Aix-Marseille University, UMR 6233 Human Movement Sciences Institute, 163 Avenue de Luminy, 13288 Marseille Cedex 09, France.
Neuroscience. 2011 Dec 1;197:233-41. doi: 10.1016/j.neuroscience.2011.09.020. Epub 2011 Sep 16.
Achieving movements with accuracy despite the inevitable variability of the neuromuscular mechanisms is an important everyday life problem, which has to be solved for the production of any adapted motor act, such as walking, writing, catching, or pointing. To solve this problem when we have to make goal-directed movements as fast as possible, we systematically increase movement time when accuracy requirements increase, a ubiquitous phenomenon qualified as speed-accuracy trade-off. It has been proposed that this speed-accuracy trade-off reflects an optimal compromise between speed and accuracy in the presence of biological noise and that increasing movement speed inevitably leads to decreased motor accuracy. However, the recent finding that muscle cocontraction improves movement accuracy may challenge this view and begs the question of how movement speed control and cocontraction control coexist. Here, we show that humans are in fact able to move faster while preserving movement accuracy, by using a strategy where muscles are cocontracted around the joint. As this energetically costly cocontraction strategy was not naturally used, this result has two important implications. It first demonstrates that a speed modulation strategy is preferred to a cocontraction strategy for fast, accurate movements, and it also suggests that energy economy prevents us to execute accurate movements as fast as we could do. Consequently, we propose that the mechanisms underlying the speed-accuracy trade-off are more complex than previously thought, and suggest the existence of a previously unknown speed-energy-accuracy trade-off for goal-directed movements.
尽管神经肌肉机制不可避免地存在变异性，但要实现精确的运动仍然是一个重要的日常生活问题，这对于产生任何适应运动行为（如行走、书写、捕捉或指向）都是必要的。为了解决这个问题，当我们必须尽快进行目标导向运动时，我们会根据精度要求增加运动时间，这是一种普遍存在的现象，被称为速度-精度权衡。有人提出，这种速度-精度权衡反映了在存在生物噪声的情况下速度和精度之间的最佳折衷，并且增加运动速度不可避免地会导致运动精度降低。然而，最近发现肌肉协同收缩可以提高运动精度，这可能会挑战这一观点，并引发一个问题，即运动速度控制和协同收缩控制如何共存。在这里，我们通过使用一种在关节周围协同收缩肌肉的策略，表明人类实际上能够在保持运动精度的同时更快地运动。由于这种能量消耗高的协同收缩策略不是自然使用的，因此这个结果有两个重要的含义。它首先证明了在快速、准确的运动中，速度调制策略优先于协同收缩策略，也表明能量经济性阻止我们以最快的速度执行准确的运动。因此，我们提出速度-精度权衡的机制比以前想象的更为复杂，并提出对于目标导向运动存在一个以前未知的速度-能量-精度权衡。
