Posture control after prolonged exercise.

The perturbations of equilibrium after prolonged exercise were investigated by dynamic posturography on nine well-trained subjects (four athletes and five triathletes). A sensory organization test, where the platform and visual surround were either stable or referenced to the subject's sway with eyes open or closed, was performed before and after a 25-km run (average time 1 h 44 min) by the nine subjects. In addition, the same test was performed on the five triathletes only, before and after ergocycle exercise of identical duration (i.e. ergocycle time = running time). The results showed that the ability to maintain postural stability during conflicting sensory conditions decreased after exercise, with some differences depending on the kind of exercise. Sensory analysis revealed that the subjects made less effective use of vestibular inputs after running than after cycling (P < 0.05). Adaptation to prolonged stimulation of proprioceptive, vestibular and visual inputs had probably occurred in the integrating centres during exercise. This adaptation was maintained during the recovery period and could explain the postexercise balance disorders. Other mechanisms such as impairment of motor efferents or haemodynamic changes should not be excluded.