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Ergonomic Glossary - Risk Factors

For ease of browsing, this glossary is divided into the following six sections:

RISK FACTORS

Awkward Posture: Posture describes the position of the body while performing work activities. Awkward posture is associated with an increased risk for injury. It is generally considered that the more a joint deviates from the neutral (natural) position, the greater the risk of injury. Certain awkward postures used while performing activities have been associated with increased risk of injury.

Duration: The continuous time a task is performed without an adequate rest break. It can be measured as the minutes or hours per day the worker is exposed to a risk as well as in the length of time in years that an employee is performing similar tasks. In general, the greater the duration of exposure to a risk factor, the greater the degree of risk.

Contact Stress: Exposure of a body part to a hard or sharp surface continuously, repetitively or forcefully at a workstation or on a tool (such as when gripping a tool or leaning on the edge of a desk).

Continuous Work: Work activities that are sustained and uninterrupted. Continuous work, especially when the work is demanding, results in earlier fatigue than does intermittent work.

Cycle: A time interval during which a regularly occurring sequence of events is completed. A cycle can be the time to complete a job with many tasks or the time to produce one section of the job.

Fatigue: The reduction in performance ability caused by a period of excessive activity followed by inadequate recovery time. Muscle fatigue is accompanied by a buildup of lactic acid in the working muscle.

Force: The amount of muscular effort required to perform a task. Generally, the greater the force, the greater the degree of risk.

Heat Stress: Exposure to a hot environment that reduces the capability for sustained activity and speeds up fatigue.

Lighting: The level of illumination in the workplace. Poor lighting can lead to eye-strain and fatigue.

Manual Material Handling: Any handling task such as lifting, carrying, and moving materials that is performed without mechanical assist.

Motion: Velocity/Acceleration - Velocity/ acceleration is the speed of body part motion and the rate of change of speed of body part motion, respectively. It is generally regarded that increased acceleration leads to increased risk of injury.

Recovery Time: Recovery time is the length of rest between exertions. Short work pauses can reduce discomfort. Inadequate rest periods between exertions can decrease performance. As the duration of the uninterrupted work increases, so does the amount of recovery time needed.

Repetition: Repetition is the number of a similar exertions performed during a task or during a certain period of time. High frequency of repetitive motions has been associated with injury and worker discomfort.

Risk Factor: Actions in the workplace, workplace conditions, or a combination thereof, that may cause or aggravate the risk of a work place injury. Examples of high risk factors include forceful exertions, awkward postures, repetitive exertions, and environmental factors such as temperature.

Static Exertion: Static exertions refer to physical job demands (gripping, holding a posture) in which the same position or posture is held throughout the task (also referred to as "static loading").

Task: A subunit of a job or the group of activities that accomplishes the work objective or job.

Torque (Moment): A force that produces or tends to produce rotation; the rotational force about a point (e.g., torque is the force required to tighten a bolt). Excessive torque forces increase the risk of work place injuries, particularly to the upper extremities and especially to the elbow.

Vibration: The oscillatory motion of a physical body. Localized vibration, such as hand-arm vibration, is produced by contact with powered tools or equipment or with vibrating structures. Whole-body vibration occurs while standing or seated in vibrating environments or objects, such as trucks or heavy machinery.

Work Cycle: The work cycle consists of an exertion period and a recovery (or smaller exertion) period necessary to complete one sequence of a task, before the sequence is repeated.

Work Methods: The physical methods used to perform the tasks of a job, such as reaching, gripping, using tools and equipment, or discarding objects.

Work Recovery Cycles: The job pattern that defines how work is organized with respect to lighter tasks or rest. High work/recovery ratios, measured as continuous time on each type of activity, have higher potential for fatigue.

Workstation: The entire area accessed by a worker when performing a specific task or job cycle.

SOURCES USED DURING THIS COMPILATION OF ERGONOMIC TERMS:

Marji Hajic is an Occupational Therapist and a Certified Hand Therapist practicing at the Hand Therapy & Occupational Fitness Center in Santa Barbara, California. For more information on hand and upper extremity injuries, prevention and recovery, visit

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