Abstract 543: Exercise Training Restores Muscle Metaboreflex Control of Sympathetic Nerve Activity in Never-Treated Hypertensive Patients
Introduction: We have recently reported that muscle metaboreflex control of muscle sympathetic nerve activity (MSNA) is impaired in hypertensive patients.
Hypothesis: We tested the hypothesis that exercise training would improve muscle metaboreflex control of MSNA in hypertensive patients.
Methods: Twenty never-treated hypertensive patients were randomly divided into 2 groups: exercise-trained (n=11; age 46±2 years) and untrained (n=9; age 42±2 years). An age-matched normotensive exercise-trained group (n=12; age 42±2 years) was also studied. MSNA (microneurography), forearm blood flow (plethysmography) and blood pressure (BP, oscillometric) were evaluated at rest, during handgrip exercise at 30% maximal voluntary contraction, and during post-handgrip circulatory arrest. Exercise training consisted of a four-month period, 3 times/wk, at anaerobic threshold to 70% VO2peak
Results: Baseline mean BP levels were significantly higher in hypertensive patients when compared with normotensive individuals (110±1 vs. 91±2 mmHg, P<0.001). Similarly, MSNA levels were significantly higher in hypertensive patients (35±1 vs. 22±1 bursts/min, P<0.001). Forearm vascular conductance (FVC) was significantly lower in hypertensive patients when compared with normotensive individuals (2.12±0.22 vs. 3.38±0.35 units, P<0.001). Exercise training significantly reduced BP and MSNA levels at rest and during handgrip exercise in hypertensive patients. Exercise significantly increased FVC at rest and during handgrip exercise in hypertensive patients. During post-handgrip circulatory arrest, when muscle metaboreflex is isolated, exercise training significantly increased MSNA levels in hypertensive patients (2±1 vs. 10±2 bursts/min, P=0.02). In addition, the baseline differences in muscle metaboreflex control of MSNA between hypertensive patients and normotensive individuals were no longer observed (10±2 vs. 10±2 bursts/min, P=0.99, respectively). No significant changes were found in untrained hypertensive patients.
Conclusions: Exercise training improves neurovascular control during moderate handgrip exercise in hypertensive patients. Exercise training restores muscle metaboreflex control of MSNA in these patients.