Psychophysically determined horizontal and vertical forces of dynamic pushing on high and low coefficient of friction floors for female industrial workers.

The purpose of this experiment was to investigate horizontal and vertical components of maximum acceptable initial and sustained forces while performing pushcart tasks on high and low coefficient of friction (COF) floors. Eleven female industrial workers performed two sessions of 120 pushcart tasks on a high COF (.68) floor and one session of 120 pushcart tasks on a low COF (.26) floor. Each pushcart task was 7.6 meters long and initiated once a minute. A psychophysical methodology was employed whereby the workers were asked to select a work load they could sustain for 8 hours without "straining themselves or without becoming unusually tired, weakened, overheated, or out of breath." The results revealed that maximum acceptable weights of the pushcart task on the low COF floor were significantly lower (20%) than the maximum acceptable weights on the high COF floor, which coincided with a significant reduction in the initial and sustained horizontal forces of push (28% and 29%, respectively) on a low COF floor. Push durations on the low COF floor were also significantly longer (36%) than on the high COF floor. Vertical forces and ratios of the vertical to horizontal forces were not significantly different comparing both floors. Calculated probabilities of slipping were supported by observations of repeated slipping by some workers during pushing on the low COF floor. Ergonomic strategies should include the maintenance of sufficient COF on floors to maximize the psychophysical pushing capabilities of the industrial worker.