Department of Biomedical Engineering, The Catholic University of America, Washington, District of Columbia, United States.
Department of Rehabilitation Medicine, Georgetown University, Washington, District of Columbia, United States.
J Neurophysiol. 2024 Dec 1;132(6):1693-1703. doi: 10.1152/jn.00261.2024. Epub 2024 Oct 30.
The objective was to determine whether gravity support for the left arm of right-handed participants would increase left arm use during a three-dimensional (3-D) reaching task in virtual reality. Twelve healthy control participants each completed 630 reaching movements broken into six blocks. The majority of targets were placed close to the midsagittal plane at three heights, and participants were free to use either limb when reaching for targets. The hand had to stay in the target for a prescribed dwell time before the target disappeared. For all reaching tasks within a block, the left arm gravity support was set to either 0% or 75% of full arm support. The blocks also varied in the dwell time (2, 4, or 6 s). The order of blocks was balanced across participants in terms of gravity support level and dwell time. Electromyogram (EMG) level in the left medial deltoid decreased with increasing gravity support ( < 0.001) and was higher for higher targets compared to lower targets ( < 0.001). The odds of using the left arm were 1.95 times higher with gravity support compared to no support ( < 0.001). With gravity support, we expected greater shifts toward the left arm in tasks that were more energetically demanding. This was not the case, as the increased use was evenly distributed across all target heights, and use decreased or remained unchanged with increasing dwell time. Results are discussed relative to current models of limb choice and the potential use of robotic gravity support to overcome learned nonuse in stroke patients. We have shown that gravity support from a robotic exoskeleton increases use of the left arm of right-handed healthy participants. Prior work has shown similar results when movements of one arm are amplified in a virtual environment. The advantage of this approach is the potential to apply the intervention during functional task practice outside of the VR environment or during performance of actual activities of daily living (ADL).
目的是确定对于右利手参与者，给予左手臂重力支撑是否会增加他们在虚拟现实三维（3-D）伸手任务中使用左手臂的次数。12 名健康对照参与者每人完成 630 次伸手动作，分为 6 个组块。大部分目标被放置在中矢状面附近的三个高度，参与者在伸手够目标时可以自由使用任一只手臂。手必须在目标上停留规定的停留时间，然后目标才会消失。在一个组块内的所有伸手任务中，左手臂的重力支撑设置为 0%或 75%的完整手臂支撑。组块也根据停留时间（2、4 或 6 s）的不同而有所变化。根据参与者的重力支撑水平和停留时间，平衡了块的顺序。左三角肌中部的肌电图（EMG）水平随重力支撑的增加而降低（<0.001），且与较低的目标相比，较高的目标的 EMG 水平更高（<0.001）。与无支撑相比，有重力支撑时使用左手的几率高 1.95 倍（<0.001）。有重力支撑时，我们预计在能量需求较高的任务中，手臂会更多地向左侧转移。但事实并非如此，因为增加的使用次数均匀分布在所有目标高度上，且随着停留时间的增加，使用次数减少或保持不变。结果与当前的肢体选择模型以及机器人重力支撑在克服中风患者习得性废用方面的潜在用途相关。我们已经证明，机器人外骨骼提供的重力支撑会增加右利手健康参与者的左手臂使用次数。之前的工作已经表明，当虚拟环境中放大一只手臂的运动时，会产生类似的结果。这种方法的优势在于有可能在虚拟现实环境之外的功能任务练习期间或在进行实际日常生活活动（ADL）期间应用干预措施。
