Intensive training and cardiac autonomic control in high level athletes.
OBJECTIVE
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 (VO2max) were assessed.


RESULTS
In detrained athletes, VO2max 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 VO2max 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.
Bonaduce
D
D
Institute of Internal Medicine, Cardiology and Heart Surgery, Federico II University, Naples, Italy.
Petretta
M
M
Cavallaro
V
V
Apicella
C
C
Ianniciello
A
A
Romano
M
M
Breglio
R
R
Marciano
F
F
D000293:Adolescent; D000328:Adult; D001642:Bicycling / Q000502:physiology*; D002302:Cardiac Output; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*