Kal Elmar C, Young William R, Ellmers Toby J
College of Health, Medicine and Life Sciences, Division of Physiotherapy, Brunel University London, UK; Centre for Cognitive Neuroscience, Brunel University London, UK.
School of Sport and Health Sciences, University of Exeter, UK.
Hum Mov Sci. 2022 Apr;82:102933. doi: 10.1016/j.humov.2022.102933. Epub 2022 Feb 5.
Older adults rely increasingly on conscious processes to control balance. While this could be in response to age-related declines in balance capacity, it is unclear whether such strategy is adaptive or not. We investigated whether balance capacity modified the effects of conscious movement processing (CMP) on postural control in older adults. Forty-seven older adults (M = 74.8, range = 61-88) completed 60-s, narrow-stance balance trials on a force platform, under conditions designed to increase (high-CMP; through movement-monitoring instructions) or reduce conscious processing (low-CMP; distraction task). Balance capacity was operationalised as a composite score of Berg Balance Scale and Timed-up-and-Go. Balance capacity influenced the effects of the CMP manipulation on mediolateral sway amplitude (p = .023). Specifically, it positively associated with sway amplitude during the high-CMP condition (β = 0.273), but not low-CMP condition (β = -0.060). In other words, higher balance capacity was associated with increased sway during high-CMP, confirming our hypothesis that CMP does not uniformly negatively impact balance performance. Rather, CMP was maladaptive for those with better balance. Results also indicated that older adults' balance capacity influenced the degree to which they could engage conscious or automatic postural control processes. Specifically, we found that, overall, participants showed reduced mediolateral sway frequency and complexity for the high-CMP vs. low-CMP condition (p's ≤ 0.018), indicating reduced automaticity of balance (as expected). However, these effects were significantly attenuated as balance capacity reduced (i.e., smaller changes in those with lower balance capacity, p's < 0.010). Hence, the ability to readily shift between conscious and automatic modes of postural control seems more constrained as balance becomes worse. Overall, these findings suggest clinicians need to consider older adults' balance capacity when using providing instructions or feedback likely to influence CMP within rehabilitation settings.
老年人越来越依赖有意识的过程来控制平衡。虽然这可能是对与年龄相关的平衡能力下降的一种反应，但尚不清楚这种策略是否具有适应性。我们研究了平衡能力是否会改变有意识运动处理（CMP）对老年人姿势控制的影响。47名老年人（M = 74.8，范围 = 61 - 88岁）在力平台上完成了60秒的窄站姿平衡试验，试验条件旨在增加（高CMP；通过运动监测指令）或减少有意识处理（低CMP；分心任务）。平衡能力通过伯格平衡量表和计时起立行走测试的综合得分来衡量。平衡能力影响了CMP操作对左右摇摆幅度的影响（p = 0.023）。具体而言，它与高CMP条件下的摇摆幅度呈正相关（β = 0.273），但与低CMP条件下的摇摆幅度无相关性（β = -0.060）。换句话说，更高的平衡能力与高CMP期间摇摆增加有关，证实了我们的假设，即CMP并非始终对平衡表现产生负面影响。相反，CMP对平衡较好的人是适应不良的。结果还表明，老年人的平衡能力影响了他们参与有意识或自动姿势控制过程的程度。具体而言，我们发现，总体而言，与低CMP条件相比，参与者在高CMP条件下的左右摇摆频率和复杂性降低（p值≤0.018），表明平衡的自动性降低（如预期）。然而，随着平衡能力下降，这些影响显著减弱（即平衡能力较低的人变化较小，p值<0.010）。因此，随着平衡变得更差，在有意识和自动姿势控制模式之间轻松切换的能力似乎受到更多限制。总体而言，这些发现表明，临床医生在康复环境中使用可能影响CMP的指令或反馈时，需要考虑老年人的平衡能力。
