Yamazaki Y, Ohkuwa T, Itoh H, Suzuki M
Department of Health and Physical Education, Nagoya Institute of Technology, Japan.
Brain Res Bull. 1994;34(6):587-93. doi: 10.1016/0361-9230(94)90144-9.
Seven normal subjects performed elbow extensions as rapidly as possible from an initial position to a visually defined target at 36 degrees in amplitude. In electromyograms, the reciprocal activation of the agonist and then antagonist bursts was always followed by simultaneous activation of the antagonistic muscles, i.e., coactivation. Instructions added to perform extensions "as rapidly as possible" changed coactivation; the command to "strongly fix the upper arm at the target" increased coactivation, whereas "relax immediately after the start of movement" made coactivation almost disappear. However, basic features of reciprocal activation remained the same. Other instructions given also changed coactivation on initiation and termination, while reciprocal activation was relatively unaltered. When subjects were encouraged to "relax immediately after the start of movement, but fix the upper arm quickly after attaining the target," coactivation initiated shortly after reaching the target (< 200 ms). Following the instruction to "relax the upper arm quickly after attaining the target," coactivation terminated rapidly after reaching the target (< 280 ms). The results show that instructions serve to change amplitude and timing of coactivation while keeping reciprocal activation relatively unaltered, suggesting that coactivation is controlled independently of reciprocal activation during rapid goal-directed movements.
七名正常受试者以尽可能快的速度从初始位置进行肘部伸展，幅度达到视觉定义的36度目标。在肌电图中，主动肌爆发和随后拮抗肌爆发的交替激活之后总是伴随着拮抗肌的同时激活，即共同激活。添加“尽可能快地”进行伸展的指令改变了共同激活；“在目标位置强烈固定上臂”的指令增加了共同激活，而“运动开始后立即放松”使共同激活几乎消失。然而，交替激活的基本特征保持不变。给出的其他指令也改变了起始和终止时的共同激活，而交替激活相对未改变。当鼓励受试者“运动开始后立即放松，但达到目标后迅速固定上臂”时，共同激活在达到目标后不久（<200毫秒）开始。遵循“达到目标后迅速放松上臂”的指令，共同激活在达到目标后迅速终止（<280毫秒）。结果表明，指令有助于改变共同激活的幅度和时间，同时保持交替激活相对不变，这表明在快速的目标导向运动中，共同激活是独立于交替激活进行控制的。
