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a Department of Exercise and Movement Science and Institute of Neuroscience, University of Oregon, Eugene, Oregon
b Division of Physical Therapy, Department of Rehabilitation Medicine, University of Washington Medical School, Seattle, Washington.
Marjorie H. Woollacott, University of Oregon, Department of Exercise and Movement Science, Eugene, Oregon 97403-1240 E-mail: mwool{at}oregon.uoregon.edu.
Decision Editor: William B. Ershler, MD
Background. Previous literature indicates that attentional resources are required for recovery of postural stability. Previous studies have also examined the effect of aging on the performance of a static postural task while a secondary cognitive task is being conducted. This study describes the effect of a cognitive task on the neuromuscular response characteristics underlying reactive balance control in young versus older adults.
Methods. The attentional demand on the neuromuscular system was examined in 14 young and 12 healthy older adults by analysis of the integrated electromyography activity while the adults were performing a dual-task paradigm. The primary task involved standing platform perturbations and the secondary task was a math task that involved subtraction by threes. Integrated electromyography activity was compared between the cognitive (math and balance) task versus control (balance only) task.
Results. For both groups of subjects, onset latency of postural muscle responses did not change under dual-task conditions. In contrast, the amplitude of postural muscle activity was significantly affected by performance of a secondary task. When electromyography data were combined for both young and older adults, there was a decrease in muscle response amplitude in both agonist (gastrocnemius) and antagonist (tibialis anterior) muscles when the cognitive math task was performed. This was apparent at 350–500 milliseconds from plate onset for the gastrocnemius and between 150 and 500 for the tibialis anterior. When young and older adults were compared, an age by task interaction effect was seen in muscle response amplitude for the agonist (gastrocnemius) muscle between 350 to 500 milliseconds, with older adults showing a significantly greater reduction than young adults.
Conclusion. The decline of muscle activity when the secondary task was performed suggests that less attentional processing capacity was available for balance control during the dual-task paradigm. The results also indicate that the dual-task activity has a greater impact on balance control in the older adults than in the young adults.
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 M. S. Redfern, M. L.T.M. Muller, J. R. Jennings, and J. M. Furman Attentional Dynamics in Postural Control During Perturbations in Young and Older Adults J. Gerontol. A Biol. Sci. Med. Sci., August 1, 2002; 57(8): B298 - 303. [Abstract] [Full Text] [PDF]
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S. G. Brauer, M. Woollacott, and A. Shumway-Cook The Interacting Effects of Cognitive Demand and Recovery of Postural Stability in Balance-Impaired Elderly Persons J. Gerontol. A Biol. Sci. Med. Sci., August 1, 2001; 56(8): M489 - 496. [Abstract] [Full Text] [PDF]
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| Journals of Gerontology Series B: Psychological Sciences and Social Sciences | |
