School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK.
J Cachexia Sarcopenia Muscle. 2021 Feb;12(1):52-69. doi: 10.1002/jcsm.12661. Epub 2020 Dec 21.
Poor recovery from periods of disuse accelerates age-related muscle loss, predisposing individuals to the development of secondary adverse health outcomes. Exercise prior to disuse (prehabilitation) may prevent muscle deterioration during subsequent unloading. The present study aimed to investigate the effect of short-term resistance exercise training (RET) prehabilitation on muscle morphology and regulatory mechanisms during 5 days of bed rest in older men.
Ten healthy older men aged 65-80 years underwent four bouts of high-volume unilateral leg RET over 7 days prior to 5 days of inpatient bed rest. Physical activity and step-count were monitored over the course of RET prehabilitation and bed rest, whilst dietary intake was recorded throughout. Prior to and following bed rest, quadriceps cross-sectional area (CSA), and hormone/lipid profiles were determined. Serial muscle biopsies and dual-stable isotope tracers were used to determine integrated myofibrillar protein synthesis (iMyoPS) over RET prehabilitation and bed rest phases, and acute postabsorptive and postprandial myofibrillar protein synthesis (aMyoPS) rates at the end of bed rest.
During bed rest, daily step-count and light and moderate physical activity time decreased, whilst sedentary time increased when compared with habitual levels (P < 0.001 for all). Dietary protein and fibre intake during bed rest were lower than habitual values (P < 0.01 for both). iMyoPS rates were significantly greater in the exercised leg (EX) compared with the non-exercised control leg (CTL) over prehabilitation (1.76 ± 0.37%/day vs. 1.36 ± 0.18%/day, respectively; P = 0.007). iMyoPS rates decreased similarly in EX and CTL during bed rest (CTL, 1.07 ± 0.22%/day; EX, 1.30 ± 0.38%/day; P = 0.037 and 0.002, respectively). Postprandial aMyoPS rates increased above postabsorptive values in EX only (P = 0.018), with no difference in delta postprandial aMyoPS stimulation between legs. Quadriceps CSA at 40%, 60%, and 80% of muscle length decreased significantly in EX and CTL over bed rest (0.69%, 3.5%, and 2.8%, respectively; P < 0.01 for all), with no differences between legs. No differences in fibre-type CSA were observed between legs or with bed rest. Plasma insulin and serum lipids did not change with bed rest.
Short-term resistance exercise prehabilitation augmented iMyoPS rates in older men but did not offset the relative decline in iMyoPS and muscle mass during bed rest.
恢复期的不良表现会加速与年龄相关的肌肉损失，使个体易发生继发性不良健康后果。在停用前进行运动（预康复）可能会防止随后的卸载过程中肌肉恶化。本研究旨在探讨短期抗阻运动训练（RET）预康复对老年人 5 天卧床休息期间肌肉形态和调节机制的影响。
10 名年龄在 65-80 岁的健康老年人在 5 天住院卧床休息前的 7 天内进行了 4 次大容量单侧腿部 RET。在 RET 预康复和卧床休息期间监测身体活动和步数，同时记录整个过程中的饮食摄入。在卧床休息前后，测定股四头肌横截面积（CSA）和激素/脂质谱。连续肌肉活检和双稳定同位素示踪剂用于确定 RET 预康复和卧床休息期间的整体肌纤维蛋白合成（iMyoPS），以及卧床休息结束时的急性餐后和餐后肌纤维蛋白合成（aMyoPS）率。
卧床休息期间，与习惯性水平相比，每日步数和轻、中度体力活动时间减少，而久坐时间增加（所有 P<0.001）。卧床休息期间的蛋白质和膳食纤维摄入量低于习惯性值（均 P<0.01）。在预康复期间，与非运动对照组相比，运动侧（EX）的 iMyoPS 率明显更高（1.76±0.37%/天比 1.36±0.18%/天，P=0.007）。在卧床休息期间，EX 和 CTL 侧的 iMyoPS 率相似下降（CTL，1.07±0.22%/天；EX，1.30±0.38%/天；P=0.037 和 0.002，分别）。只有在 EX 中，餐后 aMyoPS 率高于餐后吸收值（P=0.018），但双腿之间的餐后 aMyoPS 刺激差异无统计学意义。卧床休息期间，EX 和 CTL 侧的股四头肌 CSA 在 40%、60%和 80%肌肉长度处均显著下降（分别为 0.69%、3.5%和 2.8%；均 P<0.01），双腿之间无差异。双腿之间或卧床休息期间，纤维类型 CSA 无差异。血浆胰岛素和血清脂质在卧床休息期间没有变化。
短期抗阻运动预康复可提高老年人的 iMyoPS 率，但不能抵消卧床休息期间 iMyoPS 和肌肉质量的相对下降。
