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711 Introduction to Ergonomics
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Duration

Duration is a measure of length of time of exposure to a risk factor.

Long hours of hard work can cause fatigue and eventual injury.

Of course, the assumption is that the longer the duration of exposure, the greater the risk of injury. Duration may be measured in seconds, minutes, hours, days, weeks, months, and even years.

When evaluating individual risk factors, it is important to take into account other factors such as the worker's physical conditioning, posture, force, weight, temperature, stress,etc. Duration of exposure is just one of the many factors that must be considered.

Recovery Time

Recovery time is the period of rest or low-stress activity available to a muscle group between similar exertions. Adequate recovery time allows muscles to restore energy, receive oxygen and nutrients, and clear metabolic byproducts. It also helps reduce fatigue and lowers the risk of discomfort, strain, and work-related musculoskeletal disorders.

The recovery time needed depends on the physical demands of the task. Longer, more forceful, or more repetitive tasks generally require longer recovery periods. Awkward or static postures may also increase recovery needs because sustained muscle contractions can restrict blood flow. Employers can improve recovery by providing rest breaks, rotating employees among tasks that use different muscle groups, and reducing excessive force, repetition, and task duration.

Knowledge Check Choose the best answer for the question.

3-7. Recovery time needed will _______ as the duration of the task increases.