Proximal-distal differences in movement smoothness reflect differences in biomechanics

• DOI: 10.1152/jn.00712.2015
• Publication Date: 2016-12-22T02:31:34Z
• Authors: Layne H. Salmond; Andrew D. Davidson; Steven K. Charles
• Keywords: Smoothness; Biomechanics; Smoothing

Smoothness is a hallmark of healthy movement. Past research indicates that smoothness may be side product control strategy minimizes error. However, this not the only reason for smooth movements. Our musculoskeletal system itself contributes to movement smoothness: mechanical impedance (inertia, damping, and stiffness) our limbs joints resists sudden change, resulting in natural smoothing effect. How biomechanics neural interact result an observed level clear. The purpose study 1) characterize wrist rotations, 2) compare it with planar shoulder-elbow (reaching) movements, 3) determine cause differences smoothness. Ten subjects performed reaching movements involving different targets, directions, speeds. We found significantly less than vary direction. To identify causes underlying these observations, we tested number hypotheses bandwidth, signal-dependent noise, speed, anisotropy, duration. simulations revealed proximal-distal reflect biomechanics: greater filters noise more wrist. In contrast, speed were sufficiently large recreate also variation direction appear caused by, or at least correlated with, duration, anisotropy. NEW & NOTEWORTHY This article presents first thorough characterization rotations (flexion-extension radial-ulnar deviation) comparison (shoulder-elbow) determined difference reflects command signal