Repetition
Repetition is a measure of how frequently we complete the same motion or exertion during a task.
The severity of risk depends on the frequency of repetition, speed of the movement or action, the number of muscle groups involved, and the required force. Repetitiveness is influenced by machine or line pacing, incentive programs, piece work, and unrealistic deadlines.
For instance, an experienced worker packing apples (piece work) may complete many more similar exertions or movements than a new worker. Unfortunately, he or she may be performing at such a rapid rate that they may be developing a CTD.
Cumulative Trauma Disorder (CTD) is a term used to describe a range of injuries that result from repeated physical actions or sustained postures over a prolonged period. These injuries typically affect the musculoskeletal system and can result in pain, discomfort, and functional limitations in affected body parts such as hands, wrists, forearms, shoulders, and neck.
Repetition alone is not an accurate predictor of injury. Other factors like force, posture, duration, and recovery time must also be considered. See a chart on high risk repetition rates.
| Body Part | Repetitions Per Minute |
|---|---|
| Shoulder | More than 2 1/2 |
| Upper Arm/Elbow | More than 10 |
| Forearm/Wrist | More than 10 |
| Finger | More than 200 |
From Kilbom... [1994]. Repetitive work of the upper extremity; Part II: The scientific basis for the guide. Int J Ind Erg 14:59 - 86.
Caution: Do not judge the risk of MSDs solely on the basis of repetition. Much depends on force and the postural factors that reflect the intensity of each action. High repetitiveness, when combined with high external forces and extreme postures, presents the highest risk of MSDs.
Knowledge Check Choose the best answer for the question.
3-6. Which of the terms below is defined as a measure of how frequently we complete the same motion or exertion during a task?
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