Bird Stephen P, Tarpenning Kyle M, Marino Frank E
School of Human Movement Studies, Charles Sturt University, Bathurst, NSW 2795, Australia.
Metabolism. 2006 May;55(5):570-7. doi: 10.1016/j.metabol.2005.11.011.
A number of physiological events including the level of contractile activity, nutrient status, and hormonal action influence the magnitude of exercise-induced skeletal muscle growth. However, it is not the independent action of a single mechanism, but the complex interaction between events that enhance the long-term adaptations to resistance training. The purpose of the present investigation was to examine the influence of liquid carbohydrate (CHO) and essential amino acid (EAA) ingestion during resistance exercise and modification of the immediate hormonal response on myofibrillar protein degradation as assessed by 3-methylhistidine (3-MH) excretion. After a 4-hour fast, 32 untrained young men (18-29 years) performed a single bout of resistance exercise (complete body; 3 setsx10 repetitions at 75% of 1-repetition maximum; 1-minute rest between sets), during which they consumed a 6% CHO (n=8) solution, a 6-g EAA (n=8) mixture, a combined CHO+EAA (n=8) supplement, or placebo (PLA; n=8) beverage. Resistance exercise performed in conjunction with CHO and CHO+EAA ingestion resulted in significantly elevated (P<.001) glucose and insulin concentrations above baseline, whereas EAA ingestion only increased the postexercise insulin response (P<.05). Time matched at 60 minutes, the PLA group exhibited a peak cortisol increase of 105% (P<.001) with no significant change in glucose or insulin concentrations. Conversely, the CHO and CHO+EAA groups displayed a decrease in cortisol levels of 11% and 7%, respectively. Coinciding with these hormonal response patterns were significant differences in myofibrillar protein degradation. Ingestion of the EAA and CHO treatments attenuated 3-MH excretion 48 hours after the exercise bout. Moreover, this response was synergistically potentiated when the 2 treatments were combined, with CHO+EAA ingestion resulting in a 27% reduction (P<.01) in 3-MH excretion. In contrast, the PLA group displayed a 56% increase (P<.01) in 3-MH excretion. These data demonstrate that not only does CHO and EAA ingestion during the exercise bout suppress exercise-induced cortisol release; the stimulatory effect of resistance exercise on myofibrillar protein degradation can be attenuated, most dramatically when the treatments are combined (CHO+EAA). Through an "anticatabolic effect," this altered balance may better favor the conservation of myofibrillar protein.
许多生理事件，包括收缩活动水平、营养状况和激素作用，都会影响运动诱导的骨骼肌生长程度。然而，增强对阻力训练的长期适应性的并非单一机制的独立作用，而是这些事件之间的复杂相互作用。本研究的目的是，通过检测3 - 甲基组氨酸（3 - MH）排泄量，来研究抗阻运动期间摄入液态碳水化合物（CHO）和必需氨基酸（EAA）以及改变即时激素反应对肌原纤维蛋白降解的影响。在禁食4小时后，32名未经训练的年轻男性（18 - 29岁）进行了一轮抗阻运动（全身运动；3组，每组10次重复，强度为1次最大重复量的75%；组间休息1分钟），在此期间他们饮用了6%的CHO溶液（n = 8）、6克EAA混合物（n = 8）、CHO + EAA混合补充剂（n = 8）或安慰剂（PLA；n = 8）饮料。与CHO和CHO + EAA摄入同时进行的抗阻运动，导致葡萄糖和胰岛素浓度显著升高（P <.001），高于基线水平，而摄入EAA仅增加了运动后的胰岛素反应（P <.05）。在60分钟时进行时间匹配，PLA组的皮质醇峰值增加了105%（P <.001），而葡萄糖或胰岛素浓度无显著变化。相反，CHO组和CHO + EAA组的皮质醇水平分别下降了11%和7%。与这些激素反应模式一致的是，肌原纤维蛋白降解存在显著差异。在运动后48小时，摄入EAA和CHO处理可减少3 - MH排泄。此外，当两种处理联合使用时，这种反应具有协同增强作用，摄入CHO + EAA可使3 - MH排泄减少27%（P <.01）。相比之下，PLA组的3 - MH排泄增加了56%（P <.01）。这些数据表明，运动期间摄入CHO和EAA不仅能抑制运动诱导的皮质醇释放；抗阻运动对肌原纤维蛋白降解的刺激作用也可被减弱，当联合使用（CHO + EAA）时这种作用最为显著。通过“抗分解代谢作用”，这种改变的平衡可能更有利于肌原纤维蛋白的保存。
