Croce R V, Miller J P
Motor Control and Biomechanics Laboratory, Department of Kinesiology, University of New Hampshire, USA.
Electromyogr Clin Neurophysiol. 2003 Dec;43(8):451-8.
The effect of velocity and movement pattern (reciprocal vs. non-reciprocal) on the reciprocal co-activation of the hamstrings was investigated through analysis of the root mean square (RMS) and the median frequency (MDF) of surface electromyography (SEMG). Fourteen subjects performed six continuous repetitions of a reciprocal isokinetic movement pattern (maximal extension followed by maximal flexion), and six continuous repetitions of a non-reciprocal movement pattern (maximal extension only) at 100 degrees, 200 degrees, 300 degrees s-1, and 400 degrees s-1. Data were analyzed using separate 2 x 4 (movement pattern x angular velocity) repeated measures analysis of variance (ANOVA). No significant differences (p > 0.05) were noted between reciprocal and non-reciprocal movement patterns for RMS. However, results did reveal a velocity effect for RMS (F = 5.0, p < 0.01), with significant differences observed between 100 degrees s-1 and 400 degrees s-1 (F = 9.4, p < 0.01), 200 degrees s-1 and 400 degrees s-1 (F = 9.5, p < 0.01), and 300 degrees s-1 and 400 degrees s-1 (F = 11.0, p < 0.001), with RMS values at 400 degrees s-1 being the highest. There was also a velocity effect for MDF (F = 8.03, p < 0.001), with significant differences observed between 100 degrees s-1 and 300 degrees s-1 (F = 4.2, p < 0.05), 100 degrees s-1 and 400 degrees s-1 (F = 20.2, p < 0.0001), 200 degrees s-1 and 400 degrees s-1 (F = 15.221, p < 0.001), and 300 degrees s-1 and 400 degrees s-1 (F = 5.9, p < 0.01). In all cases the highest MDF values were exhibited at the lower velocities. Lastly, there was an interaction effect when comparing movement patterns at 400 degrees s-1, with MDF values being significantly higher during the non-reciprocal movement pattern than during the reciprocal movement pattern (F = 10.9, p < 0.01). Results indicated that during isokinetic movements, RMS and MDF activity of the hamstrings are altered as velocity changes. More specifically, as velocity increases overall hamstrings' co-activation increases and there is a shift in the power spectrum toward the recruitment of slower-twitch muscle fibers. Results also indicate that movement pattern (reciprocal vs. non reciprocal) does not effect appreciably SEMG activity of hamstrings' co-contraction.
通过分析表面肌电图（SEMG）的均方根（RMS）和中位频率（MDF），研究了速度和运动模式（往复式与非往复式）对腘绳肌往复协同激活的影响。14名受试者以100度/秒、200度/秒、300度/秒和400度/秒的速度进行了6次连续重复的往复等速运动模式（最大伸展后接着最大屈曲），以及6次连续重复的非往复运动模式（仅最大伸展）。使用单独的2×4（运动模式×角速度）重复测量方差分析（ANOVA）对数据进行分析。对于RMS，往复式和非往复式运动模式之间未观察到显著差异（p>0.05）。然而，结果确实显示出RMS的速度效应（F=5.0，p<0.01），在100度/秒和400度/秒之间（F=9.4，p<0.01）、200度/秒和400度/秒之间（F=9.5，p<0.01）以及300度/秒和400度/秒之间（F=11.0，p<0.001）观察到显著差异，400度/秒时的RMS值最高。MDF也存在速度效应（F=8.03，p<0.001），在100度/秒和300度/秒之间（F=4.2，p<0.05）、100度/秒和400度/秒之间（F=20.2，p<0.0001）、200度/秒和400度/秒之间（F=15.221，p<0.001）以及300度/秒和400度/秒之间（F=5.9，p<0.01）观察到显著差异。在所有情况下，较低速度时MDF值最高。最后，在比较400度/秒时的运动模式时存在交互效应，非往复运动模式期间的MDF值显著高于往复运动模式期间（F=10.9，p<0.01）。结果表明，在等速运动期间，腘绳肌的RMS和MDF活动随速度变化而改变。更具体地说，随着速度增加，腘绳肌的整体协同激活增加，并且功率谱向募集慢肌纤维方向转移。结果还表明，运动模式（往复式与非往复式）对腘绳肌协同收缩的SEMG活动没有明显影响。
