Department of Rehabilitation, Exercise, and Nutrition Sciences, University of Cincinnati, Cincinnati, OH, USA.
Center for Cognition, Action, & Perception, Department of Psychology, University of Cincinnati, Cincinnati, OH, USA.
Gait Posture. 2023 Jun;103:133-139. doi: 10.1016/j.gaitpost.2023.05.002. Epub 2023 May 5.
Individuals with stroke commonly demonstrate upper-limb sensorimotor impairments. Upper-limb tasks occur against a background level of postural control and thus require a flexible postural control system to facilitate performance. Anterior precision aiming tasks, for example, benefit from lower medial-lateral (ML) center of pressure (COP) fluctuations (where increased fluctuations erode performance) relative to anterior-posterior (AP) fluctuations (where increased fluctuations do not strongly influence performance). After stroke, individuals may compensate for upper-limb impairments by increasing trunk movement which increases overall COP fluctuations and thus may make it more difficult to modulate COP in a task-sensitive manner.
Do upper-limb task demands modulate COP movement patterns after stroke?
In this cross-sectional study, adults with chronic stroke (n = 23) and unilateral upper-limb impairments were immersed in a virtual environment displaying an anterior target. Participants aimed to maintain the position of a virtual laser pointer (via handheld controller) in the target with each hand. COP was concurrently recorded. Mixed effects models and correlations were used to detect differences in COP patterns between limbs and movement planes and evaluate associations between task performance and COP patterns, respectively.
Participants showed greater COP standard deviation and regularity in the AP compared to the ML direction. The magnitude of difference between AP and ML COP metrics was greater using the nonparetic limb. Task performance was moderately and positively associated with task-sensitive COP patterns (i.e., higher AP:ML ratios of COP metrics) using the paretic upper limb. Participants consistently demonstrated high levels of task performance and task-sensitive COP movement patterns using the nonparetic limb.
Impairments in postural control after stroke may be related to the upper limb used. It is important to recognize the role of directional COP variability and regularity in the context of a task goal after stroke.
患有中风的个体通常表现出上肢感觉运动障碍。上肢任务在背景姿势控制水平上发生，因此需要灵活的姿势控制系统来促进性能。例如，在前部精确瞄准任务中，相对于前后（AP）波动（其中增加的波动不会强烈影响性能），较低的内侧 - 外侧（ML）中心压力（COP）波动（其中增加的波动会侵蚀性能）受益。中风后，个体可能通过增加躯干运动来补偿上肢损伤，这会增加整体 COP 波动，从而可能更难以以任务敏感的方式调节 COP。
上肢任务需求是否会调节中风后的 COP 运动模式？
在这项横断面研究中，患有慢性中风的成年人（n=23）和单侧上肢损伤被沉浸在显示前部目标的虚拟环境中。参与者旨在使用手持控制器保持虚拟激光笔在目标中的位置。同时记录 COP。混合效应模型和相关性用于检测 COP 模式在四肢和运动平面之间的差异，并分别评估任务性能与 COP 模式之间的关联。
参与者在 AP 方向上的 COP 标准差和规律性大于 ML 方向。非麻痹侧 COP 指标的 AP 与 ML 之间的差异幅度更大。使用瘫痪上肢，任务性能与 COP 模式的任务敏感性呈中度正相关（即，AP：ML COP 指标的比值较高）。参与者使用非麻痹肢体始终表现出较高的任务性能和任务敏感的 COP 运动模式。
中风后姿势控制的损伤可能与使用的上肢有关。在中风后，重要的是要认识到 COP 变异性和规律性的方向在任务目标的背景下的作用。
