Differential sensitivity to static visual cues in the control of postural equilibrium in man.

Decreasing the visual sampling rate by reducing the stroboscopic frequency affected the postural performance of human subjects. At low strobe frequencies of up to 2 flashes/sec., at which only static visual cues were available, no decrease in subjects' mean postural sway was previously observed as compared to their equilibrium behavior without vision. In this experiment, to test the hypothesis that there may be a differential sensitivity to static visual cues in the control of postural equilibrium, we examined the possible effects of subjects' sex and previous sports training on this sensitivity. The static postural equilibrium abilities of 70 subjects of both sexes were tested in a sharpened Romberg position. Performance was measured with accelerometers within a vertical cylinder under normal illumination, 2-Hz stroboscopic light, and darkness. Comparisons between the average postural performances under 2-Hz strobe light and darkness showed no significant differences between conditions. Analysis of subjects' individual scores showed that 27% of the sample performed significantly better under the strobe light than in darkness, 57% produced similar performances under both conditions, and 16% performed better in darkness. Although significant differences existed between the postural performances of men and women and between trained and untrained subjects, no differences were observed in the differential sensitivity to static visual cues depending on subjects' sex or on previous physical training.