[State of skeletal muscle fibers in rats during physical exercise after anti-orthostatic tail suspension in modeling the weightlessness].

The state of myofibers of types I, IIA and IIB of biceps femoris m. of Wistar rats exposed to tail suspension for 14 or 21 days was investigated after they experienced a 15-minute locomotor load: running on a treadmill or hindlimb stretching. In all types of myofibers both exposures prevented the development of most structural and metabolic changes that occurred in response to suspension simulating the physiological effects of weightlessness. The distribution and level of variations of muscle parameters depended on the kind of exposure and type of myofibers.