w4 work physiology1

Copyright Catherine M.

Burns 1

WORK PHYSIOLOGY

Physiology vs. Work Physiology

Physiology

The study of the functions of the body parts. ie.

How the body parts work.

Work Physiology

The study, description, evaluation, and explanation of the physiological changes in the human body resulting from either a single or repeated series of exposure to work stresses.

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Physiology

Work Physiology Making sure that individuals are not taking

part in tasks that exceed the energy requirements of the body.

Involved in setting standards for acceptable physical work rate and load.

Looks into the nutritional aspect of the individuals

Environmental Physiology Deals with the impact of physical working

conditions and sets optimum requirements Thermal

Noise

Vibration

Lighting

Systems Most Relevant To Work Physiology

Muscular (blood pressure, body temperature,

latic acid content)

Respiratory (sweating rate, oxygen

consumption)

Cardiovascular (heart rate)

Nervous

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Copyright Catherine M. Burns 5

Work Physiology

more a discussion of the energy side of

using muscles

rather than the mechanics/force side you

see in biomechanics

extends to metabolism, energy restrictions on

work and fatigue

How Do We USE Work Physiology?

To enhance EFFICIENCY To monitor

energy expenditure and avoid excess fatigue

To ensure SAFETY - do not push people

beyond their physical limitations.


Muscle Structure

Wickens Figure 12.1

Muscle, muscle fibre, myofibril, sarcomere

muscle muscle fiber myofibril

sarcomere


Sarcomere Construction

Two types of proteins actin (thin) and

myosin (thick)

Actin filaments slide over myosin filaments

to produce the contraction

Sliding filament theory of muscle contraction

long

Short (contracted)

myosin actin

z-line


Aerobic and Anaerobic Metabolism

Aerobic (Oxidative Phosphorylation)

nutrients

oxygen

energy ATP

CO2

muscles/work

Anaerobic (Anaerobic Glycolysis)

glucose

OP

AG energy

lactic acid

ATP muscles/work


Anaerobic Metabolism

Lactic acid causes muscle pain and fatigue

Anaerobic processes occur

at the start of work (first 1-3 minutes)

during heavy work


Muscle Efficiency

Muscle efficiency is only about 20%

The rest is lost as heat

Increases body temperature

Problems in working in hot environments


Circulatory System

blood delivers nutrients

and oxygen to the muscles

carries away carbon

dioxide and waste products

heart - pressure generating

blood pump

lungs - site of oxygen and

CO2 exchange

Heart



Heart Parameters

change with work, heat, stress

Major measures

cardiac output (Q): flow rate of blood through

the heart

5L/min resting

15L/min moderate work

25L/min heavy work


Heart Measures

Cardiac Output

function of heart rate (HR) x stroke volume (SV)

Q=HRxSV

Heart rate: beats per minute

Stroke

volume: litres of blood per beat

Heart Rate Cycle (Grandjean,1986)

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Heart Measures

Menggunakan alat cardio tachometer dan

pulse meter

Diukur secara manual dengan meraba

denyutan pada arteri radialis kemudian

dihitung dg rumus:

60_

/ xnperhitungaWaktu

DenyutmenitDenyut


Blood Flow Distribution

Changes with work

increases to muscles

more to skin in hot environments

Resting muscles 15-20%

Heavy work 70-75%

Also note temperature effect 40% of blood to skin

in the moderate work at 38 degree level


Respiratory System

Air exchange system

Measures

tidal volume: amount of air breathed per breath

0.5L resting

2L heavy work

minute ventilation: amount of air per minute

tidal volume x frequency

Body increases tidal volume first, then breathing

frequency


Total Lung Capacity

Residual Volume

(always there)

Vital Capacity (Maximum

Breathe in)

Tidal Volume (normal

breathe in, not max)

Inspiratory Reserve

Volume Expiratory Reserve

Volume

Residual Volume

(always there)

Tidal volume ranges from 0.5L to 2L

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Energy Cost of Work

Basal metabolic rate: lowest level of energy

expenditure needed to maintain life

1600-1800 kcal/day

1 kilocalori (kcal) = 4,2 kilojoule (kJ)

1 watt = 1 joule/sec

1 l Oxygen 4.8 kcal energy 20 KJ

varies with gender, age, weight

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Working metabolism: the increase in metabolism from resting to working level

Metabolic rate during work: sum of basal metabolic rate and working metabolic rate

Men (70 kg) : 1700 kcal / 24 h 1.2 Kcal/minutes

The woman (60 kg) : 1400 kcal / 24 h 1.0 Kcal/minutes

range: 1.6 to 16 kcal/min

sitting 1.6 kcal/min, walking 2.8 kcal/min

heavy work 5kcal and up


Measuring Physical Work

oxygen consumption rate

heart rate

linear relation between heart rate and energy

expenditure

see Figure 12.5


Physical Work Capacity

short term work capacity

also called aerobic capacity

about 15kcal/min men 10 kcal/min women

long term work capacity

suggested not over 1/3 of short term for 8 hrs

higher than this causes fatigue

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Fatigue

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Fatigue

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Fatigue


Fatigue

in this sense, body exceeds what can be

provided by aerobic metabolism

anaerobic metabolism meets energy needs

decreased blood glucose

increased lactic acid

also psychological and health factors

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Energy Cost of Work

Equation consumption of energy

Garg (1976) mengestimasi pengeluaran

energi pada pekerjaan pengangkatan beban

Astuti (1985) pengeluaran energy dengan

kecepatan denyut jantung

Rakhmaniar (2007) regresi hubungan

energi dengan kecepatan denyut jantung

Garg (1976)

Angkatan membungkuk (stoop lift )

E = 0,0109 BW (0,0012 BW + 0,0052 L + 0,0028 S x L)f

Angkatan Jongkok (squat lift )

E = 0,0109 BW + (0,0019 BW + 0,0081 L + 0,0023 S x L)f

Angkatan dengan tangan (arm lift )

E = 0,0109 BW + (0,0002 BW + 0,0103 L 0,0017 S x L)f

dengan :

E = pengeluaran energi (kkal/menit)

BW = berat badan (lbs)

L = berat angkatan (lbs)

S = jenis kelamin (pria = 1,wanita = 0)

F = frekuensi angkatan (angkatan/menit)

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Astuti (1985)

dengan :

Y = energi expenditure (Kkal/menit)

X = kecepatan denyut jantung/menit

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2-4 X4,71733.10 0,0229038X 1,80411 Y

Rakhmaniar (2007)

Y = 0.014 HR + 0.017 B 1.706

dengan :

Y = Konsumsi oksigen (liter/menit)

HR = Denyut jantung (denyut/menit), dan

B = Berat badan (kg)

1 liter/menit O2 = 4.8 kcal/menit energi.

Setelah dikonversi:

KE = Et Ei

Dengan :

KE = Konsumsi energi (kilokalori)

Et = Pengeluaran energi setelah kerja (kilokalori)

Ei = Pengeluaran energi saat istirahat (kilokalori)

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Waktu Istirahat

Lamanya waktu istirahat diharapkan cukup untuk menghasilkan

cadangan energi

Diasumsikan bahwa selama istirahat jumlah energi adalah 1,5 kcal/menit

Untuk mengestimasikan jumlah waktu untuk istirahat, dapat

diformulasikan sebagai berikut:

R = waktu istirahat yang diperlukan (menit)

T = Total waktu kerja (menit)

= Rata-rata energi yang dikonsumsikan untuk kerja (KCal./Menit)

S = Standart beban kerja normal yang diaplikasikan (Kcal/menit)

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)(5.1

)(menit

K

SKTR

K

Waktu kerja

Dengan:

Tw : waktu kerja (working time) (menit)

E : konsumsi energi selama pekerjaan berlangsung

(kcal/menit)

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Tugas Kelompok

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Penelitian terhadap sebuah pekerjaan fisik.

Hitunglah denyut jantung sebelum dan sesudah bekerja.

Hitung energy expenditure dengan 3 persamaan (Garg,

Astuti dan Rakhmaniar)

Hitung waktu kerja dan waktu istirahat yang seharusnya

diberikan.

Klasifikasi beban kerja

Analisis dan pembahasan.

w4 work physiology1

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