EFFECT OF ATHLETIC TRAINING ON HEART-RATE-VARIABILITY

The time and frequency domain components of heart rate variability hav e been used to assess prognosis in patients with different types of he art disease. However, the effect of habitual exercise, which influence s baseline parasympathetic tone, on heart rate variability has not bee n fully evaluated. To determine the effect of chronic exercise on hear t rate variability, we studied 12 athletes and 18 control subjects. Ti me domain and frequency domain analysis was performed on 15-minute res ting heart rate acquisitions. Athletes had evidence of increased vagal activity in the time domain compared with control subjects (eg, incre ased standard deviation of R-R intervals) but showed evidence of decre ased power in variables reflecting vagal activity in the frequency dom ain (eg, total power and high-frequency power). Of note, there was goo d correlation between time and frequency domain variables, which refle cted parasympathetic tone in the control group that was not seen in at hletes. These data suggest that frequency domain analysis of heart rat e variability may not be an accurate indicator of cardiac vagal tone i n chronically trained endurance athletes and activity level may have t o be considered when using heart rate variability to carry out prognos tic stratification in patients with heart disease.