Background

Upper-extremity reactions are part of a whole-body response to counterweight the falling center of mass after unexpected balance loss. Impairments in upper-extremity reactions due to unilateral hemiparesis may contribute to stroke survivors propensity for falling. We aimed to characterize upper-extremity (paretic and non-paretic sides) reactive movements in response to lateral balance perturbations in Persons with Stroke vs. healthy controls.

Methods

Twenty-six subacute persons with stroke and 15 healthy controls were exposed to multidirectional sudden unannounced surface translations in stance. Spatiotemporal parameters of upper- and lower-extremity balance responses to lateral perturbations were analyzed.

Findings

In both groups reactive upper-extremity movement initiation preceded reactive step initiation. In response to a loss of balance toward the paretic side, persons with stroke demonstrated delayed movement initiation of both upper- and lower-extremity compared with healthy controls (In persons with stroke: 234.7 ± 60.0 msec and 227.1 ± 39.6 msec for upper extremities vs. 272.1 ± 59.1 msec for lower-extremity; and in controls: 180.1 ± 39.9 msec and 197.8 ± 61.3 msec for upper-extremities vs. 219.3 ± 40.8 msec for lower-extremity; p = 0.001, Cohen's d's: 0.59–1.03) and a greater abduction excursion in the ipsilateral upper-extremity compared with the contralateral upper-extremity (In persons with stroke: 39.3 ± 23.6 cm vs. 24.9 ± 10.1 cm, respectively; In Controls: 42.6 ± 21.8 cm vs. 29.3 ± 17.3 cm, respectively).

Interpretation

The faster upper-extremity reactive movement reactions compared to reactive step initiation in both persons with stroke and healthy controls suggests that balance recovery is an automatic “reflex-like” response. Delayed upper-extremity reactive reactions in conditions of surface translation toward the non-paretic side in persons with stroke may increase the risk of falls in the direction of the paretic side.

中文翻译：

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脑卒中患者突然失去平衡的上肢反应特征

背景

上肢反应是人体平衡体重下降后重心下降的全身反应的一部分。单侧偏瘫引起的上肢反应障碍可能导致中风幸存者跌倒的倾向。我们的目标是表征卒中患者与健康对照者的横向平衡扰动，从而对上肢（腹部和非腹部）反应性运动进行表征。

方法

26位亚急性卒中患者和15位健康对照者处于多方向突然未宣布的表面平移状态。分析了上肢和下肢平衡对侧向扰动的时空参数。

发现

在两组中，反应性上肢运动开始都在反应性步骤开始之前。为响应朝向顶侧失去平衡，中风患者与健康对照者相比，上肢和下肢运动开始延迟（在中风患者中：上肢234.7±60.0毫秒和227.1±39.6毫秒， 。272.1±59.1毫秒（下肢）；而对照组：180.1±39.9毫秒和197.8±61.3毫秒（上肢），下肢为219.3±40.8毫秒；p  = 0.001，Cohen d：0.59–1.03）和与对侧上肢相比，同侧上肢的外展偏移更大（在中风患者中，分别为39.3±23.6 cm和24.9±10.1 cm；在对照组中：42.6±21.8 cm和29.3±17.3 cm，分别）。

解释

与患有中风的人和健康对照者相比，上肢的反应性运动反应较起步反应更快，这表明平衡恢复是自动的“反射样”反应。在卒中患者向非paretic一侧的表面平移的情况下，上肢反应迟缓，可能会增加其跌落的危险。