Power spectral analysis of RR interval and blood pressure short-term variability at rest and during dynamic exercise: comparison between cyclists and controls.

To determine the adaptations of the autonomic nervous system in the control of heart rate and blood pressure induced by endurance training, 10 competitive cyclists aged 27 +/- 7 years and 10 age-, weight- and height-matched sedentary controls were subjected to Power Spectral Analysis of the RR interval and of blood pressure at supine rest and during submaximal cycloergometric exercise test in the supine position at 20% and 40% of maximal workload. At rest, the high-frequency (HF) power of the RR interval was higher in cyclists (p < 0.05) compared to controls, whereas the power spectrum of both systolic and diastolic blood pressure did not differ between cyclists and controls. During exercise the variance, the low-frequency (LF) and the HF power of the RR interval decreased significantly (p < 0.005) and similarly in cyclists and controls. The LF/HF ratio of the RR interval increased (p < 0.001) and the alfa index of baroreflex sensitivity decreased (p < 0.05) without differences between cyclists and controls. The variance of both systolic and diastolic blood pressure increased (p < 0.001 and p < 0.005, respectively) as well as the HF power of systolic blood pressure (p < 0.001) similarly in cyclists and in controls. In conclusion, the data of the present study suggest that competitive cycling causes an enhanced vagal drive to the sinus node, whereas the neural control of blood pressure is not affected. During exercise a vagal withdrawal and a sympathetic activation in the neural control of heart rate, together with a reduction of baroreflex sensitivity are operative. These changes are similar in cyclists and controls.