EFFECTS OF UNILATERAL SELECTIVE HYPERGRAVITY STIMULATION ON GAIT

The purpose of this work is to analyse the neural mechanisms of human motor perturbations induced by dynamic changes in gravity. A unilatera l selective hypergravity stimulation (USHS) was produced by stretching an elastic band between the right shoulder and foot. The consequences of the extensor muscle tone change due to the positioning (increased muscular loading) and to its removal (decreased muscular loading) by t he elastic band were observed on motor gait skill. Gait spatio-tempora l parameters (horizontal displacement of both feet) and lower limb fun ctional length variations (efficiency of flexion and extension movemen ts of the lower limbs) were measured. The latter measure was performed using a device specially designed for that purpose. The main results were: (1) during and after USHS, gait perturbations appeared on the le ft-the body side not directly stimulated, (2) just after the end of US HS, perturbations were present on the right (homolateral) side evidenc ing a post treatment effect which caused a decrease in functional shor tening of the lower limb during extension and an increase of functiona l shortening of the lower limb during stance (opposite in sense to the modification observed during swing). Such results afford evidence tha t, in addition to vestibular receptors, the mechanoreceptors of extens or muscles are involved in determining the changes in motor skills obs erved at the beginning and at the end of space flights.