Shumway-Cook A, Woollacott M, Kerns K A, Baldwin M
Department of Physical Therapy, Northwest Hospital, Seattle, USA.
J Gerontol A Biol Sci Med Sci. 1997 Jul;52(4):M232-40. doi: 10.1093/gerona/52a.4.m232.
This study used a dual task design to investigate the effects of two different types of cognitive tasks on stability (as measured by center of pressure displacement) in young vs older adults with and without a history of falls.
Two secondary cognitive tasks, a sentence completion and a visual perceptual matching task, were used to produce changes in attention during quiet stance under flat vs compliant surface conditions in 20 healthy young adults, 20 healthy older adults, and 20 older adults with a history of imbalance and falls. Postural stability was quantified using forceplate measures of center of pressure (COP). Speed and accuracy of verbal response on the cognitive tasks were also quantified.
During the simultaneous performance of a cognitive and postural task, decrements in performance were found in the postural stability measures rather than the cognitive measures for all three groups. While no differences were found between the young adults and the older healthy adults on the firm surface, no task condition, when task complexity was increased (either through the introduction of a secondary cognitive task, or a more challenging postural condition such as standing on the compliant surface), significant differences in postural stability between the two groups became apparent. In contrast to the young and healthy older adults, postural stability in older adults with a history of falls was significantly affected by both cognitive tasks.
Results suggest that when postural stability is impaired, even relatively simple cognitive tasks can further impact balance. Results further suggest that the allocation of attention during the performance of concurrent tasks is complex; depending on many factors including the nature of both the cognitive and postural task, the goal of the subject and the instructions.
本研究采用双任务设计，以调查两种不同类型的认知任务对有或无跌倒史的年轻人和老年人稳定性（通过压力中心位移测量）的影响。
在平坦和顺应性表面条件下的安静站立过程中，使用两个次级认知任务，即句子完成任务和视觉感知匹配任务，来改变20名健康年轻人、20名健康老年人以及20名有失衡和跌倒史的老年人的注意力。使用压力板测量压力中心（COP）来量化姿势稳定性。还对认知任务中言语反应的速度和准确性进行了量化。
在认知任务和姿势任务同时进行期间，发现所有三组的姿势稳定性测量指标出现了表现下降，而非认知测量指标。在坚硬表面上，年轻人和健康老年人之间未发现差异，但当任务复杂性增加时（无论是通过引入次级认知任务，还是更具挑战性的姿势条件，如站在顺应性表面上），两组之间姿势稳定性的显著差异变得明显。与年轻人和健康老年人不同，有跌倒史的老年人的姿势稳定性受到这两种认知任务的显著影响。
结果表明，当姿势稳定性受损时，即使是相对简单的认知任务也会进一步影响平衡。结果还表明，在同时执行任务期间注意力的分配很复杂；这取决于许多因素，包括认知任务和姿势任务的性质、受试者的目标以及指令。
