Brauer S G, Woollacott M, Shumway-Cook A
Department of Exercise and Movement Science, University of Oregon, Eugene, OR, USA.
J Gerontol A Biol Sci Med Sci. 2001 Aug;56(8):M489-96. doi: 10.1093/gerona/56.8.m489.
Although postural recovery is attentionally demanding in healthy elderly persons, an inability to recover balance due to competition for attentional resources between the postural system and a second task could contribute to falls in older adults with poor balance. This study examined the attentional demands of balance recovery from a mild postural disturbance in balance-impaired elderly persons. A second purpose of this research was to determine the effect of performing a cognitive task on the recovery of balance in balance-impaired elderly persons.
Fifteen healthy older adults and 13 older adults with clinical balance impairment were exposed to balance disturbances by means of sudden movement of a platform on which they stood. A dual-task paradigm where postural recovery served as the primary task and verbal reaction time to auditory tones served as the secondary task was used to assess attentional demand. To determine the effect of the cognitive task on postural recovery, kinetic, kinematic, and neuromuscular measures of a feet-in-place response were investigated.
Balance recovery using a feet-in-place response was attentionally demanding in both groups of older adults and was more demanding in balance-impaired than in healthy elderly persons. With the concurrent performance of a cognitive task, balance-impaired elderly persons took longer to stabilize their center of pressure and regain balance than in a single task, while healthy elderly persons showed no change between conditions. In addition, only balance-impaired elderly individuals had a greater center-of-pressure resultant velocity during recovery in a dual-task compared with a single-task situation.
The ability to recover balance using a feet-in-place response was more attentionally demanding in balance-impaired than in healthy elderly persons. The recovery of balance was also slower and less efficient in balance-impaired elderly persons when simultaneously performing a cognitive task, whereas the ability of healthy elderly individuals to recover was not influenced by concurrent task demands. This suggests that dual-task performance may contribute to postural instability and falls in balance-impaired elderly individuals.
尽管姿势恢复对健康老年人来说需要集中注意力，但由于姿势系统和第二项任务之间争夺注意力资源而导致无法恢复平衡，可能会导致平衡能力差的老年人跌倒。本研究考察了平衡能力受损的老年人从轻度姿势干扰中恢复平衡时的注意力需求。本研究的另一个目的是确定执行认知任务对平衡能力受损的老年人平衡恢复的影响。
15名健康老年人和13名有临床平衡障碍的老年人通过站立平台的突然移动来暴露于姿势干扰中。采用双任务范式，其中姿势恢复作为主要任务，对听觉音调的言语反应时间作为次要任务，以评估注意力需求。为了确定认知任务对姿势恢复的影响，研究了原地双脚反应的动力学、运动学和神经肌肉指标。
两组老年人使用原地双脚反应进行平衡恢复都需要集中注意力，且平衡能力受损的老年人比健康老年人更需要注意力。在同时执行认知任务时，平衡能力受损的老年人比单任务时需要更长时间来稳定其压力中心并恢复平衡，而健康老年人在不同条件下没有变化。此外，与单任务情况相比，只有平衡能力受损的老年人在双任务恢复过程中的压力中心合成速度更大。
与健康老年人相比，平衡能力受损的老年人使用原地双脚反应恢复平衡的能力需要更多的注意力。当同时执行认知任务时，平衡能力受损的老年人平衡恢复也更慢且效率更低，而健康老年人的恢复能力不受同时进行的任务需求的影响。这表明双任务表现可能导致平衡能力受损的老年人姿势不稳定和跌倒。
