Lavender S A, Tsuang Y H, Andersson G B
Department of Orthopedic Surgery, Rush-Presbyterian-St Luke's Medical Center, Chicago, IL 60612.
Ergonomics. 1993 Oct;36(10):1145-57. doi: 10.1080/00140139308967985.
Previous studies of twisting have revealed substantial cocontraction of agonist and antagonist muscles within the torso when torsional moments are generated. The objective of the current study was to quantify the activations and cocontraction of eight trunk muscles as subjects maintained an axially rotated trunk posture and resisted external applied bending moments. Ten subjects twisted their torsos 25 degrees to the right (clockwise) and resisted 20 and 40 Nm bending moments from 12 directions. The moment directions were in a transverse plane and labelled clockwise as viewed from above, ranging from 0 degrees (mid-saggital, anterior) to 330 degrees, in 30 degrees increments. RMS EMG amplitude data were collected using surface electrodes and normalized to maximal voluntary contractions. Significant changes were observed in the muscle responses due to the interaction of the moment direction and moment magnitude for six of the eight muscles tested. Comparison of the present data with that collected previously in neutral postures indicated: (1) a large increase in the activation levels of the right erector spinae and the left external oblique muscles; and (2) a counter-clockwise shift in the moment direction at which the peak activation of these same muscles occurs. Analysis of the relative activation levels (RALs), constructed from the NEMG data to quantify the cocontraction, indicated that the changes in cocontraction were more robust in response to changes in the bending moment's direction as opposed to changes in bending moment's magnitude.
先前关于扭转的研究表明，当产生扭转力矩时，躯干内的主动肌和拮抗肌会发生显著的共同收缩。本研究的目的是量化八块躯干肌肉的激活和共同收缩情况，此时受试者保持轴向旋转的躯干姿势并抵抗外部施加的弯曲力矩。十名受试者将躯干向右扭转25度（顺时针），并抵抗来自12个方向的20和40牛米的弯曲力矩。力矩方向在横向平面内，从上方看按顺时针方向标记，范围从0度（中矢状面，前方）到330度，以30度为增量。使用表面电极收集均方根肌电图幅度数据，并将其归一化为最大自主收缩。在所测试的八块肌肉中的六块中，由于力矩方向和力矩大小的相互作用，观察到肌肉反应有显著变化。将当前数据与之前在中立姿势下收集的数据进行比较表明：（1）右侧竖脊肌和左侧腹外斜肌的激活水平大幅增加；（2）这些相同肌肉发生峰值激活时的力矩方向逆时针偏移。根据归一化肌电图数据构建的相对激活水平（RAL）分析用于量化共同收缩，结果表明，与弯曲力矩大小的变化相比，共同收缩的变化对弯曲力矩方向的变化反应更强烈。
