Stokes I A, Rush S, Moffroid M, Johnson G B, Haugh L D
Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington.
Spine (Phila Pa 1976). 1987 Oct;12(8):770-6. doi: 10.1097/00007632-198710000-00011.
The integrated surface electromyogram (IEMG) of the lumbar erectores spinae and the torque generated were simultaneously recorded from 27 healthy subjects in the standing posture while they pulled isometrically against resistance provided by a harness around the shoulders. The IEMG-torque ratio (efficiency of electrical activity, or EEA) was used to characterize each subject. Individual recordings showed evidence of nonlinearity of the IEMG-torque relationship in that a statistically better fit to experimental recordings was obtained by using two straight lines with a breakpoint between them. However, with repeated testing, the gradients of these two lines were more variable than the slope of the single straight line fitted to the entire recording. The slope of the best fit line (EEA) was less for recordings made during torque decrease than for increasing-torque recordings. This also showed as a "hysteresis" pattern in the recordings. The coefficient of variability (within subjects) of the EEA was greater in day-to-day testing (24%) than with repeated pulls at the same testing session (14%). This was similar to variability of the maximum generated torque. About 25% of the variability between subjects was found to be due to anthropometric differences. The residual variability of the relationship would limit the accuracy of IEMG as a measure of muscular effort under changing torque conditions. However, the EEA may be useful for characterizing muscle performance, especially when maximum effort cannot be achieved.
对27名健康受试者站立姿势时的腰椎竖脊肌表面肌电图（IEMG）和产生的扭矩进行同步记录，受试者通过对抗肩部束带提供的阻力进行等长收缩。IEMG-扭矩比（电活动效率，即EEA）用于描述每个受试者的特征。个体记录显示IEMG-扭矩关系存在非线性，即使用两条直线（中间有一个断点）对实验记录进行统计拟合时，拟合效果更好。然而，随着重复测试，这两条直线的斜率比拟合整个记录的单一直线的斜率变化更大。扭矩下降时记录的最佳拟合线（EEA）的斜率小于扭矩增加时记录的斜率。这在记录中也表现为一种“滞后”模式。EEA的（受试者内）变异系数在日常测试中（24%）大于在同一测试时段内重复拉伸时（14%）。这与最大产生扭矩的变异性相似。发现约25%的受试者间变异性是由于人体测量学差异所致。这种关系的残余变异性会限制IEMG在变化扭矩条件下作为肌肉用力测量指标的准确性。然而，EEA可能有助于描述肌肉性能，特别是在无法达到最大用力时。
