The role of lower leg muscle activity in blood pressure maintenance of older adults
Age-associated muscle weakness, postural instability, and orthostatic hypotension have been identified as contributing factors to falls, but the relationships among them are not clear. Therefore, the purpose of this study, a two-way factorial design, was to investigate the differences in lower extremity (LE) muscle activity, blood pressure (BP), and heart rate (HR) between young and older individuals in an upright position. Methods. Ten young males (20-24 yrs.) and 10 older males (65-82 yrs.) stood for 15 minutes while BP, HR, and LE electromyography (EMG) were recorded at one minute intervals. A two-way ANOVA was used for data analysis, p≤.05. Results. Mean arterial pressure of both groups significantly increased from supine values within one minute of standing (young = 86.5±1.68 to 96.9±3.16 mmHg, old = 100.3±4.42 to 114.0±5.40 mmHg). BP variables remained elevated during the 15 minutes of standing despite a significantly attenuated HR response in the older group (young = 85±4.51 bpm, old = 73±3.98 bpm). Standing EMG activity of the older group was significantly greater than the young group. Conclusion. This study suggests that increased LE muscle activity may play a role in the ability of older individuals to maintain BP in the standing position.