Occupational Ergonomics: Reducing Risk in the Workplace

Editor’s Note: This article presents a review of risk management information from Ergonomics: The Study of Work, a report issued in 2000 by the U.S. Department of Labor Occupational Safety and Health Administration.

Ergonomics can be defined simply as the study of work. More specifically, ergonomics is the science of designing the job to fit the worker, rather than physically forcing the worker’s body to fit the job. Adapting tasks, work stations, tools and equipment to fit the worker can help reduce physical stress on a worker’s body and eliminate many potentially serious, disabling work-related musculoskeletal disorders (MSD). Ergonomics draws on a number of scientific disciplines, including physiology, biomechanics, psychology, anthropometry, industrial hygiene and kinesiology.

If work tasks and equipment do not include ergonomic principles in their design, workers may have exposure to undue physical stress, strain and overexertion, including vibration, awkward postures, forceful exertions, repetitive motion and heavy lifting. Recognizing ergonomic risk factors in the workplace is an essential first step in correcting hazards and improving worker protection.

What Are MSDs?
MSDs are injuries and disorders of the soft tissues—muscles, tendons, ligaments, joints and cartilage—and the nervous system. Occupational safety and health professionals have called these disorders a variety of names, including cumulative trauma disorders, repeated trauma, repetitive stress injuries and occupational overexertion syndrome. These painful and often disabling injuries generally develop gradually over weeks, months and years.

MSDs usually result from exposure to multiple risk factors that can cause or exacerbate the disorders, not from a single event or trauma such as a fall, collision or entanglement. MSDs can cause a number of conditions, including pain, numbness, tingling, stiff joints, difficulty moving, muscle loss, and sometimes paralysis. Frequently, workers must lose time from work to recover; some never regain full health. These disorders include carpal tunnel syndrome, tendonitis, sciatica, herniated discs and low back pain. MSDs do not include injuries resulting from slips, trips, falls or similar accidents.

Prolonged Risk Exposure
Work-related MSDs occur when the physical capabilities of the worker do not match the physical requirements of the job. Prolonged exposure to ergonomic risk factors can cause damage to a worker’s body and lead to MSDs. Conditions that are likely to cause MSD problems include the following:

  • Exerting excessive force
  • Excessive repetition of movements can irritate tendons and increase pressure on nerves
  • Awkward postures or unsupported positions can stretch physical limits, compress nerves and irritate tendons
  • Static postures or positions that a worker must hold for long periods of time can restrict blood flow and damage muscles
  • Motion, such as increased speed or acceleration when bending and twisting, can increase the amount of force exerted on the body
  • Compression, from grasping sharp edges like tool handles or resting body parts against hard surfaces, can concentrate force on small areas of the body, reduce blood flow, interrupt nerve transmission and damage tendons
  • Inadequate recovery time due to overtime, lack of breaks and failure to vary tasks can leave insufficient time for tissue repair
  • Excessive vibration—usually from vibrating tools—can decrease blood flow, damage nerves and contribute to muscle fatigue
  • Whole-body vibration from driving trucks can affect skeletal muscles and cause low-back pain
  • Cold temperatures can adversely affect a worker’s coordination and manual dexterity, causing them to use more force than necessary to perform a task

These risk factors, either alone or in combination, can subject workers’ shoulders, arms, hands, wrists, backs and legs to thousands of repetitive twisting, forceful or flexing motions during a typical workday. To contribute to MSDs, however, these risk factors must be present for a sufficient duration, frequency or magnitude.

Non-Work Related Factors
Risk factors not related to a worker’s job can also cause or contribute to MSDs. These factors include the following:

  • Physical conditioning
  • Medical conditions such as obesity, diabetes and arthritis
  • Pregnancy
  • Hobbies that are hand intensive or require manual handling (NOTE: Hobbies are generally not considered primary risk factors since participants can control the duration of and exposure to manual handling.)
  • Psychological or social workplace stress

Frequent Tendon Disorders
MSDs can affect nearly all tissues in the human body—nerves, tendons, tendon sheaths and muscles. The most frequently affected areas of the body are the arms and back.

Tendon disorders such as tendonitis, tenosynovitis, De Quervain’s disease, trigger finger and carpal tunnel syndrome are the most common occupational MSDs associated with the arm. Tendon disorders are very common and often occur at or near the joints where the tendons rub against other tendons, ligaments or bones. The most frequently noted symptoms of tendon disorders are a dull aching sensation over the tendon, discomfort with specific movements and tenderness to touch. Recovery is usually slow, and the condition may easily become chronic if the physical stresses causing the problem are not eliminated or reduced.

Another MSD that has received increased attention in recent years is carpal tunnel syndrome, or CTS, which affects the hands and wrists. CTS is the compression and entrapment of the median nerve where it passes through the wrist into the hand’s carpal tunnel. The median nerve is the main nerve that extends down the arm to the hand. It provides the sense of touch in the thumb, index finger, middle finger, and half of the fourth (or ring) finger. CTS develops in the hands and wrists from repetitive and forceful manual tasks performed without time to recover. Any worker whose job demands a lot of repetitive wrist, hand and arm motion that’s not necessarily forceful could develop CTS.

When irritated, tendons housed inside the narrow carpal tunnel swell and press against the nearby median nerve. The pressure causes tingling, numbness or severe pain in the wrist and hand—often felt while sleeping. Pressure also results in a lack of strength in the hand and an inability to make a fist, hold objects or perform other manual tasks. If the pressure continues, it can damage the nerve, causing permanent loss of sensation and even partial paralysis.

Back injury is another MSD that accounts for a significant loss of productivity and large workers’ compensation costs. Employees cite back disorders most often, after the common cold and flu, as reasons for missing work.

The most common back problems are pulled or strained muscles, ligaments and tendons. More serious disorders involve spinal discs. More than half the work force experience back pain at least once during a lifetime. When repetitive pulling and straining injures back muscles or ligaments, they can become scarred, weakened and lose their ability to support the back. This makes additional injuries more likely.

Prevention and Payback
Many solutions to ergonomic problems in the workplace are simple and inexpensive. Good ergonomics is good economics. For example, awkward and uncomfortable positions may be eliminated by taking one or more of the following steps for your employees:

  • Adjust the height of working surfaces
  • Vary tasks
  • Provide short breaks
  • Reduce the weight and size of items workers must lift
  • Put supplies and equipment within easy reach of the worker
  • Provide ergonomic chairs or stools
  • Provide telephone headsets
  • Supply anti-fatigue mats
  • Supply the right tool for the job

Providing a workplace free of ergonomic hazards can produce the following:

  • Lowered injury claim rates as MSD incidences go down
  • Increased productivity by making jobs easier and more comfortable for workers
  • Reduced absenteeism as workers need less time off to recover from muscle soreness, fatigue and MSD-related problems
  • Reduced employee turnover as new hires are more likely to find an ergonomically designed job within their physical capacity
  • Lowered Workers’ Compensation and health claims costs
  • Decreased employee attrition and replacement worker costs
  • Improved worker morale and safety

Avoid Workplace Hazards
MSDs are often easy to prevent. Effective ergonomic programs should be based upon a combination of management commitment and employee participation. If you are an employer whose workplace poses ergonomic risk factors or whose workers report MSDs, you can address this problem by providing opportunities for employees to participate in ergonomic trainings. Also, encourage your employees to become actively involved in regularly scheduled workplace health and safety programs.

Training programs will go a long way toward increasing safety awareness among managers, supervisors and employees. Training and education help ensure that employers sufficiently inform workers about ergonomic risk factors at their worksites so they are better able to participate actively in their own protection. Suggestions and input from workers aware of ergonomic risk factors can be very helpful in designing improved workplaces to reduce MSD hazards.

A good ergonomics training program will teach employees how to properly use equipment and tools as well as the correct way to perform job tasks. For example, to minimize or prevent back disorders, employers should teach workers to avoid long reaches, maintain neutral postures and use proper lifting techniques. Correct posture is also important whether an employee is sitting, standing, pulling, pushing, lifting, or using tools or equipment. General lifting techniques also can help reduce the strain leading to back disorders. For example, employees should use their leg muscles and bend their knees to pick up and lower heavy loads.

If you have the need for an ergonomics program at your worksite, New Hampshire Local Government Center’s (LGC) Risk and Health Management Department can help. A number of health and safety training resources are available that address ergonomics, back care and workplace safety. For more program information, visit www.nhlgc.org and click on “Training and Consulting".

MUSCULOSKELETAL DISORDERS

Risk Factors
Awkward postures
Bending and lifting
Static positions
Reaching
Force
Repetition
Contact stress
Vibration
Extreme temperatures

Body Parts Affected
Arms
Back
Hands
Wrists
Fingers
Legs
Neck
Shoulders