Weaver Tyler B, Glinka Michal N, Laing Andrew C
Injury Biomechanics and Aging Laboratory, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada.
Injury Biomechanics and Aging Laboratory, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada.
J Biomech. 2017 Feb 28;53:90-96. doi: 10.1016/j.jbiomech.2017.01.003. Epub 2017 Jan 6.
While stooping and crouching postures are critical for many activities of daily living, little is known about the balance control mechanisms employed during these postures. Accordingly, the purpose of this study was to characterize the mechanisms driving net center of pressure (COP) movement across three postures (standing, stooping, and crouching) and to investigate if control in each posture was influenced by time.
Ten young adults performed the three postures for 60s each. Kinetic signals were collected via a force platform under each foot. To quantify mechanisms of control, correlations (Correl) were calculated between the left and right COP trajectories in the anterior-posterior (AP) and medio-lateral (ML) directions. To examine the potential effects of time on balance control strategies, outcomes during the first 30s were compared to the last 30s.
Correl values did not differ across postures (AP: p = 0.395; ML: p = 0.647). Further, there were no main effects of time on Correl (AP: p = 0.976; ML: p = 0.105). A significant posture-time interaction was observed in the ML direction (p = 0.045) characterized by 35% decreases in Correl over time for stooping (p = 0.022).
The dominant controllers of sway (i.e., AP: ankle plantar/dorsi flexors; ML: hip load/unload mechanism) are similar across quiet stance stooping, and crouching. Changes in ML control strategies over time suggests that fatigue could affect prolonged stooping more so than crouching or standing.
虽然弯腰和蹲姿对于许多日常生活活动至关重要，但对于这些姿势下所采用的平衡控制机制却知之甚少。因此，本研究的目的是描述驱动压力中心（COP）在三种姿势（站立、弯腰和蹲姿）间移动的机制，并研究每种姿势下的控制是否受时间影响。
10名年轻成年人分别进行这三种姿势，每种姿势持续60秒。通过每只脚下的测力平台收集动力学信号。为了量化控制机制，计算前后（AP）和内外侧（ML）方向上左右COP轨迹之间的相关性（Correl）。为了研究时间对平衡控制策略的潜在影响，将前30秒的结果与后30秒的结果进行比较。
相关性值在不同姿势间无差异（AP：p = 0.395；ML：p = 0.647）。此外，时间对相关性没有主要影响（AP：p = 0.976；ML：p = 0.105）。在ML方向观察到显著的姿势 - 时间交互作用（p = 0.045），其特征是弯腰时相关性随时间下降35%（p = 0.022）。
在安静站立、弯腰和蹲姿中，摆动的主要控制因素（即AP：踝关节跖屈/背屈肌；ML：髋关节加载/卸载机制）相似。ML控制策略随时间的变化表明，疲劳对长时间弯腰的影响可能比对蹲姿或站立的影响更大。
