Bilodeau M, Goulet C, Nadeau S, Arsenault A B, Gravel D
Ecole de réadaptation, Faculté de médecine, Université de Montréal, QC, Canada.
Eur J Appl Physiol Occup Physiol. 1994;68(5):395-401. doi: 10.1007/BF00843735.
The purpose of this study was to compare the behaviour of electromyographic (EMG) power spectrum statistics, mean power frequency (MPF) and median frequency (MF), across increasing force levels of the soleus (SO), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscles. Surface EMG signals of these three muscles were recorded in 12 men and 10 women during both (1) ramp (single ongoing contractions with the force increasing linearly from 0 to 100% of the maximum voluntary contraction (MVC); and (2) step (steady force levels: 10, 20, 30, 40, 60 and 80% MVC) static (isometric) plantar flexions. Power spectral analysis of these signals was performed on single 256-ms windows at all of the above-mentioned force levels, for both types of contraction. The MF and MPF were calculated from each of the obtained spectra. A less pronounced increase in the MF or MPF was expected for the SO because of its higher type I fibre content. The main results are as follows: (1) similar behaviours were found in the value of MPF and MF across increasing force for the SO and GL muscles, while the GM gave rise to a different behaviour; (2) no difference was found between ramp and step contractions in the behaviour of either MF or MPF across force levels; and (3) different behaviours were observed between the MF and MPF across increasing force levels, for both ramp and step contractions. Our initial expectations were thus not confirmed. It is concluded that the present results support the hypothesis that the EMG power spectrum may be more sensitive to the diameter of the fibres than to the fibre type proportion of the triceps surae muscles. Furthermore, the sensitivity of the power spectrum statistics of a given muscle to the low-pass filter effect of its skin layer was also emphasized.
本研究的目的是比较比目鱼肌（SO）、内侧腓肠肌（GM）和外侧腓肠肌（GL）在不同力水平下肌电图（EMG）功率谱统计数据、平均功率频率（MPF）和中位数频率（MF）的表现。在12名男性和10名女性进行以下两种运动时，记录这三块肌肉的表面肌电信号：（1）斜坡运动（单次持续收缩，力从0线性增加到最大自主收缩（MVC）的100%）；（2）阶梯运动（稳定力水平：10%、20%、30%、40%、60%和80%MVC）静态（等长）跖屈。对上述所有力水平下两种收缩类型的信号，在单个256毫秒窗口上进行功率谱分析。从每个获得的频谱中计算MF和MPF。由于比目鱼肌I型纤维含量较高，预计其MF或MPF的增加不太明显。主要结果如下：（1）比目鱼肌和外侧腓肠肌在力增加时MPF和MF值的表现相似，而内侧腓肠肌表现不同；（2）在力水平上，MF或MPF在斜坡运动和阶梯运动中的表现没有差异；（3）在斜坡运动和阶梯运动中，随着力水平增加，MF和MPF之间观察到不同的表现。因此，我们最初的预期未得到证实。得出的结论是，目前的结果支持以下假设：EMG功率谱对比目鱼肌纤维直径可能比对其纤维类型比例更敏感。此外，还强调了给定肌肉的功率谱统计对其皮肤层低通滤波效应的敏感性。
