The effects of cycle time on the physical demands of a repetitive pick-and-place task.

This study seeks to elucidate the effects of the cycle time of a pick-and-place task on muscle activity, grip force, posture, and perception-based measures (discomfort and difficulty). Six healthy adults (3 males, 3 females) participated. A 4 x 2 repeated measures design was used with cycle time (1, 2, 5, and 10s) and grip (power and chuck) as independent variables. The task consists of repetitively picking a 0.7 kg part and placing it into a bin. A reduction in cycle time (CT) resulted in both a decrease of task time and physical rest time (p<0.001). The physiological muscle rest was much lower than the physical rest time (p<0.05). An increase in static muscle loading (p<0.01), grip force (p<0.001), and discomfort (p<0.001) were also observed. These results suggest that a pace threshold (between 2 and 5s for this task) is reached at a higher CT than that defined by the ability to perform the task.