Short-term heart rate variability changes after exercise training in subjects following myocardial infarction.

Heart rate variability reflects the activity of autonomic nervous system. The aim was to evaluate the value of short-term spectral analysis of heart rate for monitoring the effects of exercise training on the autonomic nervous system in subjects following myocardial infarction. Short-term spectral analysis of heart rate variability was performed during standardised supine-standing-supine test in a group of 29 clinically stable patients after myocardial infarction and the same test was repeated after 2 months of exercise training (ergometry or rapid walking). Each subject exercised at 60-80% of his maximal performance for 30 minutes once a day. Short-term spectral analysis of heart rate variability was assessed in the frequency range of 0.02-0.5 Hz involving very low frequency (VLF, 0.02-0.05 Hz), low frequency (LF, 0.05-0.15 Hz) and high frequency (HF, 0.15-0.5 Hz) spectral bands. The influence of exercise training on the autonomic nervous system was registered in the physically active group (n = 16) as a decrease in sympathetic response to standardised orthostatic load. In conclusions the regular exercise influenced an altered neural autonomic regulation of heart rate in post-infarction patients shown by a decrease in sympathetic activity in the short-term heart rate variability. This method enables monitoring of the effects of physical training on the autonomic nervous system in patients following myocardial infarction.