MacLennan Rob J, Mota Jacob A, Thompson Brennan J, Stock Matt S
School of Kinesiology and Physical Therapy, University of Central Florida, Orlando, Florida.
Department of Exercise and Sport Science, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina.
J Strength Cond Res. 2022 May 1;36(5):1318-1326. doi: 10.1519/JSC.0000000000003643. Epub 2021 Mar 25.
MacLennan, RJ, Mota, JA, Thompson, BJ, and Stock, MS. Effects of strength and conditioning on maximal isometric strength, motor unit behavior, and concentric isokinetic peak torque in middle-school boys. J Strength Cond Res 36(5): 1318-1326, 2022-It has long been theorized that improvements in muscle strength in young athletes are mediated by motor unit adaptations. The ability to decompose surface electromyographic signals obtained during isometric contractions now allow for such research questions to be answered. We examined changes in isometric and concentric isokinetic strength, as well as vastus lateralis motor unit behavior, after 16 weeks of strength training and conditioning in middle-school aged boys. Nine boys (mean ± SD age = 12 ± 1 years) participated in training. Five boys (age = 13 ± 1 years) served as control subjects. The training subjects performed 90 minutes of high-intensity, multi-joint exercise twice per week. Assessments of unilateral maximal voluntary isometric contraction (MVIC) force of the knee extensors, concentric peak torque at velocities of 60, 180, and 300°·s-1, and vastus lateralis motor unit data during 50 and 80% MVIC tests were performed. Strength training and conditioning did not improve MVIC force. Greater training-induced strength increases were observed at faster isokinetic velocities, with a large effect size at 300°·s-1 (d = 0.813). The slopes and y-intercepts of the mean firing rate vs. recruitment threshold relationship and the action potential amplitude vs. recruitment threshold relationship were unaffected by training. Sixteen weeks of middle-school strength and conditioning did not enhance maximal isometric strength or vastus lateralis motor unit control, but improvements were observed during rapid isokinetic muscle actions. Given the lack of training (multi-joint) vs. testing (single-joint) specificity, we propose that motor unit adaptations in youth are task specific.
麦克伦南，RJ；莫塔，JA；汤普森，BJ；斯托克，MS。力量训练与体能训练对初中男生最大等长肌力、运动单位行为及等速向心峰值扭矩的影响。《力量与体能训练研究杂志》36(5): 1318 - 1326，2022年。长期以来，理论上认为年轻运动员肌肉力量的提高是由运动单位适应性介导的。现在，对等长收缩期间获得的表面肌电信号进行分解的能力使得此类研究问题能够得到解答。我们研究了初中男生在进行16周的力量训练与体能训练后等长和等速向心肌力的变化，以及股外侧肌运动单位行为的变化。九名男生（平均±标准差年龄 = 12 ± 1岁）参与了训练。五名男生（年龄 = 13 ± 1岁）作为对照受试者。训练受试者每周进行两次90分钟的高强度多关节运动。对膝伸肌的单侧最大自主等长收缩（MVIC）力量、60、180和300°·s-1速度下的向心峰值扭矩以及50%和80% MVIC测试期间的股外侧肌运动单位数据进行了评估。力量训练与体能训练并未提高MVIC力量。在更快的等速速度下观察到更大的训练诱导力量增加，在300°·s-1时效应量较大（d = 0.813）。平均放电频率与募集阈值关系以及动作电位幅度与募集阈值关系的斜率和y轴截距不受训练影响。16周的初中力量训练与体能训练并未增强最大等长肌力或股外侧肌运动单位控制，但在快速等速肌肉动作期间观察到了改善。鉴于训练（多关节）与测试（单关节）缺乏特异性，我们提出青少年的运动单位适应性是任务特异性 的。
