Greve Christian, Hortobàgyi Tibor, Bongers Raoul M
Center for Human Movement Science, University of Groningen, University Medical Center Groningen, Groningen, The Netherland.
Center for Human Movement Science, University of Groningen, University Medical Center Groningen, Groningen, The Netherland; Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle-upon-Tyne, United Kingdom.
PLoS One. 2015 May 13;10(5):e0127017. doi: 10.1371/journal.pone.0127017. eCollection 2015.
Healthy humans are able to place light and heavy objects in small and large target locations with remarkable accuracy. Here we examine how dexterity demand and physical demand affect flexibility in joint coordination and end-effector kinematics when healthy young adults perform an upper extremity reaching task. We manipulated dexterity demand by changing target size and physical demand by increasing external resistance to reaching. Uncontrolled manifold analysis was used to decompose variability in joint coordination patterns into variability stabilizing the end-effector and variability de-stabilizing the end-effector during reaching. Our results demonstrate a proportional increase in stabilizing and de-stabilizing variability without a change in the ratio of the two variability components as physical demands increase. We interpret this finding in the context of previous studies showing that sensorimotor noise increases with increasing physical demands. We propose that the larger de-stabilizing variability as a function of physical demand originated from larger sensorimotor noise in the neuromuscular system. The larger stabilizing variability with larger physical demands is a strategy employed by the neuromuscular system to counter the de-stabilizing variability so that performance stability is maintained. Our findings have practical implications for improving the effectiveness of movement therapy in a wide range of patient groups, maintaining upper extremity function in old adults, and for maximizing athletic performance.
健康的人能够以极高的准确性将轻、重物体放置在大小不同的目标位置。在此，我们研究当健康的年轻人执行上肢伸展任务时，灵活性需求和体力需求如何影响关节协调和末端执行器运动学的灵活性。我们通过改变目标大小来操纵灵活性需求，并通过增加伸展的外部阻力来操纵体力需求。采用非受控流形分析将关节协调模式的变异性分解为在伸展过程中稳定末端执行器的变异性和使末端执行器不稳定的变异性。我们的结果表明，随着体力需求的增加，稳定和不稳定变异性成比例增加，而两个变异性成分的比例不变。我们结合先前的研究来解释这一发现，这些研究表明感觉运动噪声会随着体力需求的增加而增加。我们提出，作为体力需求函数的更大的不稳定变异性源于神经肌肉系统中更大的感觉运动噪声。随着体力需求增加而更大的稳定变异性是神经肌肉系统采用的一种策略，以对抗不稳定变异性，从而保持运动表现的稳定性。我们的发现对于提高广泛患者群体的运动治疗效果、维持老年人的上肢功能以及最大化运动表现具有实际意义。
