Amell T K, Kumar S, Narayan Y, Coury H C
Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada.
Ergonomics. 2000 Apr;43(4):512-27. doi: 10.1080/001401300184387.
The aim of the experiment was to determine the impact of axial trunk rotation and arm position on upper extremity adduction force and muscle activity. Ten healthy male subjects performed graded maximum voluntary contractions under isometric conditions in seven upper extremity positions and three trunk postures (neutral and 90 degrees left/right rotated) in a simulated manual materials handling task. A custom built lightweight force-measuring device was held between the palmar surfaces of the hands and subjects compressed the lateral surfaces of the device. Muscle activity was recorded bilaterally over the muscle bellies of the anterior deltoid, the long head of the biceps brachii and over the flexor carpi radialis. The activity of the right pectoralis major was also recorded unilaterally. Descriptive, multivariate analysis of variance (MANOVA) and post-hoc Scheffé comparisons were performed on the mean and peak force as well as the EMG [electromyographic] data. Further analysis was performed on the force-EMG relationship at 20% intervals of maximum voluntary contraction (force). Both upper extremity adduction force and EMG were significantly affected by position (p<0.01) but not by trunk rotation. The muscle activity increased and force decreased with flexion of the upper extremity. Pearson correlation coefficients between force and EMG were low. The biceps and flexors were the most active muscles depending upon upper extremity position, and the right pectoralis major muscle activity expressed the highest correlation with force. The present findings confirm earlier hypotheses that upper extremity adduction strength is not significantly affected by trunk rotation.
该实验的目的是确定躯干轴向旋转和手臂位置对上肢内收力及肌肉活动的影响。十名健康男性受试者在模拟人工搬运任务中，于七种上肢位置和三种躯干姿势（中立位以及向左/向右旋转90度）下，在等长条件下进行分级最大自主收缩。一个定制的轻质测力装置夹在双手掌面之间，受试者挤压该装置的侧面。双侧记录三角肌前部、肱二头肌长头和桡侧腕屈肌肌腹的肌肉活动。还单侧记录了右侧胸大肌的活动。对平均力、峰值力以及肌电图（EMG）数据进行了描述性、多变量方差分析（MANOVA）和事后Scheffé比较。在最大自主收缩（力）的20%间隔处，对力-肌电图关系进行了进一步分析。上肢内收力和肌电图均受位置显著影响（p<0.01），但不受躯干旋转影响。随着上肢屈曲，肌肉活动增加而力减小。力与肌电图之间的Pearson相关系数较低。根据上肢位置不同，肱二头肌和屈肌是最活跃的肌肉，且右侧胸大肌的肌肉活动与力的相关性最高。本研究结果证实了早期的假设，即躯干旋转对上肢内收力量无显著影响。
