Time and frequency domain responses of the mechanomyogram and electromyogram during isometric ramp contractions: A comparison of the short-time Fourier and continuous wavelet transforms
Time and frequency domain responses of the mechanomyogram and electromyogram during isometric ramp contractions: A comparison of the short-time Fourier and continuous wavelet transforms
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DOI：
10.1016/j.jelekin.2006.09.003
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发表时间：
2008-02-01
影响因子：
2.5
通讯作者：
Herda, Trent J.
中科院分区：
文献类型：
--
作者：
Ryan, Eric D.;Cramer, Joel T.;Herda, Trent J.
本研究的目的是检查股外侧肌（VL）和股直肌（RF）在等长斜坡收缩过程中的机械肌电（MMG）和肌电图（EMG）时域和频域响应，并比较由短时傅立叶变换（STFT）和连续小波变换（CWT）产生的MMG和EMG信号的时频特性。19名健康受试者（平均值+/- SD年龄= 24 +/- 4岁）在用右腿伸肌完成2-3，6-s等长斜坡收缩（从5%到100%MVC）之前和之后进行了两次等长最大自主收缩（MVC）。从VL和RF肌肉记录MMG和表面EMG信号。时域表示为均方根幅度值，并使用STFT和CWT生成时频表示。多项式回归分析表明MMG振幅、MMG频率和EMG频率呈三次增加，而EMG振幅呈二次增加。从5%到24- 28%MVC，MMG振幅保持稳定，而MMG频率增加。从24- 28%MVC到76- 78%MVC，MMG振幅迅速增加，而MMG频率稳定。从76-78%到100%MVC，MMG振幅稳定（VL）或降低（RF），而MMG频率增加。EMG振幅增加，而EMG频率在整个力谱中仅略有变化，没有明确的偏转点。总的来说，这些研究结果表明，MMG可能提供更多的独特的信息之间的相互作用的运动单位招聘和发射率，控制肌肉力量的生产过程中斜坡收缩比传统的表面肌电图。此外，虽然STFT频率模式比CWT更明显，但两种算法都产生了类似的时间-频率表示，用于跟踪MMG或EMG频率的变化。(C)2006爱思唯尔有限公司版权所有。
The purposes of this study were to examine the mechanomyographic (MMG) and electromyographic (EMG) time and frequency domain responses of the vastus lateralis (VL) and rectus femoris (RF) muscles during isometric ramp contractions and compare the time-frequency of the MMG and EMG signals generated by the short-time Fourier transform (STFT) and continuous wavelet transform (CWT). Nineteen healthy subjects (mean +/- SD age = 24 +/- 4 years) performed two isometric maximal voluntary contractions (MVCs) before and after completing 2-3, 6-s isometric ramp contractions from 5% to 100% MVC with the right leg extensors. MMG and surface EMG signals were recorded from the VL and RF muscles. Time domains were represented as root mean squared amplitude values, and time-frequency representations were generated using the STFT and CWT. Polynomial regression analyses indicated cubic increases in MMG amplitude, MMG frequency, and EMG frequency, whereas EMG amplitude increased quadratically. From 5% to 24-28% MVC, MMG amplitude remained stable while MMG frequency increased. From 24-28% to 76-78% MVC, MMG amplitude increased rapidly while MMG frequency plateaued. From 76-78% to 100% MVC, MMG amplitude plateaued (VL) or decreased (RF) while MMG frequency increased. EMG amplitude increased while EMG frequency changed only marginally across the force spectrum with no clear deflection points. Overall, these findings suggested that MMG may offer more unique information regarding the interactions between motor unit recruitment and firing rate that control muscle force production during ramp contractions than traditional surface EMG. In addition, although the STFT frequency patterns were more pronounced than the CWT, both algorithms produced similar time-frequency representations for tracking changes in MMG or EMG frequency. (C) 2006 Elsevier Ltd. All rights reserved.