Muscle sympathetic nerve activity during isometric exercise in patients with cerebrovascular accidents.

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Although isometric exercise is useful for improvement of muscle strength in unaffected limbs of patients with cerebrovascular accidents (CVA), the pressor responses induced by cardiovascular changes during static exercise in CVA patients are not well defined. We compared the cardiovascular responses to static exercise of elbow flexor muscle between 8 patients with 3-month history of CVA who had documented damage of subcortical structures and 8 control men. Changes in heart rate (HR), arterial blood pressure (BP) and muscle sympathetic nerve activity (MSNA), recorded from the peroneal nerve on the affected side, were determined before, during and after a 2-min sustained contraction of elbow flexor muscles at 35% maximal voluntary contraction. During the control period, the mean burst count of MSNA in CVA patients (64.5±5.0 beats/100HR) was higher than in control subjects (43.5±7.1 beats/100HR) (P<K 0.05). Total MSNA (the mean burst amplitude per minute times burst rate) increased significantly in CVA and control during static exercise by 18.7±6.3% and 95.8±25.2%, respectively. The percent changes in total MSNA, HR and MBP in CVA patients were attenuated during static exercise, compared with the control subjects. Our results indicated the presence of intact pressor responses during static exercise in CVA patients although the magnitudes of such responses were attenuated relative to the control. Therefore, damage of subcortical structures might be involved in lowering the pressor response during exercise. Our results indicate that static exercise does not put patients with CVA at risk of marked increases in HR and BP.