McGill S M
Department of Kinesiology, University of Waterloo, Ontario, Canada.
J Orthop Res. 1991 Jan;9(1):91-103. doi: 10.1002/jor.1100090112.
This study focused on the electromyographic activity of the trunk musculature, given the well-documented link between occupational twisting and the increased incidence of low back pain. Ten men and 15 women volunteered for this study, in which several aspects of muscle activity were examined. The first aspect assessed the myoelectric relationships during isometric exertions. There was great variability in this relationship between muscles and between subjects. Further, the myoelectric activity levels (normalized to maximal electrical activity) obtained from nontwist activities were not maximal despite maximal efforts to generate axial torque (e.g., rectus abdominis, maximum voluntary contraction; 22% external oblique, 52%; internal oblique, 55%; latissimus dorsi, 74%; upper erector spinae [T9], 61%; lower erector spinae [L3], 33%). In the second aspect of the study, muscle activity was examined during dynamic axial twist trials conducted at a velocity of 30 and 60 degrees/s. The latissimus dorsi and external oblique appeared to be strongly involved in the generation of axial torque throughout the twist range and activity in the upper erector spinae displayed a strong link with axial torque and direction of twist, even though they have no mechanical potential to contribute axial torque, suggesting a stabilization role. The third aspect of the study was comprised of the formulation of a model consisting of a three-dimensional pelvis, rib cage, and lumbar vertebrae and driven from kinematic measures of axial twist and muscle electromyograms. The relatively low levels of normalized myoelectric activity during maximal twisting efforts coupled with large levels of agonist-antagonist cocontraction caused the model to severely underpredict measured torques (e.g., 14 Nm predicted for 91 Nm measured). Such dominant coactivity suggests that stabilization of the joints during twisting is far more important to the lumbar spine than production of large levels of axial torque.
鉴于职业性扭转与下背痛发病率增加之间已得到充分证明的联系，本研究聚焦于躯干肌肉组织的肌电活动。10名男性和15名女性自愿参与本研究，其中对肌肉活动的几个方面进行了检查。第一个方面评估了等长用力时的肌电关系。肌肉之间以及受试者之间的这种关系存在很大差异。此外，尽管竭尽全力产生轴向扭矩，但从非扭转活动中获得的肌电活动水平（相对于最大电活动进行归一化）并非最大（例如，腹直肌，最大自主收缩；腹外斜肌22%，腹内斜肌52%，背阔肌74%，上竖脊肌[T9]61%，下竖脊肌[L3]33%）。在研究的第二个方面，在以30度/秒和60度/秒的速度进行的动态轴向扭转试验期间检查肌肉活动。背阔肌和腹外斜肌在整个扭转范围内似乎都强烈参与轴向扭矩的产生，而上竖脊肌的活动与轴向扭矩和扭转方向显示出很强的联系，尽管它们没有产生轴向扭矩的机械潜力，这表明其具有稳定作用。研究的第三个方面包括构建一个由三维骨盆、胸廓和腰椎组成的模型，并根据轴向扭转的运动学测量和肌肉肌电图来驱动该模型。在最大扭转用力期间相对较低的归一化肌电活动水平，加上高水平 agonist - antagonist 共收缩，导致该模型严重低估了测量到 的扭矩（例如，测量到91 Nm，预测为14 Nm）。这种占主导地位的共同活动表明，扭转过程中关节的稳定对腰椎比产生大量轴向扭矩更为重要。
