Evidence of effective cardiovascular countermeasures during spaceflights: insights from wearable monitoring.

Microgravity induces profound cardiovascular changes, prompting space agencies to develop countermeasures to preserve their crewmembers' health. This study aimed to use a portable device based on electro-, impedance- and seismo-cardiography, to monitor a series of cardiovascular features in 17 cosmonauts. Our results showed that the evolution of cardiac time intervals, blood pressure, stroke volume, and cardiac systolic kinetic energy depended on the chosen baseline position. After five months in space, heart rate increased compared to the supine baseline on Earth (p = 0.013, d = 0.86) but not to the sitting position. Similarly, a marker of cardiac contractility (PEP/LVET ratio) decreased relative to the sitting baseline (p = 0.004, d = 1.09) but not the supine reference. All measured features, except heart rate, returned to baseline within three days post-landing. These findings support the efficacy of current countermeasures in facilitating rapid cardiovascular re-adaptation to terrestrial gravity.