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Laboratory Workers Commonly ReportWork-Related Musculoskeletal Disordersfrom the Use of Manual Pipettes� Ergonomic Science May Hold the Key to Prevention

by Kev in J . Cos te l l o , Cer t i f i ed Ergonomis t , The DuPont Company

The pipette is one of the most essentialtools in clinical and research laboratories.To develop new drugs and other laborato-ry-based innovations, or to perform diag-nostic tests, quality control, and qualityassurance procedures, laboratorians expendtremendous care and effort on examiningand testing chemical and biological materi-als. The process requires transferring pre-cise amounts of liquid and is typically performed manually using pipettes.Researchers and laboratory personnel usepipettes several hours daily and experiencefatigue and discomfort in the upper extrem-ities. With time and repetition, muscles,tendons, ligaments, nerves, and blood ves-sels can be damaged, resulting in injuriesknown as musculoskeletal disorders orMSDs. The most common of these injuriesor disorders reported among laboratoryworkers include carpal tunnel syndrome(CTS), tendinitis, epicondylitis (tenniselbow), tenosynovitis, trigger finger, cubitaltunnel syndrome, tarsal tunnel syndrome,and tension neck syndrome.

The ergonomic risks from pipetting areprimarily a result of awkward and staticworking postures. Lifting the upper arm infront of the body (upper arm flexion)between 45 and 90° is common throughoutthe pipetting task, and is coupled with fre-quent lifting of the elbow out to the side ofthe body (abduction of the arm). The handand wrist are usually over-rotated and/orbent, considerably diminishing musclestrength. Performing tasks in a fume hoodor booth exacerbates the stresses to theshoulder and neck. Additionally, repetitivetwisting of the forearm 180° betweenpalm-up and palm-down positions (prona-tion and supination of the forearm) is com-mon. (See page S-14.)

While it may be complicated to calcu-late exactly how much is too much whenevaluating exposure to ergonomic risks,the obvious contributing factors should beminimized to prevent fatigue, pain, andpotential injury. Our bodies are simplystronger, more efficient, and less injuryprone when we work within a range ofneutral positions and at acceptable levelsof repetition, force, and contact stress.

Various US governmental agencies,including NIOSH1, NIEHS2, and the CDC3

have suggested modifying certain laborato-ry practices as a means for reducing expo-

sures to risk factors when pipetting.Collectively, the recommendations includefocus in four key areas.

Minimize Awkward Posture:� Use shorter pipettes to reduce hand

elevations.� Position elbows as close to the body as

possible, with arms and wrists extend-ed in straight, neutral positions (hand-shake posture, palm slightly down).

� Keep work items within close reachto limit arm extension or twisting theneck and torso.

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� Minimize situations and time thatarms are in an elevated position.

� Use adjustable chairs or ergonomical-ly designed stools with proper back,thigh, and foot support.

� Use “low-profile” equipment (waste receptacles, solutioncontainers, etc.).

Minimize Force:� Select/use pipettes that require less

finger or thumb movement and physi-cal effort when aspirating or dispens-ing fluids.

� Use only the force necessary to perform a task (avoid unnecessaryexertion such as jamming on tips).

� Avoid repeated pounding with thebase of the palm (common whenapplying tips).

Minimize Repetition Effects:� Distribute tasks to minimize the

amount of continuous pipetting.� Share workload between right and left

sides of the body.� Vary tasks among pipettor types where

activation motions are different.� Rotate pipetting tasks among several

individuals.

Minimize Contact Stress:� Select/use pipettors that best fit the

user’s hand.� Select pipettes that use the full hand

with a relaxed grip span rather than atight grip (clenched fist).

� Avoid sharp or hard work surfaceswhen resting arms or elbows, provid-ing mats or rest pads as appropriate.

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Definitions� Repetition - the frequency at which a motion or task is duplicated with little variation in movement. For

many tasks in the laboratory, such as pipetting, it’s an unfortunate but unavoidable reality. The risk ofWMSDs due to repetition is increased when combined with force, contact stress, and awkward postures.

� Contact Stress - results from continuous contact between a hard object and sensitive tissues. Force and repetition combine to produce mechanical friction on soft tissue and tendons that is increased when forcefulexertion is used, such as a firm grip when holding a pipette. A recommended limit for maximum contactpressure during repetitive work is 26 to 57 psi for males, and 14 psi for females.

� Force - the physical effort needed to accomplish a motion or task. Force also refers to the stress or degreeof loading placed on muscles and other tissues, such as the additional physical effort that may be needed toperform tasks in an awkward position.

� Awkward Posture - positions of the body that deviate significantly from the neutral position while job tasksare performed, thereby increasing muscle load and effort. Examples of awkward posture as it applies topipetting would include over-rotation and/or bending of the wrist, a clenched hand, or suspension of the armhigh over the work surface.

0º 100% of Hand Strength

65º

55% Reduction

45º

20% Reduction

Flexion

Extension

Hand strength diminishes with wrist extension or flexion

Ergonomic experts have made addi-tional recommendations based on a number of studies:

� Wrist rotation should not exceed90° from the work surface.

� Arm/hand elevation should notexceed 12� from the work surface.

� Hand posture should remain relaxed.� Limit load levels (muscle activity)

to 15% MVC or below (MaximumVoluntary Contraction [MVC] is themaximum force a muscle can vol-untarily generate during a staticcontraction. For any given task, thehigher the %MVC, the greater therisk of fatigue and/or injury.).

� Use pipettes that accommodate variations in user hand sizes.

� Use pipettes with improved usabilityfor volume adjustment, grip textures,lab bench storage, character legibility,and minimized contamination.

� Keep work items within close reachto support a comfort zone.

While specific data for laboratory-oriented environments has only beenselectively collected and reported to date,

preliminary studies indicate that trends inthe laboratory are consistent with indus-try at large in terms of injury prevalenceand costs. U.S. employers are currentlypaying in excess of $15 billion per yearin workers’ compensation costs for work-related musculoskeletal disorders andassociated expenses4. Of larger concernis the significant cost to employers in

process inefficiency, product quality, andemployee productivity. According to arecent yearlong survey of active workersin the United States, lost productive timefrom common pain conditions costsindustry an estimated $61.2 billion per year. Most pain-related lost produc-tive time occurs while employees are at work, and is in the form of reducedperformance5.

Research has also shown that forevery dollar invested in an ergonomicsintervention strategy, there is a return of$17.804. With education and purchaseand use of the right tools for the job,employee health and safety, process effi-ciency, product quality, and productusability will increase, while dollarsspent in lost work time due to pain, sur-gery, or physical therapy will decrease.To this end it is important for laborato-ries to develop an overall ergonomicstrategy as an integral part of their oper-ating strategy. By applying a greaterunderstanding of how human perform-ance issues contribute to production bot-tlenecks, quality control problems,injury, and turnover rates, significantergonomic improvements can beachieved in the laboratory work environ-ment. For those who use pipettes in thecourse of their work, its possible to mini-mize the health and safety issues associ-ated with the task by using productsdesigned specifically to operate withneutral alignments of the upper armextremities. In all likelihood this willreduce overall musculoskeletal injuriesand improve job performance and satisfaction.

References1. National Institute for Occupational

Safety and Health2. National Institute of

Environmental Health Sciences3. Office of Health and Safety

System of the Centers for DiseaseControl and Prevention

4. Stewart et al, JAMA 2003;290:2443-2454

5. Buckle 1999

� VistaLab Technologies, Inc.27 Radio Circle DriveMt. Kisco, NY 10549

Use InfoLINK 4D2105 or Call 800-369-0153

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