[Effect of long-term hypergravitation on the skeletal-muscular tissue in rats].

The space flight or simulated gravitational unloading lead to the muscle atrophy, slow-to-fast transformation of muscle fibers and myofibrillar damages both in humans and animals (1, 7, 13, 17). This process could be prevented by the exercise training during space flight (1), (partly) by periodic weight support during unloading (13). It has been demonstrated in these studies that there is some level of force production necessary for the maintenance of skeletal muscle properties. It is known that adaptation to the physical training frequently induces augmentation in cross-sectional area (CSA) of muscle fibers (MF), transformation of fibers, augmentation of mitochondrial volume density, and increase in absolute volume of myofibrillas. Numerous observations suggest importance of gravitational loading in regulating muscle mass. The centrifuging is believed to be useful for preventing muscle functional and structural losses under microgravity. But there are few studies designed to investigate effect of artificial gravity on the skeletal musculature (2, 7). Our objective was to investigate structural adaptation in slow-twitch soleus muscle (percentage of connective tissue and central nuclei, fiber size, myosin heavy chain isotope, myofibrillar proteins and mitochondria volume density) after 19 and 33 days of hypergravity.