Lau Wing Yin, Blazevich Anthony J, Newton Michael J, Wu Sam Shi Xuan, Nosaka Kazunori
School of Exercise and Health Sciences, Center for Exercise and Sports Science Research Edith Cowan University, Joondalup, Western Australia, Australia; and.
School of Psychology and Exercise Science, Murdoch University, Murdoch, Western Australia, Australia.
Am J Physiol Regul Integr Comp Physiol. 2015 May 15;308(10):R879-86. doi: 10.1152/ajpregu.00338.2014. Epub 2015 Mar 25.
This study investigated biceps brachii distal myotendinous junction (MTJ) displacement during maximal eccentric elbow flexor contractions to test the hypothesis that muscle length change would be smaller (less MTJ displacement) during the second than the first exercise bout. Ten untrained men performed two eccentric exercise bouts (ECC1 and ECC2) with the same arm consisting of 10 sets of six maximal isokinetic (60°/s) eccentric elbow flexor contractions separated by 4 wk. Biceps brachii distal MTJ displacement was assessed using B-mode ultrasonography, and changes in the displacement (muscle length change) from the start to the end of each contraction during each set and over 10 sets were compared between bouts by two-way repeated-measures ANOVA. Several indirect muscle damage markers were also measured and compared between bouts by two-way repeated-measures ANOVA. The magnitude of MTJ displacement (average of six contractions) increased from set 1 (8.2 ± 4.7 mm) to set 10 (16.4 ± 4.7 mm) during ECC1 (P < 0.05), but no significant changes over sets were evident during ECC2 (set 1: 8.5 ± 4.0 mm; set 10: 9.3 ± 3.1 mm). Changes in maximal voluntary isometric contraction strength, range of motion, muscle thickness, ultrasound echo intensity, serum creatine kinase activity, and muscle soreness (visual analog scale) were smaller (P < 0.05) following ECC2 than ECC1, showing less damage in the repeated bout. These results indicate that the magnitude of muscle lengthening was less during the second than the first eccentric exercise bout, which appears to be a mechanism underpinning the repeated-bout effect.
本研究调查了在最大离心性屈肘收缩过程中肱二头肌远端肌腱结合部（MTJ）的位移情况，以验证以下假设：与第一次运动 bout 相比，第二次运动 bout 期间肌肉长度变化会更小（MTJ 位移更小）。10 名未经训练的男性用同一只手臂进行了两次离心运动 bout（ECC1 和 ECC2），每次 bout 包含 10 组，每组进行 6 次最大等速（60°/s）离心性屈肘收缩，两次 bout 间隔 4 周。使用 B 型超声评估肱二头肌远端 MTJ 位移，并通过双向重复测量方差分析比较两次 bout 期间每组及 10 组收缩过程中从开始到结束的位移变化（肌肉长度变化）。还测量了几种间接肌肉损伤标志物，并通过双向重复测量方差分析比较两次 bout 之间的差异。在 ECC1 期间，MTJ 位移幅度（6 次收缩的平均值）从第 1 组（8.2±4.7mm）增加到第 10 组（16.4±4.7mm）（P<0.05），但在 ECC2 期间，各组间无明显变化（第 1 组：8.5±4.0mm；第 10 组：9.3±3.1mm）。与 ECC1 相比，ECC2 后最大自主等长收缩力量、运动范围、肌肉厚度、超声回声强度、血清肌酸激酶活性和肌肉酸痛（视觉模拟评分）的变化更小（P<0.05），表明重复 bout 时损伤更小。这些结果表明，第二次离心运动 bout 期间肌肉拉长的幅度小于第一次，这似乎是重复 bout 效应的一种潜在机制。
