Influence of perceptual learning on standing posture balance: repeated training for hardness discrimination of foot sole

The current study investigated the influence of perceptual learning training for hardness discrimination of sponge rubber by the soles on postural sway. Subjects consisted of 30 healthy male volunteers. They were divided into two groups of 15 each at random: perceptual learning training group and a control group. For hardness discrimination training, rubber sponges 5, 10, and 20 mm thick were combined to change the thickness of rubber to 5, 10, 15, 20, and 25 mm. The hardness discrimination training was administered with eyes closed in the standing position for each day for 10 days. The center of pressure measured using a stabilometer was used as the indicator for postural sway. Postural sway was measured for 30 s with eyes open and closed before and after hardness discrimination training. Statistical analysis was performed for length, enveloped area, and rectangular area. Postural sway after training showed a significant decrease compared to sway before training in the perceptual learning training group. However, there was no change on postural sway in the control group. In conclusion, data indicate that the ability of the healthy subjects to regulate their standing posture improved with improvement of the perceptive ability of the soles.