Psychophysiological responses in women during cart pushing on different frictional walkways

The aim of this study was to evaluate psychophysically determined acceptable forces, cardiopulmonary, and calf muscle metabolic responses in 15 workers while they pushed an instrumented cart on two walkways.

In addition to the potential for increased musculoskeletal disorders in workers, pushing on various terrains is associated with occurrence of slips and falls at the workplace.

Using a psychophysical approach, participants chose the maximum acceptable cart weight they could push without strain on walkways with coefficient of friction equaling 0.68 (plywood) and 0.26 (Teflon-coated.). Then, while participants pushed their psychophysically chosen cart weight for 2 hr on each walkway, horizontal and vertical forces applied on the cart handle and physiological responses were collected. Cardiopulmonary responses were measured using a telemetric metabolic cart. A tissue hemoglobin index (THI) and a tissue oxygenation index (TOI) from the right and left calf muscles were obtained using near-infrared spectroscopy.

Participants generated higher horizontal forces (by 26%) on plywood than that on Teflon. Cardiopulmonary and TOI and THI responses were similar between walkways. However, greater ratios of absolute oxygen uptake per force (by 19%) and TOI per force (by 24%) on Teflon were demonstrated in the horizontal direction than on plywood.

This increased muscle oxygenation-force ratio, coupled with increased oxygen uptake per force generated on Teflon, might suggest that pushing on the slippery surface results in higher metabolic demand.

Findings from the present study will assist in revising previously established acceptable forces and in relating these forces to physiological responses with respect to pushing on different frictional walkways.