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Isokinetic Strength Changes Following Long-Duration Spaceflight on the ISS
Kirk L English1, Stuart M C Lee, James A Loehr
1JES Tech; Wyle Science, Technology, and Engineering Group, TX, USA.
Aerospace Medicine and Human Performance
|December 3, 2015
Summary
Long spaceflights decrease muscle strength, but exercise countermeasures help. Strength largely recovers within 30 days of returning to Earth, though some deficits may persist.
Area of Science:
- Space physiology
- Human adaptation to microgravity
- Exercise countermeasures
Background:
- Long-duration spaceflight leads to significant muscle strength loss.
- This loss poses risks for astronaut operations, emergency egress, and future exploration.
- Isokinetic testing is crucial for quantifying strength changes and evaluating exercise effectiveness.
Purpose of the Study:
- To evaluate changes in isokinetic strength after long-duration spaceflight.
- To identify factors modifying spaceflight-induced strength loss, including gender, exercise hardware, and preflight strength.
- To assess the effectiveness of in-flight exercise in mitigating strength decline.
Main Methods:
- Retrospective analysis of isokinetic strength data from 37 International Space Station (ISS) crewmembers.
- Evaluation of strength changes following 163 ± 38 days of spaceflight.
- Statistical examination of gender, resistance exercise hardware (iRED vs. ARED), and preflight strength as potential moderators.
Main Results:
- Mean isokinetic strength decreased by 8-17% post-spaceflight.
- Strength improved within 30 days of return, with 1-9% deficits persisting.
- No significant gender differences in strength loss were observed.
- Crewmembers using the Advanced Resistive Exercise Device (ARED) showed potentially smaller strength losses compared to the interim Resistive Exercise Device (iRED).
Conclusions:
- In-flight resistance exercise did not fully prevent strength loss but may be optimized with advanced devices like ARED.
- Strength is largely recovered within 30 days post-flight with reconditioning.
- Preflight strength levels are moderately correlated with postflight strength changes.
