Novel nonlinear method of heart rate variability analysis in exercise

Global chaotic analysis of heart rate variability (HRV) has been previously investigated. Preceding studies indicated impaired analysis in obese children and diabetic patients. However, its behaviour in response to exercise is not clear. We investigated the acute effects of physical exercise on global chaotic analysis of HRV. We investigated 35 healthy men aged between 18 and 35 years old. Volunteers were instructed not to drink alcohol, caffeine or other autonomic nervous system (ANS) stimulants for 24 hours before the evaluation. Volunteers performed physical exercise on treadmill with intensity of 6.0 km/hour + 1% slope in the first five minutes for physically "warming up". This was then followed by 25 minutes with intensity equivalent to 60% of V-max, with the same slope according to the Conconi threshold. HRV was analyzed in the following periods: (a) control protocol; the 10-minute periods before the performance of the exercise and (b) the 10-minute periods after the performance of the exercise. Both periods of exercise were analyzed by the chaotic global techniques. The number of RR-intervals derived from the PQRST-motif of the ECG signal was processed by the algorithms, and were always 750 RR-intervals for all subjects both experimental and control.