Rennie M J, Tipton K D
Department of Anatomy & Physiology, University of Dundee, Dundee DD1 4HN, Scotland.
Annu Rev Nutr. 2000;20:457-83. doi: 10.1146/annurev.nutr.20.1.457.
Sustained dynamic exercise stimulates amino acid oxidation, chiefly of the branched-chain amino acids, and ammonia production in proportion to exercise intensity; if the exercise is intense enough, there is a net loss of muscle protein (as a result of decreased protein synthesis, increased breakdown, or both); some of the amino acids are oxidized as fuel, whereas the rest provide substrates for gluconeogenesis and possibly for acid-based regulation. Protein balance is restored after exercise, but no hypertrophy occurs with habitual dynamic exercise. Resistance exercise causes little change in amino acid oxidation but probably depresses protein synthesis and elevates breakdown acutely. After exercise, protein synthesis rebounds for </=48 h, but breakdown remains elevated, and net positive balance is achieved only if amino acid availability is increased. There is no evidence that habitual exercise increases protein requirements; indeed protein metabolism may become more efficient as a result of training.
持续的动态运动刺激氨基酸氧化，主要是支链氨基酸的氧化，并按运动强度成比例产生氨；如果运动强度足够大，会出现肌肉蛋白净损失（由于蛋白质合成减少、分解增加或两者兼有）；一些氨基酸被氧化为燃料，其余的则为糖异生提供底物，可能还参与酸碱调节。运动后蛋白质平衡得以恢复，但习惯性动态运动不会导致肌肉肥大。抗阻运动对氨基酸氧化影响不大，但可能会急性抑制蛋白质合成并提高分解。运动后，蛋白质合成在≤48小时内反弹，但分解仍处于较高水平，只有增加氨基酸供应才能实现净正平衡。没有证据表明习惯性运动增加蛋白质需求；事实上，训练可能会使蛋白质代谢更高效。
