Attentional demands and postural sway: the effect of the calf muscles fatigue

The purpose of the present experiment was to investigate whether the calf muscle fatigue affects postural sway in bipedal stance and requires additional attentional demands. Nine healthy university students had to respond as rapidly as possible to an unpredictable auditory stimulus while maintaining stable seated and upright postures with their eyes closed in two conditions of no-fatigue and fatigue of the calf muscles. Center of foot pressure (COP) displacements were recorded using a force platform. Reaction times (RTs) values were used as an index of the attentional demand necessary for regulating postural sway. Fatigue yielded a significant anterior shift of mean position of the COP and increased range, mean speed, and dispersion of COP displacements. An increased attentional demand for regulating postural sway also was observed with fatigue. These results suggest that muscular fatigue may put the individuals at higher risk of falling, especially when engaging in concurrent tasks.