Smeets J B, Erkelens C J, Denier van der Gon J J
Vakgroep Medische en Fysiologische Fysica, Rijksuniversiteit te Utrecht, The Netherlands.
Exp Brain Res. 1990;81(2):303-12. doi: 10.1007/BF00228120.
Subjects made fast goal-directed elbow flexion movements against an inertial load. Target distance was 8 or 16 cm, randomly chosen. To exert a force in the direction of the movement subjects had to activate flexors of both shoulder and elbow, but shoulder flexors did not change appreciably in length during the movement. In 20% of the trials the inertial load was increased or decreased without knowledge of the subjects. Until 90-110 ms after the onset of the agonist muscle activity (about 65-85 ms after the start of movement) EMG activity was very similar in all conditions tested. The changes that occurred in the EMG from that moment on were effectively a later cessation of the agonist activity and a later start of the antagonist activity if the load was increased unexpectedly. If the load was reduced unexpectedly, the agonist activity ceased earlier and the antagonist activity began earlier. The latency at which EMGs started to change was the same for muscles around shoulder and elbow, for agonists and antagonists and for both distances. All adjustments had the same latency (37 ms) relative to the point where the angular velocity of the elbow in the unexpectedly loaded movements differed by 0.6 rad/s from the expected value. We discuss why simple reflex- or servo-mechanisms cannot account for the measured EMG changes. We conclude that appropriate adjustments of motor programmes for fast goal-directed arm movements start within 40 ms of the detection of misjudgment of load.
受试者针对惯性负荷进行快速的目标导向性肘部屈曲运动。目标距离为8或16厘米，随机选择。为了在运动方向上施加力，受试者必须激活肩部和肘部的屈肌，但肩部屈肌在运动过程中长度变化不明显。在20%的试验中，在受试者不知情的情况下增加或减少惯性负荷。在激动剂肌肉活动开始后90 - 110毫秒内（大约在运动开始后65 - 85毫秒），所有测试条件下的肌电图活动都非常相似。从那一刻起，肌电图发生的变化实际上是，如果负荷意外增加，激动剂活动稍后停止，拮抗剂活动稍后开始。如果负荷意外减少，激动剂活动更早停止，拮抗剂活动更早开始。肩部和肘部周围的肌肉、激动剂和拮抗剂以及两种距离下，肌电图开始变化的潜伏期相同。相对于意外加载运动中肘部角速度与预期值相差0.6弧度/秒的点，所有调整都具有相同的潜伏期（37毫秒）。我们讨论了为什么简单的反射或伺服机制不能解释所测量的肌电图变化。我们得出结论，对于快速的目标导向性手臂运动，运动程序的适当调整在检测到负荷判断错误后的40毫秒内开始。
