Evidence for a load receptor contribution to the control of posture and locomotion.

A basic aspect of the neuronal control of bipedal stance and gait represents the antigravity function of leg extensors. Proprioceptive reflexes involved in the maintenance of body equilibrium depend on the presence of contact forces opposing gravity. Extensor load receptors are thought to signal changes of the projection of the body's centre of mass with respect to the feet. According to recent observations in the spinal cat, this afferent input probably arises from Golgi tendon organs and represents a newly discovered function of these receptors in the regulation of stance and gait. In humans, evidence for a significant contribution of the load receptor to leg muscle activation has come from immersion experiments. Compensatory leg muscle activation depends on the actual body weight. Furthermore, recent experiments in paraplegic patients showed that the beneficial effects of a locomotor training critically depends on the initial degree of body unloading and reloading during the course of the training period.