Assessment of sport-related psychophysical stress during athletics training and competition

Heart rate variability (HRV) is the time interval variation between two consecutive R-wave peaks (RR) in the electrocardiogram (ECG). Historically, HRV was used to assess the cardiac performing time and frequency domain analysis over a RR series longer than 125s. In case of athletes, during workout or competition, ECGs tracks are usually shorter than 125s when acquired with portable sensors. On athletes, the HRV analysis is employed to estimate athletes’ psychophysical conditions. In case of short ECG tracks, the symbolic analysis has been proposed to assess cardiac autonomic control in literature. Thus, the aim of the thesis is to assess sport-related psychophysical stress during athletics training and competition, applying symbolic analysis on RR series. Data are a collection of 200 ECGs acquired on 10 young subjects practicing athletics running, during two different workouts (strength and speed) and competition. In these three conditions, six common phases can be distinguished: pre-warm-up, post warm-up, post exercise 5 minutes, 10 minutes, and 15 minutes of rest after exercise. Data were pre-processed and analysed in Matlab® environment. RR series were extracted from each ECG and the symbolic analysis was applied on each tachogram. The results of symbolic analysis were compared through nonparametric rank sum test. The main results show no significant differences between speed training and competition, suggesting that similar sporting gestures do not provide differences in sympathetic or parasympathetic activity. Moreover, V0 is major in speed training and competition than in strength training indicating a greater sympathetic control during an aerobic activity than anaerobic one. The values of RRmean parameters confirms a high sympathetic activity in competition and speed workout than in strength training. The UV2 incidence is higher in strength training than in other condition. Finally, about 93% of the matches reporting statistical differences, are located in the phases following physical effort and report a level of sympathetic activity higher in competition than in training. A psychological component, linked to the great importance that subject gives to the race, creates sensations antagonist to the subsequent "relaxation", which normally occurs after physical activity leading to an abnormal activity of sympathetic system. The study suggests that symbolic analysis is an excellent tool for evaluating the cardiac autonomic control, while subjects are practicing sports. Symbolic analysis of the tachogram provides information about psychophysical athlete state and could be used as a complementary tool to stress assessment tests. Symbolic analysis has widespread application in many sectors, as in the economic and financial fields and, in the last 20 years, its use in the medical research field has increased a lot.