[Morphological study of the muscle fibers and the microcirculatory bed of the muscles in monkeys during head-down tilt hypokinesia].

Primates were exposed to head-down tilt for 7 and 12 days. As the study continued, the body mass and muscle mass decreased, muscles became atrophic, and the number of functioning capillaries lessened. Out of the three muscles examined (gastrocnemius, soleus, and biceps brachii), the soleus muscle showed the greatest changes. It can be concluded that, in spite of blood redistribution and blood pooling in the upper body (seen during autopsy), no blood displacement occurs in the microcirculatory bed. The decrease in the number of functioning capillaries is normally regarded as a change that is concomitant with muscle atrophy.