3:37 P

M

3:44 P

M

3:51 P

M

3:58 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbDry GlobeRelative Humidity

Environmental Conditions - Bakery Shop (Abdomen Height)

0

10

20

30

40

50

60

70

12:28

PM

12:35

PM

12:42

PM

12:49

PM

12:56

PM

1:03 P

M

1:10 P

M

1:17 P

M

1:24 P

M

1:31 P

M

1:38 P

M

1:45 P

M

1:52 P

M

1:59 P

M

2:06 P

M

2:13 P

M

2:20 P

M

2:27 P

M

2:34 P

M

2:41 P

M

2:48 P

M

2:55 P

M

3:02 P

M

3:09 P

M

3:16 P

M

3:23 P

M

3:30 P

M

3:37 P

M

3:44 P

M

3:51 P

M

3:58 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbDry GlobeRelative Humidity

83

Environmental Conditions - Bakery Shop (Ankle Height)

18

23

28

33

38

43

48

53

58

12:28

PM

12:35

PM

12:42

PM

12:49

PM

12:56

PM

1:03 P

M

1:10 P

M

1:17 P

M

1:24 P

M

1:31 P

M

1:38 P

M

1:45 P

M

1:52 P

M

1:59 P

M

2:06 P

M

2:13 P

M

2:20 P

M

2:27 P

M

2:34 P

M

2:41 P

M

2:48 P

M

2:55 P

M

3:02 P

M

3:09 P

M

3:16 P

M

3:23 P

M

3:30 P

M

3:37 P

M

3:44 P

M

3:51 P

M

3:58 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbDry GlobeRelative Humidity

Bakery Shop

SENSOR HEIGHT VALUE WET BULB

(°C) DRY BULB

(°C) GLOBE

(°C) RELATIVE HUMIDITY

Min 18.8 23.9 24.7 43.0

Max 19.7 27.9 28.5 61.0 Head

Average 19.3 26.4 27.1 49.2

Min 19.3 23.8 24.7 44.0

Max 20.3 28.1 28.8 61.0 Abdomen

Average 19.8 26.4 27.1 49.9

Min 19.3 24.0 24.9 43.0

Max 20.3 27.9 28.7 58.0 Ankle

Average 19.9 26.5 27.2 48.4

84

Environmental Conditions - Croissant Line (Head Height)

18

23

28

33

38

11:16

AM

11:24

AM

11:32

AM

11:40

AM

11:48

AM

11:56

AM

12:04

PM

12:12

PM

12:20

PM

12:28

PM

12:36

PM

12:44

PM

12:52

PM

1:00 P

M

1:08 P

M

1:16 P

M

1:24 P

M

1:32 P

M

1:40 P

M

1:48 P

M

1:56 P

M

2:04 P

M

2:12 P

M

2:20 P

M

2:28 P

M

2:36 P

M

2:44 P

M

2:52 P

M

3:00 P

M

3:08 P

M

3:16 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Bulb WetBulb DryGlobeRelative Humidity

Environmental Conditions - Croissant Line (Abdomen Height)

17

22

27

32

37

42

47

11:16

AM

11:22

AM

11:28

AM

11:34

AM

11:40

AM

11:46

AM

11:52

AM

11:58

AM

12:04

PM

12:10

PM

12:16

PM

12:22

PM

12:28

PM

12:34

PM

12:40

PM

12:46

PM

12:52

PM

12:58

PM

1:04 P

M1:1

0 PM

1:16 P

M1:2

2 PM

1:28 P

M1:3

4 PM

1:40 P

M1:4

6 PM

1:52 P

M1:5

8 PM

2:04 P

M2:1

0 PM

2:16 P

M2:2

2 PM

2:28 P

M2:3

4 PM

2:40 P

M2:4

6 PM

2:52 P

M2:5

8 PM

3:04 P

M3:1

0 PM

3:16 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Bulb WetBulb DryGlobeRelative Humidity

85

Environmental Conditions - Croissant Line (Ankle Height)

15

20

25

30

35

40

11:16

AM

11:23

AM

11:30

AM

11:37

AM

11:44

AM

11:51

AM

11:58

AM

12:05

PM

12:12

PM

12:19

PM

12:26

PM

12:33

PM

12:40

PM

12:47

PM

12:54

PM

1:01 P

M

1:08 P

M

1:15 P

M

1:22 P

M

1:29 P

M

1:36 P

M

1:43 P

M

1:50 P

M

1:57 P

M

2:04 P

M

2:11 P

M

2:18 P

M

2:25 P

M

2:32 P

M

2:39 P

M

2:46 P

M

2:53 P

M

3:00 P

M

3:07 P

M

3:14 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Bulb WetBulb DryGlobeRelative Humidity

Bakery Croissant Line

SENSOR HEIGHT VALUE WET BULB(°C)

DRY BULB(°C)

GLOBE(°C)

RELATIVE HUMIDITY

Min 19.5 27.5 29.0 21.0 Max 21.7 35.9 36.5 38.0 Head

Average 20.5 32.4 33.4 24.6 Min 17.6 26.9 27.6 28.0 Max 20.6 32.4 33.0 47.0 Abdomen

Average 19.1 29.6 30.1 32.6 Min 16.7 25.4 26.2 32.0 Max 19.6 30.2 34.9 39.0 Ankle

Average 17.8 27.5 28.6 35.7

86

Cake Oven

Environmental Conditions - Cake Oven (Head Height)

18

23

28

33

38

43

48

10:55

AM

11:03

AM

11:11

AM

11:19

AM

11:27

AM

11:35

AM

11:43

AM

11:51

AM

11:59

AM

12:07

PM

12:15

PM

12:23

PM

12:31

PM

12:39

PM

12:47

PM

12:55

PM

1:03 P

M

1:11 P

M

1:19 P

M

1:27 P

M

1:35 P

M

1:43 P

M

1:51 P

M

1:59 P

M

2:07 P

M

2:15 P

M

2:23 P

M

2:31 P

M

2:39 P

M

2:47 P

M

2:55 P

M

3:03 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Environmental Conditions - Cake Oven Abdomen Height

18

23

28

33

38

43

48

53

10:55

AM

11:03

AM

11:11

AM

11:19

AM

11:27

AM

11:35

AM

11:43

AM

11:51

AM

11:59

AM

12:07

PM

12:15

PM

12:23

PM

12:31

PM

12:39

PM

12:47

PM

12:55

PM

1:03 P

M

1:11 P

M

1:19 P

M

1:27 P

M

1:35 P

M

1:43 P

M

1:51 P

M

1:59 P

M

2:07 P

M

2:15 P

M

2:23 P

M

2:31 P

M

2:39 P

M

2:47 P

M

2:55 P

M

3:03 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

87

Environmental Conditions - Cake Oven (Ankle Height)

16

21

26

31

36

41

10:55

AM

11:03

AM

11:11

AM

11:19

AM

11:27

AM

11:35

AM

11:43

AM

11:51

AM

11:59

AM

12:07

PM

12:15

PM

12:23

PM

12:31

PM

12:39

PM

12:47

PM

12:55

PM

1:03 P

M

1:11 P

M

1:19 P

M

1:27 P

M

1:35 P

M

1:43 P

M

1:51 P

M

1:59 P

M

2:07 P

M

2:15 P

M

2:23 P

M

2:31 P

M

2:39 P

M

2:47 P

M

2:55 P

M

3:03 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Cake Oven

SENSOR HEIGHT

VALUE WET BULB

(°C) DRY BULB

(°C) GLOBE

(°C) RELATIVE HUMIDITY

Min 19.1 26.4 28.6 29.0

Max 21.6 32.1 32.6 47.0 Head

Average 20.6 30.6 31.1 31.0

Min 18.6 26.1 28.7 29.0

Max 21.5 31.6 32.5 53.0 Abdomen

Average 20.3 30.0 30.8 32.5

Min 17.4 26.3 27.8 29.0

Max 19.8 30.0 31.2 40.0 Ankle

Average 18.7 28.6 29.7 30.9

88

Foundry

Environmental Conditions - Head Height

18

23

28

33

38

43

48

53

10:06

AM

10:14

AM

10:22

AM

10:30

AM

10:38

AM

10:46

AM

10:54

AM

11:02

AM

11:10

AM

11:18

AM

11:26

AM

11:34

AM

11:42

AM

11:50

AM

11:58

AM

12:06

PM12

:14 PM

12:22

PM12

:30 PM

12:38

PM12

:46 PM

12:54

PM1:0

2 PM

1:10 P

M1:1

8 PM

1:26 P

M1:3

4 PM

1:42 P

M1:5

0 PM

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobe TemperatureRelative Humidity

Environmental Conditions - Abdomen Height

18

23

28

33

38

43

48

53

58

63

10:06

AM

10:14

AM

10:22

AM

10:30

AM

10:38

AM

10:46

AM

10:54

AM

11:02

AM

11:10

AM

11:18

AM

11:26

AM

11:34

AM

11:42

AM

11:50

AM

11:58

AM

12:06

PM

12:14

PM

12:22

PM

12:30

PM

12:38

PM

12:46

PM

12:54

PM

1:02 P

M

1:10 P

M

1:18 P

M

1:26 P

M

1:34 P

M

1:42 P

M

1:50 P

M

1:58 P

M

2:06 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

) Wet BulbDry BulbGlobe TemperatureRelative Humidity

89

90

SENSOR HEIGHT VALUE WET BULB

(°C) DRY BULB

(°C) GLOBE

(°C) RELATIVE HUMIDITY

Min 19.1 23.0 26.2 39.0

Head Max 21.8 29.5 30.3 60.0

Average 20.6 27.8 28.8 41.5

Min 18.8 23.3 25.6 45.0

Abdomen Max 20.6 27.1 29.1 60.0

Average 19.7 26.1 27.5 48.2

Min 18.4 21.8 25.3 46.0

Ankle Max 20.6 26.6 27.5 59.0

Average 19.4 24.0 26.0 52.2

Foundry

Environmental Conditions - Ankle Height

17

22

27

32

37

42

47

52

57

10:06

AM

10:14

AM

10:22

AM

10:30

AM

10:38

AM

10:46

AM

10:54

AM

11:02

AM

11:10

AM

11:18

AM

11:26

AM

11:34

AM

11:42

AM

11:50

AM

11:58

AM

12:06

PM

12:14

PM

12:22

PM

12:30

PM

12:38

PM

12:46

PM

12:54

PM

1:02 P

M

1:10 P

M

1:18 P

M

1:26 P

M

1:34 P

M

1:42 P

M

1:50 P

M

1:58 P

M

2:06 P

M

Time

Tem

pera

ture

(°) R

elat

ive

Hum

dity

(%)

Wet BulbDry BulbGlobeRelative Humidity

Glass Factory

Environmental Conditions - Head Height

15

20

25

30

35

40

10:58

AM

11:43

AM

12:28

PM

1:13 P

M

1:58 P

M

2:43 P

M

3:38 P

M

4:23 P

M

5:08 P

M

5:43 P

M

6:28 P

M

7:13 P

M

7:58 P

M

8:43 P

M

9:28 P

M

10:13

PM

10:58

PM

11:43

PM

12:28

AM

1:13 A

M

1:58 A

M

2:43 A

M

3:28 A

M

4:13 A

M

4:58 A

M

5:43 A

M

6:28 A

M

7:13 A

M

7:58 A

M

8:43 A

M

9:28 A

M

10:13

AM

10:58

AM

11:43

AM

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet Bulbdry bulbGlobeRelative Humidity

Environmental Conditions - Abdomen Height

15

2

35

3:24

45

20

5

30

40

PM

4: P

09M

4:54 P

M

10:59

AM

11:44

AM

12:29

PM

1:14 P

M

1P

:59 M

2:44 P

M

5:29 P

M

6:14 P

M

6:59 P

M

7:44 P

M

89 P:2

M

9:14 P

M

9:59 P

M

10:44

PM

11:29

PM

12:14

AM

12:59

AM

1:44 A

M

2:29 A

M

3:14 A

M

3:59 A

M

44 A:4

M

5:29 A

M

6:14 A

M

6:59 A

M

7:44 A

M

8:29 A

M

9:14 A

M

9:59 A

M

10:

A44

M

11:29

AM

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry bulbGlobeRe umlative H idity

91

Environmental Conditions - Ankle height

14

19

24

29

34

39

44

49

54

10:58

AM

11:58

AM

12:58

PM

1:58 P

M

2:58 P

M

4:08 P

M

5:08 P

M

5:58 P

M

6:58 P

M

7:58 P

M

8:58 P

M

9:58 P

M

10:58

PM

11:58

PM

12:58

AM

1:58 A

M

2:58 A

M

3:58 A

M

4:58 A

M

5:58 A

M

6:58 A

M

7:58 A

M

8:58 A

M

9:58 A

M

10:58

AM

11:58

AM

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet Bulbdry bulbGlobeRelative Humidity

Glass Factory

SENSOR HEIGHT VALUE

WET BULB(°C)

DRY BULB(°C)

GLOBE (°C)

RELATIVE HUMIDITY

Min

15.5 22.9 25.4 28.0

HEAD Max 32.5 31.7 33.5 43.0

Average 19.3 27.3 29.4 34.0

Min 16.7 24.5 30.0 25.0

Abdomen Max 21.2 33.6 37.7 40.0

Average 19.3 29.2 33.9 31.6

Min 14.9 20.2 22.7 32.0

Ankle Max 20 30.3 31.9 52.0

Average 17.6 25.5 28.3 39.6

92

93

Supermarket Distribution Centre: Set 1

Environmental Conditions - Set 1 Head Height

0

10

20

30

40

50

60

10:57

AM

11:05

A

11:13

AM

11:21

A

11:29

A

11

M M M:37

AM

11:45

AM

11:53

AM

12:01

PM

12:09

PM

12:17

PM

12:25

PM

12:33

PM

12:41

PM

12:49

PM

12:57

PM

1:05 P

M

1:13 P

M

1:21 P

M

1:29 P

M

1:37 P

M

1:45 P

M

1:53 P

M

2:01 P

M

2:09 P

M

2:17 P

M

2:25 P

M

2:33 P

M

2:41 P

M

2:49 P

M

2:57 P

M

e

Tem

pera

ture

(°C

) rel

ativ

e H

umid

ity (%

)

Wet BulbDry bulbGlobeRelative Humidity

Tim

Environm Conditio et 1 (Abd eight)

10

20

40

50

60

70

10:57

AM

11:05

A

11:

AM

11:21

AM

11:29

AM

11:3

11:

11:

12:

12:09

PM

12:17

12 12:

PM

12:41

PM

12:49

PM

12:57

M

1:21 P

M

1:29 P

M

1:37 P

1:41 P

M

2:09 P

M

2:17 P

M

2:25 P

M

2:33

M

2:57 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (°

C)

ental ns - S omen H

0

30

M13 7 A

M45

AM53

AM01

PM PM:25

PM33

PM

1:05 P

M

1:13 P

M5 P

M

1:53 P

M

2:0 PM

2:41 P

M

2:49 P

Wet BulbDry bulbGlobeRelative H midityu

Environmental Conditions - Set 1 Ankle Height

7.5

8.5

9.5

10.5

11.5

12.5

13.5

14.5

10:57

AM

11:05

AM

11:13

AM

11:21

AM

11:29

AM

11:37

AM

11:45

AM

11:53

AM

12:01

PM

12:09

PM

12:17

PM

12:25

PM

12:33

PM

12:41

PM

12:49

PM

12:57

PM

1:05 P

M

1:13 P

M

1:21 P

M

1:29 P

M

1:37 P

M

1:45 P

M

1:53 P

M

2:01 P

M

2:09 P

M

2:17 P

M

2:25 P

M

2:33 P

M

2:41 P

M

2:49 P

M

2:57 P

M

Time

Tem

pera

ture

(°C

) R

elat

ive

Hum

idity

(5)

Wet BulbDry bulbGlobeRelative Humidity

Supermarket Distribution Centre

SENSOR HEIGHT VALUE WET BULB(°C)

DRY BULB(°C)

GLOBE(°C) RELATIVE HUMIDITY

Min 8.3 11.2 11.5 45.0

Head Max 10.8 15.4 14.4 68.0

Average 10.0 13.0 13.2 59.0

Min 8.6 11.3 11.3 46.0

Abdomen Max 11.9 16.6 15.4 69.0

Average 10.2 13.1 12.9 60.4

Min 8.0 11.1 11.1 46.0

Ankle Max 10.1 14.5 13.9 70.0

Average 9.5 12.6 12.6 59.9

94

Supermarket Distribution Centre

Environmental Conditions - Set 2 Head Height

0

10

20

30

40

50

60

70

80

11:0

11:1

11:

11:3

11:3

11:4

11:

12:

12:1

12:1

12:2

126 A

M4 A

M22

AM

0 AM

8 AM

6 AM54

AM02

PM0 P

M8 P

M6 P

M:34

PM

12:42

PM

12:50

PM

12:58

PM

1:06 P

M

1:14 P

M

1:22 P

M

1:30 P

M

1:38 P

M

1:46 P

M

1:54 P

M

2:02 P

M

2:10 P

M

2:18 P

M

2:26 P

M

2:34 P

M

2:42 P

M

2:50 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

iry (°

C)

Wet BulbDry BulbGlobe TemperatureRelative Humidity

Enviro al Condit et 2 H ight

0.5

1

2

2.5

3

4

11:06

A

11:13

A

11:20

A

11:27

AM

11:34

AM

11:41

AM

:02 PM

:09 PM

12:16

PM

1:23

PM0 P

M

12:37

PM

12:44

PM

12:51

PM:58

PM5 P

M

1:12 P

M

1:19 P

M PM PM

1:40 P

M

1:47 P

M

1:54 P

M

2:01 P

M

2:08 P

M PM PM

2:29 P

M

Time

Tem

pera

ture

(°C

)

nment ions - S ead He

0

M M M

1.5

3.5

11:48

A

11:55

A

12 12

M M

2 12:3

12 1:0 1:26

1:33

2:15

2:22

Wet BulbDry BulbGlobe ature

Note: The e a consequence ofthreshold limi ithin the d isition system, whic perature

Temper

"clipped curves" ar tation wh is tem

ata acqurelated.

95

Environmental Conditions - Set 2 Head Height

30

35

40

45

50

55

60

65

70

75

80

11:06

AM

11:13

AM

11:20

AM

11:27

AM

11:34

AM

11:41

AM

11:48

AM

11:55

AM

12:02

PM

12:09

PM

12:16

PM

12:23

PM

12:30

PM

12:37

PM

12:44

PM

12:51

PM

12:58

PM

1:05 P

M

1:12 P

M

1:19 P

M

1:26 P

M

1:33 P

M

1:40 P

M

1:47 P

M

1:54 P

M

2:01 P

M

2:08 P

M

2:15 P

M

2:22 P

M

2:29 P

M

2:36 P

M

2:43 P

M

2:50 P

M

Time

Rel

ativ

e H

umid

ity (%

) Relative Humidity

Environmental Conditions - Set 2 Abdomen Height

0

10

20

30

40

50

60

70

80

90

11:06

AM

11:14

AM

11:22

AM

11:30

AM

11:38

AM

11:46

AM

11:54

AM

12:02

PM

12:10

PM

12:18

PM

12:26

PM

12:34

PM

12:42

PM

12:50

PM

12:58

PM

1:06 P

M

1:14 P

M

1:22 P

M

1:30 P

M

1:38 P

M

1:46 P

M

1:54 P

M

2:02 P

M

2:10 P

M

2:18 P

M

2:26 P

M

2:34 P

M

2:42 P

M

2:50 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

96

Environmental Conditions - Set 2 Abdomen Height

35

40

45

50

55

60

65

70

75

80

85

11:06

AM

11:14

AM

11:22

AM

11:30

AM

11:38

AM

11:46

AM

11:54

AM

12:02

PM

12:10

PM

12:18

PM

12:26

PM

12:34

PM

12:42

PM

12:50

PM

12:58

PM

1:06 P

M

1:14 P

M

1:22 P

M

1:30 P

M

1:38 P

M

1:46 P

M

1:54 P

M

2:02 P

M

2:10 P

M

2:18 P

M

2:26 P

M

2:34 P

M

2:42 P

M

2:50 P

M

Time

Rel

ativ

e H

umid

ity (%

) Relative Humidity

97

Environmental Conditions - Set 2 Abdomen Height

0

0.5

1

1.5

2

2.5

3

3.5

4

11:06

AM

11:13

AM

11:20

AM

11:27

AM

11:34

AM

11:41

AM

11:48

AM

11:55

AM

12:02

PM

12:09

PM

12:16

PM

12:23

PM

12:30

PM

12:37

PM

12:44

PM

12:51

PM

12:58

PM

1:05 P

M

1:12 P

M

1:19 P

M

1:26 P

M

1:33 P

M

1:40 P

M

1:47 P

M

1:54 P

M

2:01 P

M

2:08 P

M

2:15 P

M

2:22 P

M

2:29 P

M

Time

Tem

pera

ture

(°C

)

Wet BulbDry BulbGlobe

Note: The "clipped curves" are a consequence of threshold limitation within the data acquisition system, which is temperature related.

Environmental Conditions - Set 2 Ankle Height

0

0.5

1

1.5

2

2.5

3

3.5

11:06

AM

11:13

AM

11:20

AM

11:27

AM

11:34

AM

11:41

AM

11:48

AM

11:55

AM

12:02

PM

12:09

PM

12:16

PM

12:23

PM

12:30

PM

12:37

PM

12:44

PM

12:51

PM

12:58

PM

1:05 P

M

1:12 P

M

1:19 P

M

1:26 P

M

1:33 P

M

1:40 P

M

1:47 P

M

1:54 P

M

2:01 P

M

2:08 P

M

2:15 P

M

2:22 P

M

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

) Wet BulbDry BulbGlobe

Note: The "clipped curves" are a consequence of threshold limitation within the data acquisition system, which is temperature related.

Environmental Conditions - Set 2 Ankle Height

30

40

50

60

70

80

90

11:06

AM

11:13

AM

11:20

AM

11:27

AM

11:34

AM

11:41

AM

11:48

AM

11:55

AM

12:02

PM

12:09

PM

12:16

PM

12:23

PM

12:30

PM

12:37

PM

12:44

PM

12:51

PM

12:58

PM

1:05 P

M

1:12 P

M

1:19 P

M

1:26 P

M

1:33 P

M

1:40 P

M

1:47 P

M

1:54 P

M

2:01 P

M

2:08 P

M

2:15 P

M

2:22 P

M

2:29 P

M

2:36 P

M

2:43 P

M

2:50 P

M

Time

Tem

pera

ture

(°) R

elat

ive

Hum

idity

(%)

Relative Humidity

98

Supermarket Distribution Centre

SENSOR HEIGHT VALUE WET BULB

(°C) DRY BULB

(°C) GLOBE

(°C) RELATIVE HUMIDITY

Min 1.0 1.0 1.0 35

Head Max 10.2 13.3 13.5 78

Average 2.4 2.4 2.7 69.7

Min 1.0 1.0 1.0 38.0

Abdomen Max 10.1 12.9 13.4 82.0

Average 2.3 2.8 2.4 71.4

Min 1.0 1.0 1 37.0

Ankle Max 9.9 13.3 13.1 83.0

Average 2.2 2.4 2.4 73.1

99

Steel Foundry

Environmental Conditions - Set 1 Abdomen Height

5

15

25

35

45

55

65

15:53

:07

16:38

:07

17:23

:07

18:08

:07

18:53

:07

19:38

:07

20:23

:07

21:13

:07

21:58

:07

22:43

:07

23:28

:07

0:13:0

7

0:58:0

7

1:48:0

7

2:33:0

7

3:18:0

7

4:03:0

7

4:48:0

7

5:33:0

7

6:18:0

7

7:03:0

7

7:48:0

7

8:33:0

7

9:18:0

7

10:03

:07

10:48

:07

11:33

:07

12:18

:07

13:03

:07

13:48

:07

14:33

:07

15:18

:07

Time

Tem

pera

ture

(°C

) rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

Environmental Conditions - Set 1 Head Height

5

15

25

35

45

55

3:53:0

7 PM

4:38:0

7 PM

5:23:0

7 PM

6:08:0

7 PM

6:53:0

7 PM

7:38:0

7 PM

8:23:0

7 PM

9:08:0

7 PM

9:53:0

7 PM

10:38

:07 PM

11:23

:07 PM

12:08

:07 A

M

12:53

:07 A

M

1:38:0

7 AM

2:23:0

7 AM

3:08:0

7 AM

3:53:0

7 AM

4:38:0

7 AM

5:23:0

7 AM

6:08:0

7 AM

6:53:0

7 AM

7:38:0

7 AM

8:23:0

7 AM

9:08:0

7 AM

9:53:0

7 AM

10:38

:07 A

M

11:23

:07 A

M

12:08

:07 PM

12:53

:07 PM

1:38:0

7 PM

2:23:0

7 PM

3:08:0

7 PM

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

Wet BulbDry BulbGlobeRelative Humidity

100

Environmental Conditions - Set 1 Ankle Height

0

10

20

30

40

50

15:53

:07

16:38

:0

13:0

7

18:08

:07

18:53

:07

19:38

:07

20 21:53

:07

22:38

:07

23:23

:07

0: 1:38:0

7

2:23:0

7

3:08:0

5:23:0

7

6:08:0

7

6:53:0

7

73:0

7

9:08:0

7

9:53:0

7

10:38

:07

11:23

:07

12:08

:07

1207

15:08

:07

Time

Tem

pera

ture

(°C

) Rel

ativ

e H

umid

ity (%

)

60

70

7

7:2 :23:07

21:08

:0708

:07

0:53:0

7 7

3:53:0

7

4:38:0

7:38

:07

8:2 :53:07

13:38

:07

14:23

:

Wet BulbDry BulbGlobeRelative Humidity

Steel oundr

SENSOR HEIGHT VALUE WET BULB(°C)

DRY BULB(°C)

GLOBE(°C) RELATIVE HUMIDITY

oundr

SENSOR HEIGHT VALUE WET BULB(°C)

DRY BULB(°C)

GLOBE(°C) RELATIVE HUMIDITY

FF y y

Min 7.6 9.7 10.9 23

Head Max 16.7 22.1 41.8 62

Average 10.7 14.6 16.0 48.7

Min 7.6 9.9 10.9 23.0

Abdomen Max 16.0 22 31.7 62.0

Average 10.7 14.7 15.5 48.5

Min 8.2 10.5 11.7 28.0

Ankle Max 17.0 21.6 36.7 62.0

Average 10 15.1 16.5 49.2

101

APPENDIX 3 PARTICIPANT INFORMATION

hool of Sport and Leisure Management

search Ethics Committee

rticipant Information Sheet

oject Title The Effects of Thermal Environments on Manual Handling Tasks.

me of Participant

pervisor/Director of Studies Dr. John Saxton

ncipal Investigator Andy Davies

r

pose of Study and Brief Description of Procedures t a legal explanation but a simple statement)

e purpose of the study is to examine the effects of hot and cold working environments on manual handling ks. The results of this study will give us valuable information that will be used to produce guidelines for ustry hopefully resulting in a safer working environment.

u will be asked to lift a box onto a shelf at different lifting speeds. At the end of each lift another person l return the box to the starting position prior to the start of the next lift. The researcher will specify the ed at which they wish you to lift (e.g. 6 lifts per minute) and will give guidance accordingly. You should ure that you lift in accordance with the health and safety training that you have received within your anisation.

will be necessary for you to wear some testing equipment during the session. This will be as lightweight unobtrusive as possible. A heart rate monitor chest band will be worn next to the skin. Additionally, small

mperature sensors will be fixed to the skin with surgical tape and worn in the ears using ear plugs.

he Environment Chamber: u will receive acclimatization or orientation training on 5 consecutive days in the chamber. After this you l be required to attend 15 further sessions on consecutive working days. During these sessions both the quency of lift and temperature will be varied. These sessions should last no longer than 2 hours each.

ur assistance in this study is entirely voluntary and you are free to withdraw at any time without giving any son.

as been made clear to me that, should I feel that these Regulations are being infringed or that my interests are erwise being ignored, neglected or denied, I should inform Professor Edward Winter, Chair of the School of ort and Leisure Management Research Ethics Committee (Tel: 0114 225 4333) who will undertake to estigate my complaint.

102

APPENDIX 4 PRE-SCREENING QUESTIONNAIRE

103

chool of Sport and Leisure Management

esearch Ethics Committee

articipant Information Sheet

oject Title The Effects of Thermal Environments on Manual Handling Tasks

me of Participant

pervisor/Director of Studies Dr. John Saxton

ncipal Investigator Andy Davies

rpose of Study and Brief Description of Procedures ot a legal explanation but a simple statement)

e purpose of the study is to examine the effects of hot and cold working environments on manual ndling tasks. The results of this study will give us valuable information that will be used to duce guidelines for industry hopefully resulting in a safer working environment.

u will be asked to lift a box onto a shelf at different lifting speeds. At the end of each lift another son will return the box to the starting position prior to the start of the next lift. The researcher will

ecify the speed at which they wish you to lift (e.g. 6 lifts per minute) and will give guidance cordingly. You should ensure that you lift in accordance with the health and safety training that u have received within your organisation. will be necessary for you to wear some testing equipment during the session. This will be as htweight and unobtrusive as possible. A heart rate monitor chest band will be worn next to the n. Additionally, small temperature sensors will be fixed to the skin with surgical tape and worn in ears using ear plugs.

he Environment Chamber: u will receive acclimatization or orientation training on 5 consecutive days in the chamber. After s you will be required to attend 15 further sessions on consecutive working days. During these ssions both the frequency of lift and temperature will be varied. These sessions should last no ger than 2 hours each.

ur assistance in this study is entirely voluntary and you are free to withdraw at any time without ng any reason.

as been made clear to me that, should I feel that these Regulations are being infringed or that my

erests are otherwise being ignored, neglected or denied, I should inform Professor Edward Winter, air of the School of Sport and Leisure Management Research Ethics Committee (Tel: 0114 225 33) who will undertake to investigate my complaint.

104

APPENDIX 5 PSYCHOPHYSICS SCRIPT

"We want you to imagine that you are on piece work, getting paid for the amount of work that you do, but working a normal 8-hour shift that allows you to go home without feeling shattered. In other words, we want you to work as hard as you can without straining yourself, or without becoming unusually tired, weakened, overheated, or out of breath. You will adjust your own workload. You will lift only when you hear the audio tone. In some sessions you will be working fast, some sessions working slowly. Your job will be to adjust the weight of the box that you are lifting. Adjusting your own workload is not an easy task. Only you know how you feel. If you feel you are working too hard, reduce the load. Take some weight out of the box. We don’t want you loafing either. If you feel that you can work harder, increase the load. Put some weight into the box. Don’t be afraid to make adjustments. You have to make enough adjustments so that you get a good feeling for what is too heavy and what is too light. You can never make too many adjustments-but you can make too few. Remember… This is not a contest Everyone is not expected to do the same amount of work We want your judgement on how hard you can work without becoming unusually tired." Adapted from Ciriello, Snook & Hughes (1993).

105

Printed and published by the Health and Safety ExecutiveC30 1/98

Printed and published by the Health and Safety ExecutiveC1.10 04/05

RR 337

£25.00 9 78071 7 62995 4

ISBN 0-7176-2995-3