Development of and adherence to artificial gravity and resistive vibration exercises during 60 days of hypoxic 6° head-down tilt bed rest: BRAVE study.

Artificial gravity (AG) combined with resistive vibration exercise has been proposed as a multi-system countermeasure for long-duration spaceflight; however, its operational feasibility during prolonged unloading remains insufficiently characterised. This study primarily evaluated the feasibility, tolerability, and adherence to a structured resistive vibration exercise protocol delivered either under artificial gravity (AGRVE) or in horizontal loading (HRVE) during 60 days of hypoxic ( F I O 2 ${{F}_{{\mathrm{I}}{{{\mathrm{O}}}_2}}}$  = 0.14) 6° head-down tilt bed rest. Secondary observations included delayed-onset muscle soreness (DOMS) and changes in eight-repetition maximum strength (8RM) to inform load progression. Sixteen healthy male participants were allocated to HRVE (n = 9) or AGRVE (n = 8) and completed near-daily 30-min training sessions at light (30% 1RM) and moderate (50% 1RM) intensities. Adherence was high in both groups (HRVE: 98.5%; AGRVE: 96.3%). In AGRVE, early-session interruptions were primarily due to motion sickness or presyncopal symptoms; motion sickness severity declined significantly across repeated centrifugation exposures (P < 0.001), consistent with vestibular habituation. HRVE interruptions were predominantly fatigue-related. DOMS remained low throughout the intervention (typically 0-3/10). 8RM increased over time in both groups (P < 0.001). Progressive resistive vibration exercise can be implemented with high adherence during prolonged hypoxic bed rest, including when combined with AG. Motion sickness represents the principal early operational constraint specific to squat-based AG exposure but diminishes with repeated sessions.