Comprehensive rhythmocardiographic assessment of functional status in elite athletes specializing in skiing disciplines

Abstract

Problem statement: In endurance sports, rapid and valid evaluation of functional readiness is essential for balancing performance enhancement with the prevention of maladaptation. Cross-country skiing imposes high demands on the cardiovascular and autonomic regulatory systems, yet routine monitoring in practice still relies predominantly on conventional heart-rate responses and does not fully exploit the diagnostic value of heart rhythm structure. Approach: The present study applied a comprehensive rhythmocardiographic strategy that integrated variational pulsometry, spectral heart rate variability analysis, and structural-linguistic interpretation of the heart rhythm wave pattern. Purpose: To determine the characteristics of cardiovascular regulation and the overall functional state of qualified cross-country skiers at rest and after intensive exercise. Material and methods: Twenty-six qualified athletes aged 18-32 years underwent a standardized examination including 5-min rhythmocardiographic recordings in the supine position before exercise and at the 10th minute after intensive muscular work. The protocol included time-domain and spectral heart rate variability indices, Baevsky-derived regulatory indices, structural-linguistic assessment of spectrum configuration, ergometry, heart-rate monitoring, and non-parametric statistical analysis. Results: The post-exercise state was characterized by a marked increase in heart rate, shortening of RR intervals, reduction of overall variability, and a substantial rise in Baevsky's stress index, indicating stronger sympathetic activation and centralization of regulation. Spectral analysis demonstrated significant increases in the very-low-frequency, low-frequency, and especially very-high-frequency components, while structural-linguistic analysis showed a higher total number of spectral lines and a greater contribution of unstable spectral patterns after exercise. Based on the integrated response profile, three functional groups were identified: athletes with an adequate adaptive response (n = 13; 50.0%), athletes with pronounced regulatory strain (n = 7; 26.9%), and athletes with unstable functional states associated with an unfavorable adaptation prognosis (n = 6; 23.1%). Conclusions: The combined rhythmocardiographic approach provides a more informative assessment of autonomic balance, regulatory strain, and adaptive stability than isolated indices alone. It can be used for individualized monitoring of training readiness, early detection of maladaptive responses, and short-term prediction of tolerance to intensive training and competitive loads in elite crosscountry skiers.