Repetitive movements are especially hazardous when they involve the same joints and muscle groups over and over and when we do the same motion too often, too quickly and for too long. Tasks requiring repetitive movements always involve other risk factors for WMSD such as fixed body position and force; the worker, in order to perform the task, has to maintain the shoulder and neck in a fixed position to exert some force.
To analyze how repetitive a task is, we need to describe it in terms of steps or cycles. For example, the bottle packing operation (Figure 7) requires workers to pack boxes with twenty-four bottles.