Closed-loop Tactile Augmentation by Transcutaneous Stimulation on either the Foot Sole or the Palm to Improve Lateral Postural Balance

The objective of this study is to provide insight on the impact of closed-loop tactile augmentation on either the foot sole or the palm on postural regulation, specifically when plantar cutaneous feedback is reduced. To accomplish this objective, two healthy human subjects stood on a lateral balance board and maintained their balance for as long as possible until the balance board contacted the ground. Subjects were instructed to close their eyes during the experiment to remove visual feedback and increase the dependency on the tactile feedback for balancing. Balance time was measured both with and without a layer of foam on top of the balance board, to test the effect of reduced tactile feedback from the foot sole. The effects of tactile augmentation on the foot sole or the palm were tested by applying transcutaneous electrical stimulation on the calcaneal nerve or the ulnar nerve during the balance test with the foam layer in place. The average balance times of the subjects were decreased by the foam, which indicates the importance of plantar cutaneous feedback on postural balance. The average balance times of the subjects were increased by tactile augmentation, either on the foot sole or on the palm. This result suggests that closed-loop augmentation of tactile sensation can be a promising way to improve postural regulation, particularly for individuals with compromised plantar cutaneous feedback.