During spaceflight, we are exposed to the long-term unloading environment. Although a number of physiological adaptations occurred in our body, these are not necessarily favorable. The loss of skeletal muscle mass is one of the most obvious phenomenons. After only 5 days in space, an 11–24% loss in muscle fiber crosssection is observed (Booth and Criswell 1997). Likewise, muscle disuse through the limb immobilization and prolonged bed rest also represent the large degree of muscle loss (Bloomfield 1997; Droppert 1993). Indeed, 2 weeks of leg immobilization has been shown to result in an almost 5% reduction in quadriceps lean mass and 27% fall in isometric strength (Jones et al. 2004). A 20% reduction in type I muscle fiber cross-sectional area and a 30% reduction in type II fiber area has been observed following 60 days of bed rest (Salanova et al. 2008). However, the mechanisms by which devices mainly transduce these changes are not well understood.
KeywordsUbiquitin Ligase Myosin Heavy Chain Muscle Atrophy Skeletal Muscle Atrophy Limb Immobilization
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