Cognition, Neuroplasticity, and Sarcopenia Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, USA; School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, FL, USA.
School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, FL, USA.
Brain Res. 2024 Nov 1;1842:149111. doi: 10.1016/j.brainres.2024.149111. Epub 2024 Jul 3.
The determination of active motor threshold (AMT) is a critical step in transcranial magnetic stimulation (TMS) research. As AMT is frequently determined using an absolute electromyographic (EMG) threshold (e.g., 200 µV peak-to-peak amplitude), wide variation in EMG recordings across participants has given reason to consider relative thresholds (e.g., = 2 × background sEMG) for AMT determination. However, these approaches have not been systemically compared. Our purpose was to compare AMT estimations derived from absolute and relative criteria commonly used in the quadriceps, and assess the test-retest reliability of each approach. We used a repeated measures design to assess AMT estimations in the vastus lateralis (VL) from eighteen young adults (9 males and 9 females; mean ± SD age = 23 ± 2 years) across two laboratory visits. AMT was determined for each criterion, at each lab visit. A paired samples t-test was used to compare mean differences in AMT estimations during the second laboratory visit. Paired samples t-tests and intraclass correlation coefficients (ICC) were calculated to assess test-retest reliability of each criterion. Differences between the criteria were small and not statistically significant (p = 0.309). The absolute criterion demonstrated moderate to excellent reliability (ICC = 0.866 [0.648-0.950]), but higher AMTs were observed in the second visit (p = 0.043). The relative criteria demonstrated good-to-excellent test-retest reliability (ICC = 0.894 [0.746-0.959]) and AMTs were not different between visits (p = 0.420). TMS researchers aiming to track corticospinal characteristics across visits should consider implementing relative criterion approaches during their AMT determination protocol.
主动运动阈值（AMT）的确定是经颅磁刺激（TMS）研究中的一个关键步骤。由于 AMT 通常使用绝对肌电图（EMG）阈值（例如，200µV 峰峰值幅度）来确定，因此参与者的 EMG 记录存在广泛差异，这使得人们有理由考虑相对阈值（例如，=2×背景 sEMG）来确定 AMT。然而，这些方法尚未系统地进行比较。我们的目的是比较在股四头肌中常用的绝对和相对标准下得出的 AMT 估计值，并评估每种方法的测试-重测可靠性。我们使用重复测量设计在两个实验室访问中评估了 18 名年轻成年人（9 名男性和 9 名女性；平均年龄 ± 标准差=23±2 岁）的外侧股直肌（VL）的 AMT 估计值。在每个实验室访问中，根据每个标准确定 AMT。使用配对样本 t 检验比较第二次实验室访问期间 AMT 估计值的平均差异。计算配对样本 t 检验和组内相关系数（ICC）以评估每个标准的测试-重测可靠性。标准之间的差异较小且无统计学意义（p=0.309）。绝对标准表现出中等到极好的可靠性（ICC=0.866 [0.648-0.950]），但在第二次访问中观察到更高的 AMT（p=0.043）。相对标准表现出良好到极好的测试-重测可靠性（ICC=0.894 [0.746-0.959]），并且两次访问之间的 AMT 没有差异（p=0.420）。希望在访问期间跟踪皮质脊髓特征的 TMS 研究人员应考虑在其 AMT 确定方案中实施相对标准方法。
