Department of Health Sciences, Program of Exercise Science, APEX Building, Room # 219, Lehman College, CUNY, 250 Bedford Park Blvd West, Bronx, NY, 10468, USA,
Sports Med. 2013 Dec;43(12):1279-88. doi: 10.1007/s40279-013-0088-z.
In humans, regimented resistance training has been shown to promote substantial increases in skeletal muscle mass. With respect to traditional resistance training methods, the prevailing opinion is that an intensity of greater than ~60 % of 1 repetition maximum (RM) is necessary to elicit significant increases in muscular size. It has been surmised that this is the minimum threshold required to activate the complete spectrum of fiber types, particularly those associated with the largest motor units. There is emerging evidence, however, that low-intensity resistance training performed with blood flow restriction (BFR) can promote marked increases in muscle hypertrophy, in many cases equal to that of traditional high-intensity exercise. The anabolic effects of such occlusion-based training have been attributed to increased levels of metabolic stress that mediate hypertrophy at least in part by enhancing recruitment of high-threshold motor units. Recently, several researchers have put forth the theory that low-intensity exercise (≤50 % 1RM) performed without BFR can promote increases in muscle size equal, or perhaps even superior, to that at higher intensities, provided training is carried out to volitional muscular failure. Proponents of the theory postulate that fatiguing contractions at light loads is simply a milder form of BFR and thus ultimately results in maximal muscle fiber recruitment. Current research indicates that low-load exercise can indeed promote increases in muscle growth in untrained subjects, and that these gains may be functionally, metabolically, and/or aesthetically meaningful. However, whether hypertrophic adaptations can equal that achieved with higher intensity resistance exercise (≤60 % 1RM) remains to be determined. Furthermore, it is not clear as to what, if any, hypertrophic effects are seen with low-intensity exercise in well-trained subjects as experimental studies on the topic in this population are lacking. Practical implications of these findings are discussed.
在人类中，有规律的抗阻训练已被证明可以显著增加骨骼肌质量。关于传统的抗阻训练方法，普遍认为需要超过约 60%的 1 次重复最大值（1RM）的强度才能引起肌肉大小的显著增加。据推测，这是激活所有纤维类型的最小阈值，特别是那些与最大运动单位相关的纤维类型。然而，有新的证据表明，低强度抗阻训练与血流限制（BFR）结合使用可以显著促进肌肉肥大，在许多情况下，与传统的高强度运动相当。这种基于闭塞的训练的合成代谢效应归因于代谢应激水平的增加，这种应激至少部分通过增强高阈值运动单位的募集来介导肥大。最近，一些研究人员提出了这样一种理论，即在没有 BFR 的情况下进行的低强度运动（≤50%1RM）可以促进肌肉大小的增加，与更高强度的运动一样，或者甚至更好，只要训练进行到自愿性肌肉疲劳。该理论的支持者假设，轻负荷下的疲劳收缩只是 BFR 的一种更温和的形式，因此最终会导致最大的肌肉纤维募集。目前的研究表明，低负荷运动确实可以促进未经训练的受试者的肌肉生长增加，这些收益在功能、代谢和/或美学上可能是有意义的。然而，低强度运动是否能与更高强度的抗阻运动（≤60%1RM）所达到的肥大适应相媲美，还有待确定。此外，在这个人群中，关于这个主题的实验研究缺乏，因此尚不清楚在训练有素的受试者中，低强度运动是否会产生任何肥大效应。讨论了这些发现的实际意义。
