Medicine & Science in Sports & Exercise^®

Volume 30, Number 5

May 1998

Abstracts

Clinical Investigations

Intensive training and cardiac autonomic control in high level athletes

DOMENICO BONADUCE, MARIO PETRETTA, VINCENZO CAVALLARO, CLAUDIO APICELLA, ANGIOLINO IANNICIELLO, MASSIMO ROMANO, ROBERTO BREGLIO, and FORTUNATO MARCIANO

Institute of Internal Medicine, Cardiology and Heart Surgery, "Federico II" University, Naples, ITALY; and Institute of Cybernetics, National Research Council (CNR), Naples, ITALY

BONADUCE, D., M. PETRETTA, V. CAVALLARO, C. APICELLA, A. IANNICIELLO, M. ROMANO, R. BREGLIO, and F. MARCIANO. Intensive training and cardiac autonomic control in high level athletes. Med. Sci. Sports Exerc., Vol. 30, No. 5, pp. 691-696, 1998. Purpose: We aimed to evaluate in a longitudinal study the effect of intensive training on cardiac autonomic control in athletes using 24-h heart rate variability analysis. Methods: Time and frequency domain measures of heart rate variability were calculated from 24-h Holter monitoring in 15 high level bicyclists (mean age 21 ± 4 yr) after 1 month of detraining and after 5 months of vigorous training. At the same times echocardiographic left ventricular mass and dimensions and maximal oxygen consumption (V(dot)O_2max) were assessed. Results: In detrained athletes, V(dot)O_2max values, left ventricular mass and dimensions, and time and frequency domain measures of vagal modulation of heart rate were higher than in a group of untrained subjects of similar age while heart rate and the low-to-high frequency ratio were lower, indicating an enhanced vagal modulation of heart rate in athletes as compared with that in control subjects. After 5 months of vigorous training, left ventricular mass and dimensions and V(dot)O_2max increased in athletes, while heart rate decreased further. In contrast, no changes were detectable in time and frequency domain measures of heart rate variability over the entire 24-h and in both waking and sleeping hours. Conclusions: This study demonstrates that an increased cardiac vagal control is detectable in detrained athletes; however, after intensive training, despite a significant decrease in heart rate, time and frequency domain measures of heart rate variability reflecting cardiac vagal control remain unchanged. Thus, other mechanisms than changes in cardiac autonomic control could be involved in determining the profound bradycardia of athletes. Key Words: SYMPATHO-VAGAL BALANCE, DYNAMIC EXERCISE, HEART RATE VARIABILITY

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