The purpose of the study was to examine the fatigue-related patterns of responses for electromyography (EMG), mechanomyography (MMG), and force during a sustained isometric muscle action anchored to RPE = 5. Ten men (22.9 ± 2.0 year) performed maximal voluntary isometric contractions (MVIC) prior to and following an isometric leg extension muscle action, which was sustained for a maximal time-limit of 5 min or until it could not be maintained at RPE = 5 (actual time-limit). EMG amplitude (AMP), EMG mean power–frequency (MPF), MMG AMP, MMG MPF, and force values were determined every 5% of the actual time-limit. Regression analyses were used to examine the neuromuscular parameters and force responses, and a t test was used to examine MVIC. The pretest MVIC (62.4 ± 14.3 kg) was significantly (p < 0.001; d = 1.07) greater than posttest (47.9 ± 12.8 kg). The percent decline in force during the sustained isometric muscle action was 47.5 ± 19.6%, and there was a significant, negative force versus time relationship (p < 0.001; R = − 0.980). There was a significant, negative EMG AMP versus time relationship (p < 0.001; R = -0.789), but no significant (p > 0.05) relationships for EMG MPF, MMG AMP, or MMG MPF versus time. The findings indicated that it was necessary to reduce force and EMG AMP to maintain RPE = 5. We hypothesize that the maintenance of RPE = 5 was initially accomplished by an anticipatory feedforward mechanism and then continuous integrations of afferent feedback, which resulted in reductions of EMG AMP and force, due to reductions in neural drive, to attenuate the impact of metabolic byproducts.

中文翻译：

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疲劳等距腿部伸展疲劳期间的自我调节力和神经肌肉反应锚定为一定程度的知觉运动。

这项研究的目的是检查与疲劳相关的肌电图（EMG），机械X线照相法（MMG）和在等距肌肉上固定于RPE = 5的力的响应方式。十名男性（22.9±2.0岁）等距腿部伸展肌肉动作之前和之后的自愿等距收缩（MVIC），该动作持续最大时间限制为5分钟，或者直到无法维持为RPE = 5（实际时间限制）为止。每实际时间限制的5％确定EMG振幅（AMP），EMG平均功率频率（MPF），MMG AMP，MMG MPF和力值。回归分析用于检查神经肌肉参数和力响应，t检验用于检查MVIC。预测试MVIC（62.4±14.3 kg）显着（p <0.001; d  = 1.07）大于后期测试（47.9±12.8 kg）。在持续的等距肌肉动作过程中，力量下降的百分比为47.5±19.6％，并且存在显着的负力与时间的关系（p  <0.001; R = − 0.980）。EMG AMP与时间之间存在显着负相关（p <0.001; R = -0.789），但EMG MPF，MMG AMP或MMG MPF与时间之间无显着（p> 0.05）关系。研究结果表明，有必要降低力量和EMG AMP来维持RPE =5。我们假设RPE = 5的维持最初是通过预期的前馈机制实现的，然后连续整合传入反馈，从而导致EMG减少由于神经驱动力的减少，AMP和力减弱了代谢副产物的影响。