Shemmell Jonathan, Forner Matthew, Tresilian James R, Riek Stephan, Barry Benjamin K, Carson Richard G
Perception and Motor Systems Laboratory, School of Human Movement Studies, The University of Queensland, Brisbane QLD 4072, Australia.
J Neurophysiol. 2005 Nov;94(5):3046-57. doi: 10.1152/jn.00670.2004. Epub 2005 Jun 8.
In this study we attempted to identify the principles that govern the changes in neural control that occur during repeated performance of a multiarticular coordination task. Eight participants produced isometric flexion/extension and pronation/supination torques at the radiohumeral joint, either in isolation (e.g., flexion) or in combination (e.g., flexion-supination), to acquire targets presented by a visual display. A cursor superimposed on the display provided feedback of the applied torques. During pre- and postpractice tests, the participants acquired targets in eight directions located either 3.6 cm (20% maximal voluntary contraction [MVC]) or 7.2 cm (40% MVC) from a neutral cursor position. On each of five consecutive days of practice the participants acquired targets located 5.4 cm (30% MVC) from the neutral position. EMG was recorded from eight muscles contributing to torque production about the radiohumeral joint during the pre- and posttests. Target-acquisition time decreased significantly with practice in most target directions and at both target torque levels. These performance improvements were primarily associated with increases in the peak rate of torque development after practice. At a muscular level, these changes were brought about by increases in the rates of recruitment of all agonist muscles. The spatiotemporal organization of muscle synergies was not significantly altered after practice. The observed adaptations appear to lead to performances that are generalizable to actions that require both greater and smaller joint torques than that practiced, and may be successfully recalled after a substantial period without practice. These results suggest that tasks in which performance is improved by increasing the rate of muscle activation, and thus the rate of joint torque development, may benefit in terms of the extent to which acquired levels of performance are maintained over time.
在本研究中，我们试图确定在多关节协调任务的重复执行过程中，支配神经控制变化的原则。八名参与者在肱桡关节处产生等长的屈伸和旋前/旋后扭矩，扭矩产生可以单独进行（例如，屈曲），也可以组合进行（例如，屈曲-旋后），以获取视觉显示器呈现的目标。叠加在显示器上的光标提供了所施加扭矩的反馈。在练习前和练习后的测试中，参与者从光标中立位置获取位于八个方向的目标，这些目标距离光标中立位置分别为3.6厘米（20%最大自主收缩[MVC]）或7.2厘米（40%MVC）。在连续五天的练习中，每天参与者都要获取距离中立位置5.4厘米（30%MVC）的目标。在测试前和测试后，从对肱桡关节扭矩产生有贡献的八块肌肉记录肌电图。在大多数目标方向和两种目标扭矩水平下，随着练习，目标获取时间显著减少。这些性能的提高主要与练习后扭矩发展峰值速率的增加有关。在肌肉层面，这些变化是由所有主动肌募集速率的增加引起的。练习后肌肉协同作用的时空组织没有显著改变。观察到的适应性变化似乎导致了这样的表现：这些表现可以推广到需要比所练习的关节扭矩更大或更小的动作中，并且在长时间不练习后仍能成功回忆起来。这些结果表明，通过提高肌肉激活速率进而提高关节扭矩发展速率来改善性能的任务，在保持所获得的性能水平随时间推移的程度方面可能会受益。
