EFFECT OF AEROBIC TRAINING ON BAROREFLEX REGULATION OF CARDIAC AND SYMPATHETIC FUNCTION

To investigate the effect of aerobic exercise training on baroreflex r egulation of muscle sympathetic nerve activity (MSNA) and cardiac R-R intervals in a middle-aged to older population, 10 healthy men >40 yr of age underwent tests of autonomic function before and after 12 wk of high-intensity training. Cardiac and peripheral baroslopes were deter mined from the R-R interval vs. mean arterial pressure (MAP) and peron eal MSNA vs, diastolic pressure relationships, respectively, during se quential bolus injections of nitroprusside and phenylephrine. Maximal oxygen uptake increased (P < 0.05) 17% with training. Resting R-R inte rval increased (881 +/- 23 to 956 +/- 38 ms, P < 0.05), MAP decreased (96 +/- 2 to 91 +/- 3 mmHg, P < 0.05), and MSNA was unaltered (23.1 +/ - 2.3 to 23.6 +/- 1.9 bursts/min) with training. Before and after trai ning, respectively, cardiac baroslopes determined with decreasing (8.7 +/- 0.9 to 9.9 +/- 5.5 ms/mmHg) and increasing MAP (9.6 +/- 2.1 to 9. 9 +/- 2.2 ms/mmHg) and the peripheral sympathetic baroslope (-3.3 +/- 0.4 to -3.5 +/- 0.6 bursts min(-1).mmHg(-1)) did not differ. The resul ts suggest that shortterm aerobic training does not alter resting MSNA or neurocirculatory responses to baroreceptor challenges in middle-ag ed and older men.