Effects of reversal in the human equilibrium regulation system

The postural reactions induced in man by bilateral vibration of the tibial muscles under various conditions were investigated: sitting with feet not in contact with support; sitting in an unstable position on a narrow seat; sitting with feet in contact with different types of support (suspended platform, turntable, etc.); standing with an asymmetrical load applied to the body. It was demonstrated that local vibration of the tibial muscles can induce not only activation of the vibrated muscle or of its antagonist (local effects), but excitation of the extensors and flexors of the knee joint (nonlocal effects) or remote muscle groups participating in the realization of various postural synergies. The specific activation of the muscles is determined by a number of factors, among which the most important are the reciprocal position of the members of the body and the interaction of the feet with the support. The reflection of the configuration of the body in the system of internal representation also plays an important role.