Short-arm centrifugation as a partially effective musculoskeletal countermeasure during 5-day head-down tilt bed rest-results from the BRAG1 study.

Purpose: Human centrifugation, also called artificial gravity (AG), is proposed as a combined strategy against detrimental effects of microgravity in long-term space missions. This study scrutinized human short-arm centrifugation as countermeasure against musculoskeletal de-conditioning. Method: Eleven healthy male subjects [mean age of 34 (SD 7) years] completed the cross-over trial, including three campaigns of −6° head-down tilt bed rest (HDT) for 5 days, with preceding baseline data collection and recovery phases. Bed rest without AG was used as control condition (Ctrl), and AG with 1 g at the center of mass applied once per day for 30 min in one bout (AG) and in 6 bouts of 5 min (AG, 3-min rest between bouts) as experimental conditions. End-points were muscle strength, vertical jump performance, and biomarkers of bone and protein metabolism. Result: AG was better tolerated than AG. Bone resorption markers CTX, NTX, and DPD all increased by approximately 25 % toward the end of bed rest ( P < 0.001), and nitrogen balance decreased by approximately 3 g/day ( P < 0.001), without any protection by AG ( P > 0.4). Decreases in vertical jump height by 2.1 (SE 0.6) cm after Ctrl bed rest was prevented by either of the AG protocols ( P = 0.039). Conclusion: The present study yielded succinct catabolic effects upon muscle and bone metabolism that were un-prevented by AG. The preservation of vertical jump performance by AG in this study is likely caused by central nervous rather than by peripheral musculoskeletal effects. [ABSTRACT FROM AUTHOR]