Postural Equilibrium Following Exposure to Weightless Space Flight

Abstract

Postural equilibrium performance by the Skylab 1/2, 3 and 4 crewmen following exposure to weightlessness of 28, 59 and 84 days, respectively, was evaluated using a modified version of a quantitative ataxia test developed by Graybiel and Fregly. Performance for this test was measured under 2 sets of conditions. In the 1st test the crewman was required to maintain postural equilibrium on narrow metal rails (or floor) with his eyes open. In the 2nd condition, he attempted to balance with his eyes closed. A comparison of preflight and postflight data indicated moderate postflight decrements in postural equilibrium in 3 of the crewmen during the eyes open test condition. In the eyes closed condition, a considerable decrease in ability to maintain balance on the rails was observed postflight for all crewmen tested. Magnitude of change was most pronounced during the 1st postflight test day. Improvement was slow; recovery of preflight baseline levels of performance was evidently complete at the end of approximately 2 wk for all crewmen. Findings are explained in terms of functional alterations in the kinesthetic, touch, vestibular and neuromuscular sensory mechanisms induced by prolonged absence of a normal 1-g gravitational environment.