Department Of Defense Ergonomics Working Group

Department of DefenseErgonomics Working GroupErgonomics AwarenessErgonomics DefinedErgonomics is the study of how to fit theworkplace to the worker. While the use ofthe term ergonomics has become morecommon recently, Ergonomics is not a newscience. The term was actually coined in1857 by a Polish scholar.The key points to remember are that ergonomicsshould: Fit the workplace to the worker Not fit the worker to the workplace2

Department of DefenseErgonomics Working GroupErgonomics AwarenessIncorrect: The individual accommodates themselves to their surroundings in order toperform their workA worker should not have to adjust themselves toaccommodate their workplace setup. If a workermust adjust to fit their workplace they becomeat risk to sustain a work related musculoskeletaldisorder or WMSD.The image above is an example of a workerthat must adapt to her workplace. Prolongedperiods in this posture could cause neck, eye,shoulder, back, or hand strain.3

Department of DefenseErgonomics Working GroupErgonomics AwarenessCorrect: The workspace has been modified to fit theworker.To reduce the risk of WMSDs, the workplace should bedesigned to fit the worker, as seen in the image. The individualno longer has to extend their neck back to view the monitorbecause the monitor, chair, and key-board have beenrepositioned. This is an example of a workplace that isfit to the worker.By adjusting the monitor to improve thesightline and neck posture, andadjusting the chair to maximize neutralposition, this workplace better fits theworker.4

Department of DefenseErgonomics Working GroupErgonomics AwarenessImportance of ergonomicsThe application of ergonomics can: Improve health and safety through the reductionof ergonomics risk factors and resultingwork-related injuries and disordersSupport mission readinessImprove comfort, morale, productivity andjob satisfactionReduce workers compensation costs andemployee turn over5

Department of DefenseErgonomics Working GroupErgonomics AwarenessOne Work-related Musculoskeletal Disorder Injury Affects Many PeopleInjuries affect not only the worker,but the people they interact with as well.6

Department of DefenseErgonomics Working GroupErgonomics AwarenessInjuries- Musculoskeletal Disorder (MSD)MSDs are a category of injuries and disorders that deal with themusculoskeletal system. These disorders are not usually causedby acute trauma but instead occur slowly over time due to wearand tear on the nervous system and soft tissues, such as: MusclesTendonsLigamentsCartilageNervesMSDs are preventable but everyone is at risk.7

Department of DefenseErgonomics Working GroupErgonomics AwarenessWork-related Musculoskeletal Disorders (WMSDs)WMSDS are MSDs that are caused or aggravated by workmethods and/or environments. WMSDs do not generallyresult from a single event or accident, but rather aredisorders that have developed gradually from chronicworkplace and occupational conditions causing repeatedtrauma.Common WMSDs include: Tendonitis Epicondylitis Bursitis Trigger Finger Carpal Tunnel Syndrome Herniated Spinal Disc8

Department of DefenseErgonomics Working GroupErgonomics AwarenessWMSDs AliasesWMSDs go by other names, including: Repetitive Strain or Stress Injury (RSI)Repetitive Motion Injury (RMI)Cumulative Trauma Disorder (CTD)Overuse SyndromeActivity Related Pain SyndromeSome people who have been diagnosed with a disorder such as carpal tunnel syndrome may notknow that it is a part of the category of injuries known as WMSDs.9

Department of DefenseErgonomics Working GroupErgonomics AwarenessRisk FactorsThere are two types of risk factors for developing WMSDs:Physical- the characteristics of the job that place the workerat risk of developing a WMSD, but which usually canbe modified.Contributing- the characteristics of the person or job thatcontribute to, but not cause, WMSDs and which usually cannot be changed. Contributing risk factors are frequentlydifficult to control.10

Department of DefenseErgonomics Working GroupErgonomics AwarenessPhysical Risk FactorsPhysical work place risk factors can cause WMSDs to develop. The risk factors must occur incombination to present a risk of WMSDs and they typically magnify each other as a result. There aresix common physical risk factors related to WMSDs: Compression or Contact StressPosition or posture Vibration Non-NeutralStaticWhole bodyHand-armForceRepetitionDuration11

Department of DefenseErgonomics Working GroupErgonomics AwarenessCompression or Contact StressCompression occurs when an object presses on soft tissue. This concentration of force onsmall areas reduce blood flow and nerve transition and can damage the soft tissue.Compression occurs from: Leaning or pressing against hard edges,sharp surfaces, or corners Supporting excessive weight Gripping tools12

Department of DefenseErgonomics Working GroupErgonomics AwarenessNeutral Posture vs. Non-neutral PosturePosture or position dictates how hard the body works and howmuch effort the muscles must exert.Neutral posture maximizes strength, speed, endurance, andcomfort while decreasing the risk of WMSDs. Neutralposture is important because it promotes blood flow,nerve conduction, strength and control.Non-neutral posture stretches the physical limits and cancause muscle fatigue or micro trauma to tendons or ligaments,and compress or stretch soft tissues such as nerves.13

Department of DefenseErgonomics Working GroupErgonomics AwarenessWorking Neutral Posture DemonstrationThis video demonstrates the difference between neutral and non-neutral posture.14

Department of DefenseErgonomics Working GroupErgonomics AwarenessWorking Neutral sitting PostureYou can recognize neutral posture at a computer workstation by looking for these key landmarks. Hands, wrists and forearms are straight, in line and roughlyparallel with the floor. Head is level or bent slightly forward, forward facing andbalanced, generally the head is in line with the torso. Shoulders are relaxed and upper arms hang normally at theside of the body. Elbows are in close to the body and are bent between 90and 120 degrees. Feet are fully supported by the floor or footrest. Back is fully supported with appropriate lumbar supportwhen sitting vertically or leaning back slightly. Thighs and hips are supported by a well padded seat and aregenerally parallel to the floor. Knees are about the same height as the hips with the feetslightly forward.15

Department of DefenseErgonomics Working GroupErgonomics AwarenessPosture CorrectionHere are the posture corrections this medical technician needs to adjust or risk aWMSD. Ears are not over the shoulders.Shoulders are not over the hips.Hips are not over the knees.Hand is at an awkward angleand the arms are not at a 90 degreeangle.16

Department of DefenseErgonomics Working GroupErgonomics AwarenessStatic PostureHolding a posture for extended periods of time is known as static posture.Static postures prevent the flow of blood which bringsnutrients to the muscles and carries away waste products.Holding a muscle in contraction causes waste productsto build up and can lead to fatigue and discomfort.17

Department of DefenseErgonomics Working GroupErgonomics AwarenessVibrationVibration is another type of risk factor. A simple definition of vibration is rapidmovement back and forth; however, vibration involves the exposure tomovement against the body from all directions.Vibration occurs in two forms: Whole body Hand-arm18

Department of DefenseErgonomics Working GroupErgonomics AwarenessWhole Body VibrationWhole body vibration is caused by standing or sitting on a vibrating surface.The vibration works its way through the body and results in muscle fatigueand contraction.High or prolonged exposure to whole body vibrationcan effect the skeletal muscles and digestive systemand cause lower back disorders.19

Department of DefenseErgonomics Working GroupErgonomics AwarenessHand-Arm VibrationHand-arm vibration is usually caused when a worker holds a vibrating hand toolfor long periods of time. This action causes reduced blood flow to the fingersand can lead to blanching of the fingers or Raynaed’s syndrome. Cold weather isa contributing factor to vibration-related WMSDs.Some of the WMSDs associated with hand-armvibration are. Raynaed’s Syndrome Vibration induced white finger Carpal Tunnel Syndrome20

Department of DefenseErgonomics Working GroupErgonomics AwarenessForceForce is the use of power or exertion to move, direct or operate equipment. Theless force required to operate equipment, the less traumatic it is to the body.Excessive force exertion may cause the muscles to meet or exceed their maximumcapability resulting in muscle fatigue or injury. Repeated muscle trauma can resultin damage or injury.21

Department of DefenseErgonomics Working GroupErgonomics AwarenessHigh Force ExamplesHigh force risk factor can occur while lifting, carrying, pushing, pinching and gripping.Posture and position are important in considering high force risks.It is important to understand that strength varies by person and as individuals, we vary bytolerance and ability.The power zone for lifting with the greatest strength and lowest risk of injury is close tothe body between thigh and shoulder height. It is important to note lifting even a 20pound weight, one hundred times a day in a non-neutral posture may pose a high forcerisk.22

Department of DefenseErgonomics Working GroupErgonomics AwarenessRepetitionThe physical risk factor repetition is defined as performing the same motion or group of motionsexcessively, for example: Repeating the same motion every few seconds.Keeping a cycle of motions involving the same body parts/muscle groups.Using a tool or device in a steady manner.Repetition or use of the same body parts continuouslythroughout the workday can be damaging to the body.It is important to note that if you change the job but stilluse the same muscle group you are not doing anythingdifferent. Repetition is often seen in tasks such asassembly, typing, operating machinery, or loading andunloading a vehicle.23

Department of DefenseErgonomics Working GroupErgonomics AwarenessDurationHow long a task is performed or how frequently the same muscle groups are usedin a day contributes to the risk factor known as duration. Duration is defined as thetime period that a task is performed. Continuous or repeated exposure to one ormore of the other risk factors does not allow muscles time to recover and magnifiesother risk factors.The key point to remember is that the longer theduration, the greater the exposure and the greater the risk.Taking breaks, reducing the amount of time spent onsimilar tasks, and alternating between jobs that usedifferent actions can help reduce duration exposure.24

Department of DefenseErgonomics Working GroupErgonomics AwarenessPhysical Risk Factors ReviewPhysical factors have to occur in combination to pose a risk.Physical risk factors include: Compression Non-neutral, awkward or static posture Vibration High Forces Repetition DurationBy applying ergonomics principles to tasks, jobs and the work environment, physical riskfactors can usually be modified or reduced.25

Department of DefenseErgonomics Working GroupErgonomics AwarenessContributing Risk FactorsIn addition to the six physical risk factors, there are three important contributingrisk factors.Contributing risk factors can contribute to, but do not cause, WMSDs. For example,temperature and humidity affect the worker performing repetitive work. When it is too hotand too humid, workers fatigue more quickly and become more susceptible to injury.Contributing risk factors are generally harder to control than physical risk factors.Contributing risk factors include: Temperature Inadequate recovery Personal risk factors26