Effect of long term physical training on heart rate variability

The purpose of this study was to investigate the influence of physical training on the autonomic nervous system in healthy subjects. The authors compared 28 trained athletes and 28 sedentary subjects and divided them into two age groups: 18 to 34 and 35 to 55 years of age. ECG was recorded during 2 minutes while the subjects were breathing periodically under metronome control. RR tachograms were obtained and heart rate variability (HRV) was calculated. In the younger subgroup (18-34 years of age) only the standard deviation of mean RR interval and the frequency content were significantly different. In the older subgroup (35-55 years of age), all measured parameters were significantly different. A clear peak around 0.083 Hz, in coherence with respiratory rate, was observed in athletes and was present to a much smaller amplitude in sedentary subjects. These results show that regular physical training enhances the synchronization between heart rate and respiratory frequency, with a more pronounced effect at a higher age. The fact that physical training has a distinct impact on HRV in healthy subjects, infers that exercising may be of value in the modification of cardiac autonomic activity in cardiac patients.