BackgroundTo counteract microgravity (µG)-induced adaptation, European Space Agency (ESA) astronauts on long-duration missions (LDMs) to the International Space Station (ISS) perform a daily physical exercise countermeasure program. Since the first ESA crewmember completed an LDM in 2006, the ESA countermeasure program has strived to provide efficient protection against decreases in body mass, muscle strength, bone mass, and aerobic capacity within the operational constraints of the ISS environment and the changing availability of on-board exercise devices. The purpose of this paper is to provide a description of ESA’s individualised approach to in-flight exercise countermeasures and an up-to-date picture of how exercise is used to counteract physiological changes resulting from µG-induced adaptation. Changes in the absolute workload for resistive exercise, treadmill running and cycle ergometry throughout ESA’s eight LDMs are also presented, and aspects of pre-flight physical preparation and post-flight reconditioning outlined.ResultsWith the introduction of the advanced resistive exercise device (ARED) in 2009, the relative contribution of resistance exercise to total in-flight exercise increased (33–46 %), whilst treadmill running (42–33 %) and cycle ergometry (26–20 %) decreased. All eight ESA crewmembers increased their in-flight absolute workload during their LDMs for resistance exercise and treadmill running (running speed and vertical loading through the harness), while cycle ergometer workload was unchanged across missions.ConclusionIncreased or unchanged absolute exercise workloads in-flight would appear contradictory to typical post-flight reductions in muscle mass and strength, and cardiovascular capacity following LDMs. However, increased absolute in-flight workloads are not directly linked to changes in exercise capacity as they likely also reflect the planned, conservative loading early in the mission to allow adaption to µG exercise, including personal comfort issues with novel exercise hardware (e.g. the treadmill harness). Inconsistency in hardware and individualised support concepts across time limit the comparability of results from different crewmembers, and questions regarding the difference between cycling and running in µG versus identical exercise here on Earth, and other factors that might influence in-flight exercise performance, still require further investigation.

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Background: Recommendations on resistance training (RT) set-volume protocols in preparation for spaceflight muscular strength conditioning remains equivocal. A meta-analysis was performed on the effects of single-set (S), or three-set (M3) RT on muscular strength per exercise for different body segments and joint types (multi-joint and single-joint). Methods: Computerized searches were performed on PubMed, MEDLINE and SPORTDiscus™. Twelve studies were considered appropriate according to pre-set eligibility criteria. Outcomes analyzed were pre-to-post-muscular strength change on; multi-joint and single-joint combined; upper body only; lower body only; multi-joint exercises only; single-joint exercises only. Results: Upper body exercise analysis on combined subjects and untrained subjects only reported greater but not significant strength gains with M3 (ES 0.37; 95% CI 0.09–0.82; P = 0.11 and ES 0.35; 95% CI−0.49 to 1.19; P = 0.42). Trained only subjects reported superior strength gains with M3 (ES 0.63; 95% CI 0.34–0.92; P = <0.0001). Lower body exercise on combined subjects and untrained subjects only reported superior strength gains with M3 (ES 0.35; 95% CI 0.10–0.60; P = 0.006 and ES 0.49; 95% CI 0.14–0.83; P = 0.005). Trained subjects only observed greater but not significant strength gains with M3 (ES 0.18; 95% CI −0.23 to 0.58; P = 0.39). Multi-joint exercise on combined subjects reported greater strength gains with M3 (ES 0.83; 95% CI 0.14–1.51; P = 0.02). Trained only subjects reported greater strength gains with M3 (ES 0.52; 95% CI 0.10–0.94; P = 0.02). Single-joint exercise on combined subjects and untrained only observed greater strength gains for M3 (ES 0.49; 95% CI 0.26–0.72; P = <0.0001 and ES 0.56; 95% CI 0.21–0.91; P = 0.002). Trained only subjects reported greater but not significant strength gains with M3 (ES 0.37; 95% CI −0.01 to 0.75; P = 0.06). Conclusion: For astronauts in space-flight preparation, the findings suggest that M3 training appears to be preferable over S for developing muscular strength. Nevertheless, depending on the physical conditioning of the crew member or tight pre-flight scheduling, S is still able to provide a positive strength training stimulus.