Physical Training for Long-Duration Spaceflight.

INTRODUCTION: Physical training has been conducted on the International Space Station (ISS) for the past 10 yr as a countermeasure to physiological deconditioning during spaceflight. Each member space agency has developed its own approach to creating and implementing physical training protocols for their astronauts. We have divided physical training into three distinct phases (preflight, in-flight, and postflight) and provided a description of each phase with its constraints and limitations. We also discuss how each member agency (NASA, ESA, CSA, and JAXA) prescribed physical training for their crewmembers during the first 10 yr of ISS operations. It is important to understand the operational environment, the agency responsible for the physical training program, and the constraints and limitations associated with spaceflight to accurately design and implement exercise training or interpret the exercise data collected on ISS. As exploration missions move forward, resolving agency differences in physical training programs will become important to maximizing the effectiveness of exercise as a countermeasure and minimizing any mission impacts.

Human adductor muscles atrophy after short duration of unweighting.

The purpose of this study was to investigate the effect of 20 days of bed rest (BR) on the physiological cross-sectional area (PCSA) of the adductor (AD) muscle group. Five healthy men and five healthy women were kept on a horizontal bed for 20 days. To calculate the PCSA of the AD muscle group, transaxial magnetic resonance imaging of the right thigh was acquired four times for each of the subjects: (1) pre BR, (2) on the tenth day of BR, (3) post BR, and (4) 1 month after BR. Overall, the PCSA measurements of the AD muscle group and its individual muscles were significantly decreased on the tenth day of BR and at post BR; however, they had recovered to the baseline within 1 month of the reambulation period. The amount and pattern of relative change in the PCSA measurements of the AD muscle group were similar to those of the knee extensor (KE) and knee flexor (KF) muscle groups studied previously. These results suggested that the AD muscle group showed an atrophic response that was similar to the KE and KF muscle groups after unweighting; therefore, we should pay much more attention to the AD muscle group when considering countermeasures for future human spaceflight projects.