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1 Exercise Hemodynamic Laboratory, School of Physical Education and Sport, University of Sao Paulo, Sao Paulo, SP, Brazil; Experimental Physiopathology Division, Medical School, University of Sao Paulo, Sao Paulo, SP, Brazil
2 Exercise Hemodynamic Laboratory, School of Physical Education and Sport, University of Sao Paulo, Sao Paulo, SP, Brazil
3 Hypertension Unit, General Hospital, University of Sao Paulo, Sao Paulo, SP, Brazil
4 Unit of Cardiovascular Rehabilitation and Exercise Physiology, Heart Institute (InCor), Medical School, University of Sao Paulo, Sao Paulo, SP, Brazil
5 Endocrinology Division, General Hospital, University of Sao Paulo, Sao Paulo, SP, Brazil
* To whom correspondence should be addressed. E-mail: cforjaz{at}usp.br.
Insulin infusion causes muscle vasodilation, despite the increase in sympathetic nerve activity. In contrast, a single bout of exercise decreases sympathetic activity and increases muscle blood flow during the post-exercise period. We tested the hypothesis that muscle sympathetic activity would be lower and muscle vasodilation would be higher during hyperinsulinemia performed after a single bout of dynamic exercise. Twenty-one healthy young men randomly underwent two hyperinsulinemic euglycemic clamps performed after 45 min of seated rest (Control) or bicycle exercise (50% of VO2peak). Muscle sympathetic nerve activity (MSNA, microneurography), forearm blood flow (FBF, plethysmography), blood pressure (BP, oscillometric method), and heart rate (HR, ECG) were measured at baseline (90 min after exercise or seated rest) and during hyperinsulinemic euglycemic clamps. Baseline glucose and insulin concentrations were similar in the exercise and control sessions. Insulin sensitivity was unchanged by previous exercise. During the clamp, insulin levels increased similarly in both sessions. As expected, insulin infusion increased MSNA, FBF, BP and HR in both sessions (23±1 vs. 36±2 burst/min, 1.8±0.1 vs. 2.2±0.2 ml.min-1per100ml-1, 89±2 vs. 92±2 mmHg, and 58±1 vs. 62±1 beat/min, respectively, p<0.05). BP and HR were similar between sessions. However, MSNA was significantly lower (27±2 vs. 31±2 burst/min), and FBF was significantly higher (2.2±0.2 vs. 1.8±0.1 ml.min-1per100ml-1, P<0.05) in the exercise session when compared with the control session. In conclusion, in healthy men, a prolonged bout of dynamic exercise decreases MSNA and increases FBF. These effects persist during acute hyperinsulinemia performed after exercise.
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