Health and Physical Education Department, Mount Royal University, Mount Royal Gate SW, Calgary, AB T3E 6K6, Canada.
Center of Sports, Federal University of Santa Catarina, UFSC Campus Trindade, Av. César Seara, Florianópolis, SC 88040-900, Brazil.
J Electromyogr Kinesiol. 2020 Jun;52:102425. doi: 10.1016/j.jelekin.2020.102425. Epub 2020 May 4.
This study aimed to assess the validity of the first (EMGth1) and second (EMGth2) breakpoints in the EMG signal during skating.
Ten well-trained long track speed skaters performed a maximal incremental skating test on a slide board. EMG signals from six lower limb muscles were recorded during the last 15 s of each stage and converted to Root Mean Square for determination EMGth1 and EMGth2 using mathematical (2 and 3 linear regressions) and visual methods.
EMGth1 had a low detection rate (<50%) while EMGth2 could be identified visually in > 80% of cases, in 85% of cases using 2-lines and 63% using 3-lines regression. Quads (VL + VM) and Gluts (GM + GMd) had the highest EMGth2 detection rate for all methods (>70%). EMGth2 from Quads and Gluts detected by the 2-lines and 3-lines regression were not different than the second ventilatory threshold (VT2) (p > 0.05), while the visual method overestimated VT2 (p < 0.01). EMGth2 detected from Quads by the 2-lines regression method presented better correlation with VT2 stage (r = 0.91), lowest bias, and limit of agreement. We conclude that EMG is a valid non-invasive method to detect VT2 during skating when using a mathematical method to determine EMGth2.
本研究旨在评估在滑冰过程中肌电图信号的第一个（EMGth1）和第二个（EMGth2）断点的有效性。
10 名训练有素的长道速滑运动员在滑垫上进行最大增量滑冰测试。在每个阶段的最后 15 秒记录了来自六个下肢肌肉的肌电图信号，并将其转换为均方根，以使用数学（2 线和 3 线回归）和视觉方法确定 EMGth1 和 EMGth2。
EMGth1 的检测率较低（<50%），而 EMGth2 可以通过视觉方法在>80%的情况下识别，使用 2 线和 3 线回归分别在 85%和 63%的情况下识别。对于所有方法，四头肌（VL+VM）和臀肌（GM+GMd）的 EMGth2 检测率最高（>70%）。使用 2 线和 3 线回归法从四头肌和臀肌检测到的 EMGth2 与第二个通气阈值（VT2）没有差异（p>0.05），而视觉方法高估了 VT2（p<0.01）。使用 2 线回归法从四头肌检测到的 EMGth2 与 VT2 阶段的相关性更好（r=0.91），偏差和一致性界限最低。我们得出结论，当使用数学方法确定 EMGth2 时，肌电图是一种有效的非侵入性方法，可以在滑冰时检测 VT2。
