Background

Reach-to-grasp responses following balance perturbations are important to fall prevention but are often ineffective in older adults. The ability to shift attention from an ongoing cognitive task to balance related processes has been shown to influence reach-to-grasp effectiveness in older adults. However, the added influence of stress and anxiety - known to negatively affect attention shifting ability - has not yet been explored in relation to recovery from balance perturbations. Given that fear and anxiety over falling is a key fall risk factor, an understanding of how such a negative mental state may affect postural reactions is important. This study aimed to investigate the effect of varied induced emotional states on reach-to-grasp balance responses in older adults.

Methods

Healthy older adults (mean age 70.5 ± 5.38 years) stood laterally between 2 handrails with contact sensors. A safety harness with an integrated loadcell was worn to prevent falls and measure the amount of harness assistance (expressed as percent body weight). With instructions to grasp one rail to restore balance, participants' balance was laterally disturbed using surface translations under three randomized conditions: no cognitive task, neutral (verb generation) task, and mental stress task with negative prompts (paced auditory serial addition). The primary outcome was frequency of protective grasps. Secondary outcomes included frequency of harness assistance during trials with grasp errors as well as wrist movement time, trajectory distance, and peak velocity.

Results

Perceived level of distress was highest for the mental stress task compared to no task (p < 0.001) and neutral task conditions (p = 0.008). The mental stress task resulted in the lowest percentage of protective grasps (p < 0.001) in response to balance perturbations. Closer examination of trials that resulted in grasp errors (i.e., collisions or overshoots), revealed increased harness assistance and reduced peak velocity of wrist movement (p < 0.001) under the mental stress condition compared to grasp errors that occurred under the no task or neutral task condition.

Discussion and conclusion

Distressing mental thoughts immediately prior to a balance perturbation lead to reduced effectiveness in reach-to-grasp balance responses compared to no or neutral cognitive tasks and should be considered as a possible fall risk factor.

中文翻译：

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检查精神压力对老年人平衡扰动反应的影响

背景

平衡扰动后的伸手可及的反应对于预防跌倒很重要，但在老年人中通常无效。将注意力从正在进行的认知任务转移到平衡相关过程的能力已被证明会影响老年人的“伸手可及”的有效性。然而，压力和焦虑的附加影响——已知会对注意力转移能力产生负面影响——尚未与从平衡扰动中恢复有关的问题进行探索。鉴于跌倒的恐惧和焦虑是跌倒的关键风险因素，了解这种消极的精神状态如何影响姿势反应很重要。本研究旨在调查不同诱发的情绪状态对老年人伸手可及的平衡反应的影响。

方法

健康的老年人（平均年龄 70.5 ± 5.38 岁）横向站在两个带有接触传感器的扶手之间。佩戴带有集成称重传感器的安全带以防止跌倒并测量安全带辅助量（以体重百分比表示）。在指示抓住一根轨道以恢复平衡的情况下，参与者的平衡在三种随机条件下使用表面平移受到横向干扰：无认知任务、中性（动词生成）任务和带有负面提示的精神压力任务（有节奏的听觉连续添加）。主要结果是保护性抓握的频率。次要结果包括在试验中出现抓握错误的线束辅助频率以及手腕运动时间、轨迹距离和峰值速度。

结果

与无任务 ( p  < 0.001) 和中性任务条件 ( p  = 0.008)相比，精神压力任务的痛苦感知水平最高。精神压力任务导致 响应平衡扰动的保护性抓握百分比最低 ( p < 0.001)。对导致抓握错误（即碰撞或过冲）的试验进行仔细检查，发现 与无任务或中立状态下发生的抓握错误相比，精神压力条件下的安全带辅助增加和手腕运动峰值速度降低 ( p < 0.001)任务条件。

讨论与结论

与没有认知任务或中性认知任务相比，在平衡扰动之前立即出现令人痛苦的心理想法会导致达到掌握平衡反应的有效性降低，并且应被视为可能的跌倒风险因素。