Human muscle atrophy in supportlessness: effects of short-term exposure to dry immersion.

Atrophy of skeletal muscle is a response that is considered as the most consistent under conditions of real and simulated weightlessness. Microgravity is transformed in the motor system into a number of factors, the most important of them are considered axial unloading and support unloading. The effects of support stimulus may be evaluated in studies under conditions of dry immersion (DI) which provides the equal distribution of the mechanical pressure (e.g. hydrostatic pressure) throughout the surface of the body. Thus the deprivation of the gradient of the mechanical pressure simulates the supportless conditions. The study was aimed to test if the support unloading simulated in dry immersion induces not only functional but also structural alterations in human postural muscles.