Abstract
PurposeSpace agencies are looking for effective and efficient countermeasures for the degrading effects of weightlessness on the human body. The aim of this study was to assess the effects of a novel jump exercise countermeasure during bed rest on vitals, body mass, body composition, and jump performance.Methods23 male participants (29±6 years, 181±6 cm, 77±7 kg) were confined to a bed rest facility for 90 days: a 15-day ambulatory measurement phase, a 60-day six-degree head-down-tilt bed rest phase (HDT), and a 15-day ambulatory recovery phase. Participants were randomly allocated to the jump training group (JUMP, n = 12) or the control group (CTRL, n = 11). A typical training session consisted of 4x10 countermovement jumps and 2x10 hops in a sledge jump system. The training group had to complete 5–6 sessions per week.ResultsPeak force for the reactive hops (3.6±0.4 kN) as well as jump height (35±4 cm) and peak power (3.1±0.2 kW) for the countermovement jumps could be maintained over the 60 days of HDT. Lean body mass decreased in CTRL but not in JUMP (-1.6±1.9 kg and 0±1.0 kg, respectively, interaction effect p = 0.03). Resting heart rate during recovery was significantly increased for CTRL but not for JUMP (interaction effect p<0.001).ConclusionParticipants tolerated the near-daily high-intensity jump training and maintained high peak forces and high power output during 60 days of bed rest. The countermeasure was effective in preserving lean body mass and partly preventing cardiac deconditioning with only several minutes of training per day.
Highlights
To maintain crew health during long-term space missions, adequate countermeasures are necessary
Peak force for the reactive hops (3.6±0.4 kN) as well as jump height (35±4 cm) and peak power (3.1±0.2 kW) for the countermovement jumps could be maintained over the 60 days of head-down-tilt bed rest phase (HDT)
Lean body mass decreased in CTRL but not in JUMP (-1.6±1.9 kg and 0±1.0 kg, respectively, interaction effect p = 0.03)
Summary
To maintain crew health during long-term space missions, adequate countermeasures are necessary. An exercise-based countermeasure should preserve the integrity and function of bones, neuromuscular and cardiovascular system. The countermeasure should be efficient, requiring a minimum of crew time. Astronauts on board the International Space Station are required to exercise for two to two and a half hours per day [1] using three different countermeasure systems (treadmill, cycle ergometer and the advanced resistive exercise device ARED), but even this time-consuming training is not successful in fully maintaining muscle and bone mass and function [1, 2]. Space agencies are highly interested in more effective and efficient integrated countermeasures. Jump training has repeatedly been shown to increase leg muscle strength [6] and is associated with increased lean mass [7]
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