LOCOMOTOR-LIKE MOVEMENTS EVOKED BY LEG MUSCLE VIBRATION IN HUMANS

We attempted to elicit automatic stepping in healthy humans using appr opriate afferent stimulation. It was found that continuous leg muscle vibration produced rhythmic locomotor-like stepping movements of the s uspended leg, persisting up to the end of stimulation and sometimes ou tlasting it by a few cycles. Air-stepping elicited by vibration did no t differ from the intentional stepping under the same conditions, and involved movements in hip and knee joints with reciprocal electromyogr am (EMG) bursts in corresponding flexor and extensor muscles. The phas e shift between evoked hip and knee movements could be positive or neg ative, corresponding to 'backward' or 'forward' locomotion. Such an es sential feature of natural human locomotion as alternating movements o f two legs, was also present in vibratory-evoked leg movements under a ppropriate conditions. It is suggested that vibration evokes locomotor -like movements because vibratory-induced afferent input sets into act ive state the central structures responsible for stepping generation.