Abstract des Autors

Frequency domain analysis of heart rate variability (HRV) may potentially identify the dominance exhibited by different branches of the autonomic nervous system. Autonomic contribution to cardio-deceleration following exercise has been studied in adults; however, no data are available for endurance trained juvenile athletes. The aim of this study was to evaluate the association between the increase in heart rate following exercise and any change in HRV frequency components in trained juveniles.
A 6 min resting ECG (lead 2) was recorded from trained juvenile cyclists (23 male, 7 female, mean age 14.7 years), before (Pre) and after (Post) incremental exercise to volitional exhaustion on a stationary cycle ergometer. Each subject performed a progressive ramp protocol where power increased by 20W min-1, with initial power set at 60 W for females and 100 W for males. Oxygen uptake (¦O2) was measured using breath-by-breath techniques. ECG was analysed in both time and frequency domains using commercially available software. Mean ¦O2max was 75.5 ml Kg-1 min-1, and mean power at ¦O2max was 440 W. The R-R interval SD was lower following exercise (Pre: 86ms vs. Post: 36ms, P<0.01). Normalised high frequency HRV was lower (Pre: 36.5 vs. Post: 18.7, P<0.01) and normalised low frequency HRV was higher (Pre: 58.5 vs. Post: 75.0, P<0.01) following exercise. In elite juvenile athletes there were no associations between exercise-induced changes in high frequency variability and heart rate (R2=0.073). This suggests that in elite juveniles, the heart may be less sensitive to vagal influences - a suggestion further supported by the relatively high pre-exercise resting heart rates with normal high frequency variability. Verf.-Referat