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Identifying Risk Factors

Safety Memo - Strains and Sprains OUCH!

Screening for Risk Factors

Screening jobs for physical and psychological risk factors is very proactive and should involve one or more of the following:

  • Walk-through observational surveys of the work facilities to detect obvious risk factors
  • Interviews with workers and supervisors to obtain the above information and other data not apparent in walk-through observations such as; time and workload pressures, length of rest breaks, etc.
  • Checklists for scoring job features against a list of risk factors

A great deal of research has been conducted to identify workplace factors that contribute to the development of musculoskeletal disorders. NIOSH has recently summarized the epidemiological studies that show a relationship between specific work activities and the development of musculoskeletal disorders.

According to the scientific literature, the following are recognized as important risk factors for musculoskeletal disorders, especially when occurring at high levels and in combination.

Physical risk factors include:

  • Awkward postures
  • Forceful exertions
  • Repetitive motions
  • Duration of exposure
  • Frequency of exposure
  • Contact stresses
  • Vibration
  • Other conditions

Let's take a closer look at each of these risk factors.

Physical Risk Factors

Awkward Postures

Body postures determine which joints and muscles are used in an activity and the amount of force or stresses that are generated or tolerated. For example, more stress is placed on the spinal discs when lifting, lowering, or handling objects with the back bent or twisted, compared with when the back is straight. Manipulative or other tasks requiring repeated or sustained bending or twisting of the wrists, knees, hips, or shoulders also impose increased stresses on these joints. Activities requiring frequent or prolonged work over shoulder height can be particularly stressful.

Forceful Exertions (including lifting, pushing, and pulling)

Tasks that require forceful exertions place higher loads on the muscles, tendons, ligaments, and joints. Increasing force means increasing body demands such as greater muscle exertion along with other physiological changes necessary to sustain an increased effort. Prolonged or recurrent experiences of this type can give rise to not only feelings of fatigue but may also lead to musculoskeletal problems when there is inadequate time for rest or recovery.

Force requirements may increase with:

  • Increased weight of a load handled or lifted
  • Increased bulkiness of the load handled or lifted
  • Use of an awkward posture
  • The speeding up of movements
  • Increased slipperiness of the objects handled (requiring increased grip force)
  • The presence of vibration (e.g., localized vibration from power hand tools leads to use of an increased grip force)
  • Use of the index finger and thumb to forcefully grip an object (i.e., a pinch grip compared with gripping the object with your whole hand)
  • Use of small or narrow tool handles that lessen grip capacity
Repetitive Motions

If motions are repeated frequently (e.g., every few seconds) and for prolonged periods such as an 8-hour shift, fatigue and muscle-tendon strain can accumulate. Tendons and muscles can often recover from the effects of stretching or forceful exertions if sufficient time is allotted between exertions. Effects of repetitive motions from performing the same work activities are increased when awkward postures and forceful exertions are involved. Repetitive actions as a risk factor can also depend on the body area and specific act being performed.

Physical Risk Factors (Continued)


Duration refers to the amount of time a person is continually exposed to a risk factor. Job tasks that require use of the same muscles or motions for long durations increase the likelihood of both localized and general fatigue. In general, the longer the period of continuous work (e.g., tasks requiring sustained muscle contraction), the longer the recovery or rest time required.


Frequency refers to how many times a person repeats a given exertion within a given period of time. Of course, the more often the exertion is repeated, the greater the speed of movement of the body part being exerted. Also, recovery time decreases the more frequently an exertion is completed. And, as with duration, this increases the likelihood of both localized and general fatigue.

Contact Stresses

Repeated or continuous contact with hard or sharp objects such as non-rounded desk edges or unpadded, narrow tool handles may create pressure over one area of the body (e.g., the forearm or sides of the fingers) that can inhibit nerve function and blood flow.


Exposure to local vibration occurs when a specific part of the body comes in contact with a vibrating object, such as a power hand tool. Exposure to whole-body vibration can occur while standing or sitting in vibrating environments or objects, such as when operating heavy-duty vehicles or large machinery.

Other Conditions

Workplace conditions that can influence the presence and magnitude of the risk factors for MSDs can include:

  • cold temperatures,
  • insufficient pauses and rest breaks for recovery,
  • machine paced work, and
  • unfamiliar or unaccustomed work.

Psychological Risk Factors


In addition to the above conditions, other aspects of work may not only contribute to physical stress but psychological stress as well. As long as we believe we have adequate control over all aspects of our job, we may experience normal stress. However, if we believe we have little control over job demands, we may suffer from distress with accompanying ill health and possible irrational behaviors. Under distress, the probability of an accident increases greatly.

Research is examining work factors such as performance monitoring, incentive pay systems, and unreasonable management production demands to determine whether these factors have a negative effect on the musculoskeletal system. Another related area of research is to determine which personal, work, or societal factors contribute to acute musculoskeletal disorders developing into chronic or disabling problems.

Using a Checklist

The checklist is a formal and orderly procedure for screening jobs. Numerous versions of checklists exist in ergonomics manuals.

When checklist data are gathered by persons familiar with the job, task, or processes involved, the quality of the data is generally better.

This checklist illustrates three processes:

  • Assessment - identify to determine if something is present.
  • Analysis - take it apart to determine what it looks like, how it works.
  • Evaluation - judge it against the best.

This checklist first assesses for risk factors by asking if something is present. You merely place a check in the appropriate box.

Using the checklist in the next tab, you can identify the general risk factors associated with the job you currently perform.

Ergonomic Risk Analysis Checklist

Manual Material Handling
  1. Is there lifting of loads, tools, or parts?
  2. Is there lowering of tools, loads, or parts?
  3. Is there overhead reaching for tools, loads, or parts?
  4. Is there bending at the waist to handle tools, loads, or parts?
  5. Is there twisting at the waist to handle tools, loads, or parts?
Physical Energy Demands
  1. Do tools and parts weigh more than 10 lb?
  2. Is reaching greater than 20 in.?
  3. Is bending, stooping, or squatting a primary task activity?
  4. Is lifting or lowering loads a primary task activity?
  5. Is walking or carrying loads a primary task activity?
  6. Is stair or ladder climbing with loads a primary task activity?
  7. Is pushing or pulling loads a primary task activity?
  8. Is reaching overhead a primary task activity?
  9. Do any of the above tasks require five or more complete work cycles to be done within a minute?
  10. Do workers complain that rest breaks and fatigue allowances are insufficient?
Other Musculoskeletal Demands
  1. Do manual jobs require frequent, repetitive motions?
  2. Do work postures require frequent bending of the neck, shoulder, elbow, wrist, or finger joints?
  3. For seated work, do reaches for tools and materials exceed 15 in. from the worker's position?
  4. Is the worker unable to change his or her position often?
  5. Does the work involve forceful, quick, or sudden motions?
  6. Does the work involve shock or rapid buildup of forces?
  7. Is finger-pinch gripping used?
  8. Do job postures involve sustained muscle contraction of any limb?

Ergonomic Risk Analysis Checklist (Continued)

Computer Workstation
  1. Do operators use computer workstations for more than 4 hours a day?
  2. Are there complaints of discomfort from those working at these stations?
  3. Is the chair or desk nonadjustable?
  4. Is the display monitor, keyboard, or document holder nonadjustable?
  5. Does lighting cause glare or make the monitor screen hard to read?
  6. Is the room temperature too hot or too cold?
  7. Is there irritating vibration or noise?
  1. Is the temperature too hot or too cold?
  2. Are the worker's hands exposed to temperatures less than 70 degrees Fahrenheit?
  3. Is the workplace poorly lit?
  4. Is there glare?
  5. Is there excessive noise that is annoying, distracting, or producing hearing loss?
  6. Is there upper extremity or whole body vibration?
  7. Is air circulation too high or too low?

Ergonomic Risk Analysis Checklist (Continued)

General Workplace
  1. Are walkways uneven, slippery, or obstructed?
  2. Is housekeeping poor?
  3. Is there inadequate clearance or accessibility for performing tasks?
  4. Are stairs cluttered or lacking railings?
  5. Is proper footwear worn?
  1. Is the handle too small or too large?
  2. Does the handle shape cause the operator to bend the wrist in order to use the tool?
  3. Is the tool hard to access?
  4. Does the tool weigh more than 9 lbs?
  5. Does the tool vibrate excessively?
  6. Does the tool cause excessive kickback to the operator?
  7. Does the tool become too hot or too cold?
  1. Do the gloves require the worker to use more force when performing job tasks?
  2. Do the gloves provide inadequate protection?
  3. Do the gloves present a hazard of catch points on the tool or in the workplace?
  1. Is there little worker control over the work process?
  2. Is the task highly repetitive and monotonous?
  3. Does the job involve critical tasks with high accountability and little or no tolerance for error?
  4. Are work hours and breaks poorly organized?
Here's a great NIOSH resource for more information: Ergonomics Guidelines for Manual Material Handling.


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. The purpose of the walk-through observational survey is to _____.

2. The quality of the checklist data collected is generally better when _____.

3. The checklist procedure provides a formal and orderly procedure for screening jobs.

4. Force requirements may increase with _____.

5. Screening jobs for physical and psychological risk factors should involve _____.

Have a great day!

Important! You will receive an "error" message unless all questions are answered.