Lean Tissue Mass and Muscle Strength

Abstract

1833 INRODUCTION: Exercise countermeasures during long duration space flight have historically employed treadmill and cycle exercises with little or no resistive component. On the Russian Mir Space Station, crewmembers performed resistive exercise with bungee cords (max resistance: 40 kg). An interim resistive exercise device (iRED; max resistance: 135 kg) was deployed for use by crewmembers on the International Space Station (ISS) to compliment aerobic exercise. Due to operational and hardware constraints, the iRED has not been used to the extent originally planned. The purpose of this project was to compare lean tissue mass and isokinetic strength results from Mir (when low intensity resistive exercise was performed) with recent data from ISS crews. METHODS: Whole body lean mass (WBLM; kg), leg lean mass (LLM; kg), and isokinetic knee extensor (KE) and flexor (KF) peak torque (PkT; N-m) were measured in 5 Mir and 9 ISS U.S. crewmembers. Measurements were obtained at approximately 180 d and 30 d before launch and 6–8 d after landing. Baseline was accepted as the mean of pre-flight values. Statistical analyses were completed using a 2-way repeated measures ANOVA in which time (repeated) and group (Mir vs. ISS) were main effects (*P<0.05, different from pre-flight). RESULTS: There was a main effect of space flight on WBLM (−3 ± 1%). Post-flight LLM was reduced in both Mir (− 7 ± 2%) and ISS (−4 ± 2%) crews. Similarly, KE and KF PkT were reduced in both groups post-flight. There were no statistical differences between Mir and ISS crewmembers in lean tissue mass or isokinetic muscle strength.TableCONCLUSION: These results suggest that to date the iRED in its current configuration (and availability) has not provided additional protection to lean tissue and muscle strength during long-duration space flight.