Effect of year-round training on parameters of heart rate variability, central hemodynamics and physical working capacity in short-distance swimmers

Abstract

Dynamic examination of athletes is of great interest for sports medicine specialists, as it allows measuring changes in athletes’ functional state in parallel with increasing athletic performance in a one-year training cycle. The aim of the work is to assess dynamic changes in parameters of heart rate variability, central hemodynamics and physical performance in short-distance swimmers during preparatory and competitive periods of the training process. Materials and methods. The swimmers (n = 94) qualified from the second-class sport qualification to Master of Sports of International Class were examined during the preparatory and competitive periods of the training process. Short ECG recordings of 5 minutes were used for the heart rate variability (HRV) analysis according to the International Standard. Results. In the preparatory period, the autonomic equilibrium index had a mean value of 3.104 ± 0.494 1/s2, and in the competitive period – 2.459 ± 0.248 1/s2 (P = 0.295). The initial distribution of athletes depending on the value of autonomic tone, according to the classification proposed by R. M. Bayevskiy, had the following ratio in the preparatory period: 75.0 % / 20.0 % / 5.0 %, vagotonic, normotonic and sympathotonic individuals, respectively, statistically significantly indicating the prevalence of athletes with vagotonia over normotonic individuals (P = 0.0005). In the competitive period, this ratio was 60.0 % / 40.0 % / 0 %. The central hemodynamic indices showed a downward trend as evidenced by a decrease in the cardiac index from 2.954 ± 0.126·l·min-1·m-2 to 2.862 ± 0.088 l‧min-1‧m-2 (Р = 0.510), although these values matched to the eukinetic circulatory type (CT) during both training periods. However, the ratio of hypokinetic, eukinetic and hyperkinetic CT in the preparatory period was 45.0 % / 45.0 % / 10 0 %, and in competitive period – 45.0 % / 55.0 % / 0 %, respectively. The mean value of physical working capacity (PWC170/kg) in the preparatory period was 15.54 ± 0.66 kgm·min-1·kg-1, and in the competitive period it was 18.09 ± 0.53 kgm·min-1·kg-1, making an increase of 16.41 % (Р = 0.0001). The functional state index (FSI) increased significantly by 25.08 % from 5.558 ± 0.322 r. u. to 6.952 ± 0.272 r. u. (Р = 0.00001). The correlation analysis during the preparatory period showed a significant positive correlation between Mo and PWC170/kg (r = 0.46, P = 0.040), ARI and CI (r = 0.50, P = 0.026), IARP and CI (r = 0.53, P = 0.017), stress-index and SI (r = 0.52, P = 0.019) and negative – between Mo and CI (r = -0.56, P = 0.009). In the competitive period, the general tendency of correlation interaction was remained, as evidenced by revealed positive relationships between Mo and FSI (r = 0.53, P = 0.017), ARI and SI (r = 0.51, P = 0.020). Conclusions. Short-distance swimmers in the competitive period had significantly higher level of physical working capacity (by 16.4 %), the functional state index (by 25.1 %), as well as parasympathetic tone of ANS in comparison with the preparatory period. The above-mentioned hemodynamic changes and autonomic balance indicators were associated with the increase in athletic performance: 4 (20 %) swimmers qualified for the title of Master of Sports of Ukraine, 2 (10 %) swimmers – for Candidate Master of Sports, and 2 (10 %) swimmers – for first-class sport qualification.