Regional muscle loss after short duration spaceflight

Background: Muscle strength and limb girth measurements during Skylab and Apollo missions suggested that loss of muscle mass may occur as a result of spaceflight. Extended duration spaceflight is important for the economical and practical use of space. The loss of muscle mass during spaceflight is a medical concern for long duration flights to the planets or extended stays aboard space stations. Understanding the extent and temporal relationships of muscle loss is important for the development of effective spaceflight countermeasures. Hypothesis: We hypothesized that significant and measurable changes in muscle volume would occur in Shuttle crewmembers following 8 d of weightlessness. Methods: MRI was used to obtain the muscle volumes of the calf, thigh and lower back before and after the STS-47 Shuttle mission. Results: Statistical analyses demonstrated that the soleus-gastrocnemius (- 6.3%), anterior calf (-3.9%), hamstrings (-8.3%), quadriceps (-6.0%) and intrinsic back (-10.3%) muscles were decreased, p < 0.05, compared to baseline, 24 h after landing. At 2 weeks post recovery, the hamstrings and intrinsic lower back muscles were still below baseline, p < 0.05. Conclusions: These results demonstrate that even short duration space-flight can result in significant muscle atrophy.