Häkkinen K
Department of Biology of Physical Activity, University Jyväskylä, Finland.
Electromyogr Clin Neurophysiol. 1995 Nov;35(7):403-13.
To examine neuromuscular fatigue and recovery 23 women, divided into three different age groups, i.e. young women (YW); 30 years (25.0 +/- 1.4; n = 8), middle-aged women (MW); 50 years (48.0 +/- 3.7; n = 7) and elderly women (EW); 70 years (68.9 +/- 3.2; n = 8) performed a strenuous heavy resistance exercise protocol. The subjects performed a bilateral leg press exercise on the machine (David 210) for 5 sets by performing 10 repetitions in each set with the maximal load possible (10 RM). A recovery time of 3 minutes was allowed between the sets. Maximal voluntary neutral activation (integrated EMG), maximal bilateral isometric force, force-time and relaxation time curves of the leg extensor muscles were measured before, between the sets, and immediately after the loading as well as resting for 1 hour, 2 hours, 1 day and 2 days. The loading led to gradual decreases in maximal force in YW by 18.8 +/- 7.1% (p < 0.001), in MW by 30.9 +/- 14.8% (p < 0.01) and in EW by 13.7 +/- 11.9% (p < 0.01) so that the relative decrease in EW was smaller (p < 0.05) than the averaged decreases in YW and MW. Significant (p < 0.05) decreases also took place in the maximal IEMGs of the exercised muscles in all groups. The force-time curve shifted also significantly both in YW (p < 0.001) and in MW (p < 0.001), while only a slight change occurred in EW. Acute recovery in maximal force was significant (p < 0.05) during the first hour of rest in YW and in MW but the force values in all groups were still after two hours of rest significantly (p < 0.05) lower than the preloading values. After two days of rest the force values were 93.7 +/- 11.5% (ns), 90.6 +/- 19.2% (p < 0.05) and 94.6 +/- 17.1% (ns) from their initial force values in YW, MW and EW, respectively. The present results suggest that strenuous heavy resistance loading both in young and middle-aged as well as in elderly women may result in considerable acute fatigue in the neuromuscular system leading not only to the decreased force production capacity of the muscles but also some decrease in the voluntary neural activation of the exercised muscles. Because the degree of acute neuromuscular fatigue and the time needed for recovery may differ considerably, there is a need to optimize the contents and the frequency of different training sessions in order to create proper strength training and for rehabilitation programs to match with the individual requirements of young, middle-aged and elderly women.
为研究神经肌肉疲劳与恢复情况，23名女性被分为三个不同年龄组，即年轻女性（YW），年龄30岁（25.0±1.4岁；n = 8）；中年女性（MW），年龄50岁（48.0±3.7岁；n = 7）；老年女性（EW），年龄70岁（68.9±3.2岁；n = 8），她们进行了一项高强度重阻力运动方案。受试者在器械（David 210）上进行双侧腿举运动，共5组，每组进行10次重复，使用尽可能大的负荷（10RM）。每组之间允许3分钟的恢复时间。在负荷前、组间、负荷后即刻以及休息1小时、2小时、1天和2天后，测量腿部伸肌的最大自主神经激活（积分肌电图）、最大双侧等长力、力-时间和放松时间曲线。负荷导致YW组最大力量逐渐下降18.8±7.1%（p < 0.001），MW组下降30.9±14.8%（p < 0.01），EW组下降13.7±11.9%（p < 0.01），因此EW组的相对下降幅度小于YW组和MW组的平均下降幅度（p < 0.05）。所有组中，运动肌肉的最大积分肌电图也出现了显著（p < 0.05）下降。YW组（p < 0.001）和MW组（p < 0.001）的力-时间曲线也发生了显著变化，而EW组仅出现轻微变化。休息的第1小时，YW组和MW组的最大力量急性恢复显著（p < 0.05），但休息2小时后，所有组的力量值仍显著（p < 0.05）低于负荷前的值。休息两天后，YW组、MW组和EW组的力量值分别为初始力量值的93.7±- 11.5%（无显著性差异）、90.6±19.2%（p < 0.05）和94.6±17.1%（无显著性差异）。目前的结果表明，年轻、中年以及老年女性进行高强度重阻力负荷运动可能会导致神经肌肉系统出现相当程度的急性疲劳，这不仅会导致肌肉力量产生能力下降，还会使运动肌肉的自主神经激活有所降低。由于急性神经肌肉疲劳的程度和恢复所需时间可能有很大差异，因此有必要优化不同训练课程的内容和频率，以便制定合适的力量训练和康复计划，以满足年轻、中年和老年女性的个体需求。
