Ergonomic Risk Factors
Ergonomic risk factors are conditions of a job, process or operation that contribute to the risk of developing work-related musculoskeletal disorders (MSDs). This includes damaged muscles, nerves, tendons, ligaments, joins, cartilage or spinal disks. The main ergonomic risk factors that can cause MSDs are awkward postures, forceful exertions and repetitive motions.
According to the Bureau of Labor Statistics, MSDs are the single largest category of workplace injuries and are responsible for almost 30 percent of all workers' compensation costs. Workers suffering from an MSD average 12 days away from work. To reduce the frequency and severity of MSDs in the workplace, it is important to eliminate ergonomic risk factors that are known to contribute to their development.
Posture determines which joints and muscles are used in an activity. It also affects the amount of force required to perform a job. For example, more stress is placed on spinal discs when lifting, lowering or handling objects when the back is bent or twisted than when the back is straight.
Tasks requiring repeated or sustained twisting of the wrists, knees, hips or shoulders create increased wear and tear on joints and muscles in those areas. And activities requiring frequent or prolonged work over shoulder height can be particularly stressful on the body.
Work that involves forceful exertions—such as lifting, pulling, pushing, gripping or pinching—place higher loads on muscles, tendons, ligaments, joints, cartilage, and spinal discs. Prolonged or frequent activities with high amounts of force can cause fatigue. If there is inadequate time for rest and recovery, these activities can lead to musculoskeletal problems. Force requirements may increase with:
- Increased weight and bulkiness of the load being handled or lifted
- Increased speed or acceleration of movement (e.g., jerkiness)
- Presence of localized or whole-body vibration
- Use of the index finger and thumb to forcefully grip an object (i.e., a pinch grip compared to a power grip)
- Use of small or narrow tools that limit grip capacity.
If motions are repeated frequently and for long periods of time, like an eight-hour shift, a buildup of fatigue and muscle tendon strain can occur. Tendons and muscles often recover from the effects of stretching or forceful exertions if there is sufficient time between exertions. Repetitive motion is especially dangerous when combined with other risk factors, such as awkward postures or forceful exertions.
Tasks that require the use of the same muscle groups for long periods of time increase the likelihood of fatigue. In general, the longer the period of continuous work, the longer the recovery time required.
Repeated or continuous contact with hard or sharp objects—such as nonrounded desk edges or unpadded, narrow tool handles—can create pressure over one area of the body (e.g., the forearm or sides of the fingers) and reduce nerve function and blood flow.
There are two types of vibration: local and whole body. Local vibration occurs when part of the body comes into contact with a vibrating object, such as a power hand tool. Exposure to whole-body vibration can occur while sitting or standing in vibrating environments or objects, such as heavy-duty vehicles or large machinery.
Workplace conditions that can influence the presence and magnitude of these risk factors include:
- Temperature extremes
- Not enough recovery time
- Machine or assembly line paced work
Eliminate Risk Factors
The best way to control ergonomic risk factors is to first watch employees performing their jobs. Be sure to document any risk factors using an ergonomic risk factor checklist and develop methods to eliminate them. Checklists of ergonomic risk factors are a good way to ensure that all risks have been considered during the observation.
If risk factors are present, determine their severity, duration and frequency. For example, if an employee lifts a heavy object (forceful exertion), determine how much the object weighs, how long it takes to perform the lift and how often the lift is required. The more information you have about the task, the easier it will be to develop solutions.
The three common methods used to control ergonomic risk factors are:
- Engineering controls—Changes to the process, workstation layout, tool designs or material handling techniques to reduce or eliminate hazardous conditions
- Administrative controls—Changes to work practices and management policies, such as longer breaks, job rotation, adjusting work pace and employee training
- Personal protective equipment (PPE)—Equipment such as wrist braces and antivibration gloves; PPE is the least effective method and should be used as a last resort
Evaluate Control Effectiveness
A follow-up evaluation is necessary to ensure that the implemented controls have eliminated or reduced the ergonomic risk factors and that no new risk factors have been introduced. The follow-up assessment should use the same format as the initial evaluation that documented the risk factors. If the risk factors have not been eliminated or reduced, more work should be done.
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