Effect of Dual-task Standing on prefrontal-motor Cortex Activation and postural-related Muscle Activity between Young and Older Adults.

The purpose of this study was to investigate the effects of dual-task standing on postural-related muscle activity and cortical activation in both young and older groups. Fourteen older adults and thirteen young adults were recruited. Participants performed single-task and dual-task standing. The surface electromyographic signals of tibialis anterior, solus, rectus femoris, and biceps femoris at left and right sides were recorded. Simultaneously, cortical activation in the dorsolateral prefrontal and motor cortices were measured. Two-way MANOVAs with repeated measures and Pearson correlation analyses were employed for the statistical analysis. Our results indicated that only the older group presented greater right (p = .002) and left (p = .003) ankle muscle co-activation index, and greater cortical activation in the dorsolateral prefrontal cortex (p < .001), premotor motor cortex (p = .011), supplementary motor area (p = .043), and primary motor cortex (p = .028) in the left hemisphere during dual-task compared to single-task standing. Additionally, the older group showed negative correlations, whereas the young group showed positive correlations between cortical activation and average linear envelope of muscle activity during the single-task standing. Furthermore, the older group showed more significant positive correlations between cortical activation and average linear envelope of muscle activity than the young group during dual-task standing. These observations suggest that age-related overactivation of the prefrontal-motor cortex may lead to redundant ankle joint muscle response during dual-task standing.