Controlled 5-mo aerobic training improves heart rate but not heart rate variability or baroreflex sensitivity

Endurance-trained athletes have increased heart rate variability (HRV), but it is not known whether exercise training improves the HRV and baroreflex sensitivity (BRS) in sedentary persons. We compared the effects of low- and high-intensity endurance training on resting heart rate, HRV, and BRS. The maximal oxygen uptake and endurance time increased significantly in the hi gh-intensity group compared with the control group. Heart rate did not chan ge significantly in the low-intensity group but decreased significantly in the high-intensity group (-6 beats/min, 95% confidence interval; -10 to -1 beats/min, exercise vs. control). No significant changes occurred in either the time or frequency domain measures of HRV or BRS in either of the exerc ise groups. Exercise training was not able to modify the cardiac vagal outf low in sedentary, middle-aged persons.