Evans W J
Nutrition, Metabolism, and Exercise Laboratory, Donald W. Reynolds Center on Aging, University of Arkansas for Medical Sciences, Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA.
Can J Appl Physiol. 2001;26 Suppl:S141-52. doi: 10.1139/h2001-049.
Strength conditioning will result in an increase in muscle size and this increase in size is largely the result of increased contractile proteins. The mechanisms by which the mechanical events stimulate an increase in RNA synthesis and subsequent protein synthesis are not well understood. Lifting weight requires that a muscle shorten as it produces force (concentric contraction). Lowering the weight forces the muscle to lengthen as it produces force (eccentric contraction). Eccentric contractions produce ultrastructural damage that may stimulate increased muscle protein turnover and a cascade of metabolic events which is similar to an acute phase response and includes complement activation, mobilization of neutrophils, increased circulating and skeletal muscle interleukin-1 and macrophage accumulation. While endurance exercise increases the oxidation of essential amino acids and increases the requirement for dietary protein, resistance exercise results in a decrease in nitrogen excretion, lowering dietary protein needs. Research has indicated that increased dietary protein intake (up to 1.6 g protein x kg(-1) x d(-1)) may enhance the hypertrophic response to resistance exercise. It has also been demonstrated that in very old men and women the use of a protein-calorie supplement was associated with greater strength and muscle mass gains than did the use of placebo.
力量训练会导致肌肉尺寸增加，而这种尺寸的增加很大程度上是收缩蛋白增加的结果。机械事件刺激RNA合成增加以及随后的蛋白质合成增加的机制尚未完全了解。举重要求肌肉在产生力量时缩短（向心收缩）。放下重物时，肌肉在产生力量时被迫拉长（离心收缩）。离心收缩会产生超微结构损伤，这可能会刺激肌肉蛋白质更新增加以及一系列代谢事件，这类似于急性期反应，包括补体激活、中性粒细胞动员、循环和骨骼肌白细胞介素-1增加以及巨噬细胞聚集。虽然耐力运动增加必需氨基酸的氧化并增加对膳食蛋白质的需求，但抗阻运动导致氮排泄减少，从而降低膳食蛋白质需求。研究表明，增加膳食蛋白质摄入量（高达1.6克蛋白质×千克⁻¹×天⁻¹）可能会增强对抗阻运动的肥大反应。还证明，在非常年长的男性和女性中，使用蛋白质热量补充剂比使用安慰剂能带来更大的力量和肌肉量增加。
