Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
Eur J Sport Sci. 2024 Sep;24(9):1328-1340. doi: 10.1002/ejsc.12181. Epub 2024 Aug 8.
The measurement of skeletal muscle fatigue in response to cycling exercise is commonly done in isometric conditions, potentially limiting its ecological validity, and creating challenges in monitoring the time course of muscle fatigue across an exercise bout. This study aimed to determine if muscle fatigue could be reliably assessed by measuring quadriceps twitch force evoked while pedaling, using instrumented pedals. Nine participants completed three laboratory visits: a step incremental test to determine power output at lactate threshold, and on separate occasions, two constant-intensity bouts at a power output 10% above lactate threshold. Femoral nerve electrical stimulation was applied to elicit quadriceps twitch force both while pedaling (dynamic) and at rest (isometric). The test-retest reliability of the dynamic twitch forces and the agreement between the dynamic and isometric twitch forces were evaluated. Dynamic twitch force was found to have excellent reliability in an unfatigued state (intraclass correlation coefficient (ICC) = 0.920 and mean coefficient of variation (CV) = 7.5%), and maintained good reliability at task failure (ICC = 0.846 and mean CV = 11.5%). When comparing dynamic to isometric twitch forces across the task, there was a greater relative decline in the dynamic condition (P = 0.001). However, when data were normalized to the 5 min timepoint when potentiation between conditions was presumed to be more similar, this difference disappeared (P = 0.207). The reliability of this method was shown to be commensurate with the gold standard method utilizing seated isometric dynamometers and offers a new avenue to monitor the kinetics of muscle fatigue during cycling in real time.
在进行自行车运动时，通常在等长条件下测量骨骼肌疲劳，这可能限制了其生态有效性，并在监测整个运动过程中肌肉疲劳的时间进程方面带来挑战。本研究旨在确定是否可以通过测量蹬踏时诱发的股四头肌颤搐力来可靠地评估肌肉疲劳，使用带仪器的脚踏板。9 名参与者完成了三次实验室访问：一次递增测试以确定乳酸阈下的功率输出，以及在单独的场合，两次以高于乳酸阈 10%的功率输出进行的恒定强度运动。股神经电刺激用于在蹬踏时（动态）和休息时（等长）诱发股四头肌颤搐力。评估了动态颤搐力的测试-重测可靠性和动态与等长颤搐力之间的一致性。在未疲劳状态下，动态颤搐力具有极好的可靠性（组内相关系数 (ICC) = 0.920，平均变异系数 (CV) = 7.5%），在任务失败时仍保持良好的可靠性（ICC = 0.846，平均 CV = 11.5%）。当将动态与等长颤搐力在整个任务中进行比较时，动态条件下的相对下降更大（P = 0.001）。然而，当将数据归一化到条件之间的增强作用被认为更相似的 5 分钟时间点时，这种差异消失（P = 0.207）。该方法的可靠性与使用坐姿等长测力计的金标准方法相当，并为实时监测自行车运动中肌肉疲劳的动力学提供了新途径。
