1 McGill University, Montreal, Quebec, Canada.
2 Jewish Rehabilitation Hospital Site, Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal, Quebec, Canada.
Neurorehabil Neural Repair. 2018 Feb;32(2):175-186. doi: 10.1177/1545968318760725.
Kinematic redundancy of the human body provides abundant movement patterns to accomplish the same motor goals (motor equivalence). Compensatory movement patterns such as excessive trunk displacement in stroke subjects during reaching can be viewed as a consequence of the motor equivalent process to accomplish a task despite limited available ranges in some joints. However, despite compensations, the ability to adapt reaching performance when perturbations occur may still be limited when condition-specific changes of joint angles are required. We addressed this hypothesis in individuals with and without stroke for reaching a target placed beyond arm reach in standing while flexing the hips (free-hip condition). In randomly selected trials, hip flexion was unexpectedly blocked, forcing subjects to take a step (blocked-hip condition). In additional trials, subjects took an intentional step while reaching the target (intentional-step condition). In blocked-hip trials, healthy subjects maintained smooth and precise endpoint trajectories by adapting temporal and spatial interjoint coordination to neutralize the effect of the perturbation. However, the ability to produce motor equivalent solutions was reduced in subjects with stroke, evidenced by substantial overshoot errors in endpoint position, reduced movement smoothness and less adaptive elbow-shoulder interjoint coordination. Movement adaptability was more limited in stroke subjects who used more compensatory movements for unperturbed reaching. Results suggest that subjects with mild-to-moderate stroke only partially adapted arm joint movements to maintain reaching performance. Therapeutic efforts to enhance the ability of individuals with stroke to find a larger number of task-relevant motor solutions (adaptability) may improve upper limb recovery.
人体运动学的冗余为完成相同的运动目标（运动等效）提供了丰富的运动模式。在中风患者进行伸展运动时，过度的躯干位移等代偿运动模式可以被视为运动等效过程的结果，尽管某些关节的可用范围有限，但仍能完成任务。然而，尽管有代偿作用，当需要特定条件下的关节角度变化时，当出现干扰时，适应伸展表现的能力可能仍然有限。我们针对站立时髋关节弯曲（自由髋关节条件）伸展至手臂不可及的目标的有和无中风的个体进行了研究。在随机选择的试验中，髋关节弯曲被意外地阻断，迫使受试者迈出一步（阻断髋关节条件）。在其他试验中，受试者在伸展到目标的同时故意迈出一步（故意迈出一步条件）。在阻断髋关节的试验中，健康受试者通过调整时空关节间协调来适应干扰，从而保持平滑和精确的末端轨迹。然而，中风患者产生运动等效解的能力降低，表现在末端位置的明显过冲误差、运动平滑度降低和肘部-肩部关节间协调适应性降低。在未受干扰的伸展运动中使用更多代偿运动的中风患者，运动适应性更有限。结果表明，轻度至中度中风患者仅部分调整手臂关节运动以维持伸展表现。增强中风患者寻找更多与任务相关的运动解决方案的能力（适应性）的治疗努力可能会改善上肢的恢复。
