Department of Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America.
Department of Computer Science, University of Colorado, Boulder, Colorado, United States of America.
PLoS Comput Biol. 2024 May 31;20(5):e1012169. doi: 10.1371/journal.pcbi.1012169. eCollection 2024 May.
On any given day, we make countless reaching movements to objects around us. While such ubiquity may suggest uniformity, each movement's speed is unique-why is this? Reach speed is known to be influenced by accuracy; we slow down to sustain high accuracy. However, in other forms of movement like walking or running, metabolic cost is often the primary determinant of movement speed. Here we bridge this gap and ask: how do metabolic cost and accuracy interact to determine speed of reaching movements? First, we systematically measure the effect of increasing mass on the metabolic cost of reaching across a range of movement speeds. Next, in a sequence of three experiments, we examine how added mass affects preferred reaching speed across changing accuracy requirements. We find that, while added mass consistently increases metabolic cost thereby leading to slower metabolically optimal movement speeds, self-selected reach speeds are slower than those predicted by an optimization of metabolic cost alone. We then demonstrate how a single model that considers both accuracy and metabolic costs can explain preferred movement speeds. Together, our findings provide a unifying framework to illuminate the combined effects of metabolic cost and accuracy on movement speed and highlight the integral role metabolic cost plays in determining reach speed.
在任何一天，我们都会无数次伸手去拿身边的物体。虽然这种普遍性可能表明动作的一致性，但每个动作的速度都是独特的——这是为什么呢？众所周知，伸手的速度会受到准确性的影响；为了保持较高的准确性，我们会放慢速度。然而，在其他形式的运动中，如步行或跑步，代谢成本通常是决定运动速度的主要因素。在这里，我们弥合了这一差距，并提出了以下问题：代谢成本和准确性如何相互作用来决定伸手动作的速度？首先，我们系统地测量了在一系列运动速度下增加质量对伸手代谢成本的影响。接下来，在三个实验序列中，我们研究了附加质量如何在不断变化的准确性要求下影响首选伸手速度。我们发现，虽然增加的质量会持续增加代谢成本，从而导致代谢最佳速度变慢，但自我选择的伸手速度比仅通过代谢成本优化预测的速度要慢。然后，我们证明了如何通过同时考虑准确性和代谢成本的单一模型来解释首选运动速度。总之，我们的研究结果提供了一个统一的框架，阐明了代谢成本和准确性对运动速度的综合影响，并强调了代谢成本在确定伸手速度方面的重要作用。
