OBJECTIVES:
Crewmembers continue to experience muscle atrophy after space flight, particularly from long-duration missions on the International Space Station (ISS), which results in higher risk for injury upon their return to Earth. More robust exercise equipment is arriving on the ISS and new exercise prescriptions are planned to counteract the muscle losses. With these new exercise countermeasures; however, there currently are no methods to monitor muscle status in flight to assist in determining the efficacy of these countermeasures. Given that medical imaging with ultrasound is available on the ISS, it is feasible that ultrasound scanning could be performed before, during, and after space flight to assess muscle size changes. This ground-based pilot study evaluated and validated a technique of using ultrasound to measure leg muscle cross sectional area (CSA) and volume. These ultrasound measures were also compared with a magnetic resonance image (MRI) of the leg to determine the accuracy and repeatability of the ultrasound muscle measurements. This pilot study is part of the larger Integrated Resistive and Aerobic Training Study (SPRINT) conducted on the ISS. Ultrasound will ultimately be used to assess the effectiveness of the SPRINT exercise prescription on ISS crewmembers using the Advanced Resistive Exercise Device (ARED) and the second generation treadmill (T2) during their missions. This ultrasound technique could also be applicable for evaluating future exercise countermeasures both on ISS and Constellation missions.

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