Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX.
Universities Space Research Association, Houston, TX.
Med Sci Sports Exerc. 2018 Sep;50(9):1929-1939. doi: 10.1249/MSS.0000000000001616.
Prolonged confinement to head-down bed rest (HDBR) results in musculoskeletal losses similar to those observed during long-duration space flight. Exercise countermeasures by themselves have not completely prevented the deleterious losses in muscle mass or function in HDBR or space flight.
The objective was to investigate the safety and efficacy of intermittent, low-dose testosterone treatment in conjunction with NASA exercise (SPRINT) countermeasures during 70 d of 6° HDBR.
Healthy men (35 ± 8 yr) were randomized into one of three groups that remained inactive (CON) or performed exercise 6 d·wk in addition to receiving either placebo (PEX) or testosterone treatment (TEX, 100 mg·wk). Testosterone/placebo injections were administered once a week for 2 wk, followed by 2 wk off and so on, during HDBR.
Total, leg, and trunk lean body mass (LBM) consistently decreased in CON, increased in TEX, and had little or no changes in PEX. Total, leg, and trunk fat mass consistently increased in CON and PEX and decreased in TEX. Leg strength decreased in CON, whereas PEX and TEX were protected against loss in strength. Changes in leg LBM correlated positively with changes in leg muscle strength.
Addition of a testosterone countermeasure enhanced the preventative actions of exercise against body composition changes during long-term HDBR in healthy eugonadal men. This is the first report to demonstrate that cycled, low-dose testosterone treatment increases LBM under conditions of strict exercise control. These results are clinically relevant to the development of safe and effective therapies against muscle atrophy during long-term bed rest, aging, and disease where loss of muscle mass and strength is a risk. The potential space flight applications of such countermeasure combinations deserve further investigations.
长时间的头低位卧床（HDBR）会导致类似于长时间太空飞行中观察到的肌肉骨骼损失。单独的运动锻炼措施并不能完全防止 HDBR 或太空飞行中肌肉质量或功能的有害损失。
本研究旨在探讨间歇、低剂量睾酮治疗与 NASA 运动（SPRINT）措施联合应用于 6°头低位卧床 70 天的安全性和有效性。
健康男性（35±8 岁）随机分为三组：不活动组（CON）或在接受安慰剂（PEX）或睾酮治疗（TEX，100mg·wk）的基础上进行运动锻炼，每组 6 天/周。HDBR 期间，每周进行一次睾酮/安慰剂注射，持续 2 周，然后停药 2 周，以此类推。
CON 组的总体、腿部和躯干瘦体重（LBM）持续下降，TEX 组增加，PEX 组变化不大或略有增加。CON 和 PEX 组的总体、腿部和躯干脂肪量持续增加，而 TEX 组则减少。CON 组的腿部力量下降，而 PEX 和 TEX 组则可防止力量下降。腿部 LBM 的变化与腿部肌肉力量的变化呈正相关。
睾酮措施的加入增强了运动对健康正氮平衡男性长期 HDBR 期间身体成分变化的预防作用。这是首次报道表明，周期性、低剂量睾酮治疗可在严格运动控制条件下增加 LBM。这些结果与开发针对长期卧床、衰老和疾病期间肌肉萎缩的安全有效的治疗方法具有临床相关性，在这些情况下，肌肉质量和力量的损失是一个风险。这种对策组合的潜在太空飞行应用值得进一步研究。
