Effects of countermeasure exercise training on cardiovascular fitness and kinetics during spaceflight and in terrestrial analog conditions

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Purpose: Cardiovascular fitness (CVF) is paramount for the Astronauts' safety, mission success, and unassisted planetary landings in future long-term spaceflight. Despite countermeasure exercise (CE) against the degenerating effects of microgravity, limited activity in isolation, and reduced external stimuli (Norsk, 2020), CVF is still reduced after spaceflight (Hoffmann et al., 2016). Terrestrial analogs are utilized for CE optimization, but a comparative analysis considering study design and individual pre-mission fitness level should investigate the recurring discrepancies to spaceflight.
Methods: CVF was assessed pre, at mission day 42 (MD) and post in 60MD of head-down bed rest with horizontal reactive jumps (HDBR;N=22;11Ctrl;30±6y;V'O2peak:46.9±8.8ml×kg×min-1); 30MD isolation with bicycle and strength training (HERA;N=16,40±9y;V'O2peak:38.5±3.9ml×kg×min-1), 120MD isolation with treadmill training (SIRIUS;N=11;34±6y;V'O2peak:37.2±6.8ml×kg×min-1), and 174±22MD onboard the ISS with BD-2-treadmill and strength training (ISS;N=10;44±3y; V'O2peak:36.7±4.5ml×kg×min-1). The exercise test included moderate-intensity pseudo-random work rate changes for HR- and V'O2pulm-kinetics analysis and a ramp protocol for peak values (HRpeak, V'O2peak). ANCOVAs were applied to the factors MD, Study, and pre-mission V'O2peak as a covariate (CoV).
Results: Across all studies, an MD (P=0.06;η²=0.190) and MDXCoV (PV'O2peak was reduced post-mission for HDBR and ISS. In SIRIUS, HRpeak was significantly reduced in-mission while V'O2peak improved with CE-duration (P=0.002). HR-kinetics were slower post-mission for HDBR (P=0.020) and in-flight for ISS at MD44 and MD118 (P=0.043). V'O2-kinetics were slower at MD22 in HERA, MD30 in SIRIUS, and MD118 onboard ISS (all PDiscussion: Pre-mission fitness level and study design influence CE's effects on CVF, which should be considered with more individualized CE in future studies. HR and V'O2-kinetics seem particularly sensitive to changes in CVF, can be derived from submaximal exercise, and extend the available information on CVF.
TitelAmerican Society for Gravitational and Space Research
PublikationsstatusVeröffentlicht - 10.11.2022

ID: 11146927

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