ABSTRACT
In hibernating big brown bats, pectoral muscles demonstrated significant atrophy, but since body mass decreased as well, the pectoral mass remained a constant fraction of body mass. Despite differences in the paradigms used in the aforementioned studies, locomotor muscles atrophy and oxidative capacity increases. When physical activity is reduced there is a concomitant reduction in the capacity for muscle function. If muscles of hibernators were to lose mass and aerobic capacity during the hibernation period, then locomotor function upon spring arousal would be compromised. Additionally, since muscle contraction is important in the production of heat, reduction in mass and enzymatic capacity could compromise thermogenesis as well. In addition to the more traditional models of disuse/detraining utilizing humans and rats, there are a number of studies which have examined muscle in animals that undergo natural periods of inactivity, such as hibernation. No changes were observed in cardiac mass, but both skeletal muscles were atrophied after 90 days in hibernation.
