Muza S R, Young A J, Sawka M N, Pandolf K B, Bogart J E
Aviat Space Environ Med. 1986 Dec;57(12 Pt 1):1150-3.
The purpose of this study was to describe the frequency content of the electromyogram (EMG) recorded during shivering and determine if the EMG power spectrum changed as a function of the shivering duration. Six semi-nude males were exposed to cold air (5 degrees C, 20% rh) for 80 min while quietly sitting. Rectal (Tre) and mean skin (Tsk) temperatures were recorded. Shivering of the masseter muscle was determined using bipolar surface electrodes. The EMG was amplified, recorded, and subsequently digitized at 2048 Hz. The power spectrum was calculated from eight serial 0.25s EMG samples by Fourier analysis from a frequency of 4 through 480 Hz. The eight power spectra were averaged and centroid frequency (fc) calculated. During the first 10 min of exposure, Tsk rapidly dropped from 32.6 +/- 1.6 to 26.2 +/- 1.3 degrees C, then slowly declined reaching 22.5 +/- 0.7 degrees C after 80 min. Tre rose from 37.1 +/- 0.1 to 37.4 +/- 0.1 degrees C, declining after 40 min to 37.2 +/- 0.1 degrees C. Shivering was observed within 5 min after entering the cold chamber. EMG activity after 10 min exhibited an fc of 177.2 +/- 6.2 Hz. When power was integrated over 60 Hz bandwidths, the predominant frequency band of the EMG power spectrum was 60-120 Hz. Although shivering intensity increased with time, the EMG power spectrum exhibited no significant changes. These results suggest that the EMG power spectrum during shivering did not exhibit changes characteristic of muscle fatigue or muscle cooling during the 80-min cold air exposure.
本研究的目的是描述寒颤期间记录的肌电图（EMG）的频率成分，并确定EMG功率谱是否随寒颤持续时间而变化。六名半裸男性安静坐着时暴露于冷空气（5摄氏度，相对湿度20%）中80分钟。记录直肠温度（Tre）和平均皮肤温度（Tsk）。使用双极表面电极确定咬肌的寒颤情况。EMG被放大、记录，随后以2048Hz进行数字化处理。通过对4至480Hz频率范围内的八个连续0.25秒EMG样本进行傅里叶分析来计算功率谱。将这八个功率谱进行平均并计算质心频率（fc）。在暴露的前10分钟内，Tsk迅速从32.6±1.6摄氏度降至26.2±1.3摄氏度，然后缓慢下降，80分钟后达到22.5±0.7摄氏度。Tre从37.1±0.1摄氏度升至37.4±0.1摄氏度，40分钟后降至37.2±0.1摄氏度。进入冷室后5分钟内观察到寒颤。10分钟后的EMG活动显示fc为177.2±6.2Hz。当功率在60Hz带宽上积分时，EMG功率谱的主要频段为60 - 120Hz。尽管寒颤强度随时间增加，但EMG功率谱未显示出显著变化。这些结果表明，在80分钟的冷空气暴露期间，寒颤期间的EMG功率谱未表现出肌肉疲劳或肌肉冷却的特征性变化。
