Allison G T
The Centre for Musculoskeletal Studies, School of Surgery and Pathology, The University of Western Australia, Level 2 Medical Research Foundation Building, Rear 50 Murray Street, Perth 6000, Australia.
J Electromyogr Kinesiol. 2003 Jun;13(3):209-16. doi: 10.1016/s1050-6411(03)00019-1.
The timing of trunk muscle activation has become an important element in the understanding of human movement in normal and chronic low back pain populations. The detection of anticipatory postural adjustment via trunk muscle onsets from electromyographic (EMG) signals can be problematic due to baseline noise or electro-cardiac (ECG) artefact. Shewhart protocols or whole signal analyses may show different degrees of sensitivity under different conditions. Muscle activity onsets were determined from surface EMG of seven muscles for five trials before and after fatigue were examined in four subjects (n=280). The objective of this study was to examine two detection methods (Shewhart and integrated protocol (IP)) in determining the onsets of trunk muscles. The variability of the baseline amplitude and the impact of added Gaussian noise on the detected onsets were used to test for robustness. The results of this study demonstrate that before and after fatigue there is a large degree of baseline variance in the trunk muscles (coefficients of variation between 40-65%) between trials. This could be normal response to body sway. The IP method was less susceptible to false onsets (detecting onsets in the baseline window) 3 vs. 51%. The findings suggest the IP method is robust with large variance in the baseline if the signal to noise ratio is greater than six. In spite of the robustness of the algorithm, the findings would suggest that statistical assessments should be used to target trials for selective visual inspection for subtle trunk muscle onsets.
躯干肌激活的时机已成为理解正常人群和慢性下背痛人群运动的一个重要因素。由于基线噪声或心电（ECG）伪迹，通过肌电图（EMG）信号检测躯干肌起始的预期姿势调整可能存在问题。在不同条件下，休哈特协议或全信号分析可能显示出不同程度的敏感性。在四名受试者（n = 280）中，对疲劳前后五次试验的七块肌肉的表面肌电图进行检查，以确定肌肉活动起始。本研究的目的是检验两种检测方法（休哈特法和综合协议（IP）法）在确定躯干肌起始方面的效果。利用基线幅度的变异性和添加高斯噪声对检测到的起始的影响来测试稳健性。本研究结果表明，在疲劳前后，各试验之间躯干肌存在很大程度的基线差异（变异系数在40 - 65%之间）。这可能是对身体摆动的正常反应。IP方法较少受到假起始（在基线窗口中检测到起始）的影响，分别为3%和51%。研究结果表明，如果信噪比大于6，IP方法在基线存在较大差异时具有稳健性。尽管该算法具有稳健性，但研究结果表明，应使用统计评估来筛选试验，以便对细微的躯干肌起始进行选择性视觉检查。
