Cescon Corrado, Sguazzi Elena, Merletti Roberto, Farina Dario
Laboratorio di Ingegneria del Sistema Neuromuscolare, Dipartimento di Elettronica, Politecnico di Torino, Torino, Italy.
J Electromyogr Kinesiol. 2006 Feb;16(1):17-24. doi: 10.1016/j.jelekin.2005.02.005. Epub 2005 Aug 19.
The aim of the study was to investigate amplitude and frequency content of single motor unit (MU) electromyographic (EMG) and mechanomyographic (MMG) responses. Multi-channel surface EMG and MMG signals were detected from the dominant biceps brachii muscle of 10 volunteers during isometric voluntary contractions at 20%, 50%, and 80% of the maximal voluntary contraction (MVC) force. Each contraction was performed three times in the experimental session which was repeated in three non-consecutive days. Single MU action potentials were identified from the surface EMG signals and their times of occurrence used to trigger the averaging of the MMG signal. At each contraction level, the MUs with action potentials of highest amplitude were identified. Single MU EMG and MMG amplitude and mean frequency were estimated with normalized standard error of the mean within subjects (due to repetition of the measure in different trials and experimental sessions) smaller than 15% and 7%, respectively, in all conditions. The amplitude of the action potentials of the detected MUs increased with increasing force (mean +/- SD, 244 +/- 116 microV at 20% MVC, and 1426 +/- 638 microV at 80% MVC; P < 0.001) while MU MMG amplitude increased from 20% to 50% MVC (40.5 +/- 20.9 and 150 +/- 88.4 mm/s(2), respectively; P<0.001) and did not change significantly between 50% and 80% MVC (129 +/ -82.7 mm/s(2) at 80% MVC). MU EMG mean frequency decreased with contraction level (20% MVC: 97.2 +/- 13.9 Hz; 80% MVC: 86.2 +/- 11.4 Hz; P < 0.001) while MU MMG mean frequency increased (20% MVC: 33.2 +/- 6.8 Hz; 80% MVC: 40.1 +/- 6.1 Hz; P < 0.001). EMG peak-to-peak amplitude and mean frequency of individual MUs were not correlated with the corresponding variables of MMG at any contraction level.
本研究的目的是调查单个运动单位（MU）肌电图（EMG）和肌机械图（MMG）反应的幅度和频率成分。在10名志愿者的优势肱二头肌进行等长自主收缩时，分别以最大自主收缩（MVC）力的20%、50%和80%检测多通道表面EMG和MMG信号。每次收缩在实验环节中进行3次，并在三个不连续的日子里重复。从表面EMG信号中识别出单个MU动作电位，并利用其发生时间触发MMG信号的平均化处理。在每个收缩水平，识别出具有最高幅度动作电位的运动单位。在所有条件下，单个MU的EMG和MMG幅度以及平均频率的估计值在受试者内部的平均归一化标准误差分别小于15%和7%（由于在不同试验和实验环节中重复测量）。检测到的运动单位动作电位的幅度随力量增加而增大（平均值±标准差，20%MVC时为244±116微伏，80%MVC时为1426±638微伏；P<0.001），而运动单位MMG幅度从20%MVC增加到50%MVC（分别为40.5±20.9和150±88.4毫米/秒²；P<0.001），在50%和80%MVC之间无显著变化（80%MVC时为129±82.7毫米/秒²）。运动单位EMG平均频率随收缩水平降低（20%MVC：97.2±13.9赫兹；80%MVC：86.2±11.4赫兹；P<0.001），而运动单位MMG平均频率增加（20%MVC：33.2±6.8赫兹；80%MVC：40.1±6.1赫兹；P<0.001）。在任何收缩水平，单个运动单位的EMG峰峰值幅度和平均频率与MMG的相应变量均无相关性。
