Time course of change in soleus muscle fibers of rats subjected to chronic centrifugation.

Soleus muscles from three groups of rats were analysed for changes in muscle fiber populations and diameters after being subjected to chronic centrifugation. The experimental groups were: earth control, raised at earth gravity with no rotation; rotation control, subjected to a gravitational force of 1.03 g and 30 rpm; and rotation experimental, subjected to a gravitational force of 2 g and 30 rpm. One male and one female of each group were killed at 7, 14, 21, 35, 42, 45, 49, 56 and 60 d after initiation of the experiment. Hypergravity resulted in an increase in the proportion of slow oxidative fibers. The time course of change in their muscle fiber populations is plotted. The time course of change in the ratio of body weight to muscle fiber diameter in the rotation control animals differed from that of the earth control and rotation experimental animals.