The pace of work determines the amount of time available for rest and recovery of the body between cycles of a particular task. A fast pace of work is a strong risk factor for WMSDs. If the pace is too fast, the muscles involved do not have enough time to recover from the effort and are prone to fatigue and injury. Externally imposed factors such as an assembly line speed, are especially hazardous because the worker has no control over the timing and speed of work, which also stresses the worker psychologically. Greater psychological stressors can inherently increase muscle tension, doubling the effects of fatigue and risk of injury. In the presence of such externally imposed factors, scheduling work breaks and rest breaks are important in the prevention of WMSD. When the work pace is internally imposed, incentive systems that reward for the quality of work naturally dictate a comfortable and safe work pace. Incentive systems to avoid are those that reward the quantity of work, as these increase the risk for WMSDs and may in the long run compromise quality as well.