Effect of resistive exercise combined with vibration on body composition and energy balance – Results from the 21-day MNX bedrest study

High volume exercise is crucial in preventing spaceflight-induced muscle atrophy but can induce reductions in body mass and fat mass, due to a mismatch between energy intake and total energy expenditure (TEE). This randomized cross-over trial investigated whether short-duration resistive-vibration exercise (RVE) prevents muscle loss without inducing negative energy balance during a medium-duration bedrest (IDRCB n°2012-A00337-36). Twelve healthy young males underwent a 21-day bedrest with RVE or without (CNT) in a randomized cross-over trial, each trial being separated by at least 120 days. Subjects could leave unfinished the meals designed to match their estimated TEE. TEE was assessed using doubly labelled water and energy balance from dual X-ray absorptiometry-generated body composition changes. Compared to strict bedrest, RVE limited by 25 % the bedrest-induced loss in body mass (P < 0.07) and lean body mass (P = 0.12), without reaching significance, and partially lessened the decline in overall muscle function and aerobic capacity. RVE reduced resting metabolic rate decrease (P = 0.03) without increasing activity energy expenditure and TEE. Both groups adjusted their energy intake to match the reductions in TEE, resulting in equilibrated energy balance. RVE may offer some benefits in mitigating muscle mass and function decline under microgravity conditions, without affecting energy balance and fat mass. • Exercise is the cornerstone of countermeasure programs for space exploration. • High volumes of exercise were, however, reported to induce negative energy balance during spaceflights, which can alter an astronaut's health. • In this bedrest study, a new countermeasure combining resistive exercise and vibration was tested under simulated microgravity conditions. • This low-volume RVE countermeasure only partially preserved muscle mass and function without impacting energy balance.