Yamazaki Y, Itoh H, Ohkuwa T
Department of Health and Physical Education, Nagoya Institute of Technology, Japan.
Brain Res Bull. 1995;38(3):285-95. doi: 10.1016/0361-9230(95)00101-j.
Normal human subjects performed extensions of the elbow from an initial position to a visually defined target as rapidly and accurately as possible at different angular amplitudes (9 degrees-54 degrees) and at a constant amplitude (36 degrees) under various additional instructions. Joint angle, angular acceleration, and electromyograms (EMGs) from agonist (triceps lateralis), antagonist (biceps), and antebrachial muscles were recorded. EMGs of the antagonistic muscles showed reciprocal activation of the first triceps, and then the biceps, which was followed by the second triceps activation and coactivation of both muscles. Movement amplitude changed the reciprocal activation, whereas the coactivation was unaltered. Additional instructions changed the coactivation in amplitude, initiation, and termination, whereas the reciprocal activation was relatively preserved. Under these conditions, EMGs of antebrachial muscles were always linked with the coactivation in amplitude and timing but not with the reciprocal activation. The linkage suggests that antebrachial muscle activation serves as an indicator of the coactivation. From the indicator, we infer that the coactivation initiates from the beginning of the rapid movements and changes during the dynamic movement phase.
正常人类受试者在不同角度幅度（9度至54度）以及在恒定幅度（36度）下，按照各种额外指示，尽可能快速且准确地将肘部从初始位置伸展至视觉定义的目标位置。记录了关节角度、角加速度以及来自主动肌（外侧肱三头肌）、拮抗肌（肱二头肌）和前臂肌肉的肌电图（EMG）。拮抗肌的肌电图显示，首先是肱三头肌的交互激活，然后是肱二头肌，接着是第二次肱三头肌激活以及两块肌肉的共同激活。运动幅度改变了交互激活，而共同激活未改变。额外指示改变了共同激活在幅度、起始和终止方面的情况，而交互激活相对保持不变。在这些条件下，前臂肌肉的肌电图在幅度和时间上总是与共同激活相关联，而与交互激活无关。这种关联表明前臂肌肉激活作为共同激活的一个指标。从这个指标来看，我们推断共同激活从快速运动开始时就启动，并在动态运动阶段发生变化。
