The launching of the shuttle in 1981 initiated a new era in the space age. In spite of the more than 20 yr of experience and research on the anatomical and physiological effects of weightlessness, problems remain. The resolution of these problems requires countermeasures, of which exercise deserves to be considered. The uncertainty concerning the importance of exercise has evolved, in part, because of the limited number of subjects studied, the paucity of controlled experimental designs, the inability to follow standardized routines in a space environment, and the lack of specificity in the exercises prescribed. Exercise has the potential to be an effective countermeasure for the decreases in bone density, fluid volumes, muscle mass, muscular strength, orthostatic tolerance, cardiovascular deconditioning, and submaximal exercise performances that occur in a 0-gravity environment if aerobic training is minimized, maximum isometric and power-type exercises are emphasized, and circuit-training principles utilized. Because the majority of future space flights will last 21 d or less, the majority of future studies on the role of exercise should concentrate on that time period.
©1983The American College of Sports Medicine