Sex-related differences in heart rate variability in cross-country skiers

Background: Heart rate variability in athletes exhibits sex-related differences. Aim: The work aimed to study sex-related characteristics of heart rate variability in cross-country skiers. Methods: During the general preparatory training period, 289 male and 113 female athletes aged 18–32 years from the Republic of Komi national cross-country skiing teams with sports qualification of at least first category were assessed. A 5-minute electrocardiogram (ECG) recording was obtained in the supine position, and heart rate variability was analyzed using the Ecosan-2007 hardware-software system (Medical Computer Systems, Russia). Statistical significance of intergroup differences was evaluated using the Mann–Whitney U test. Results: Significant differences in several heart rate variability parameters were found in athletes of both sexes. Compared with women, men exhibited higher values of mode (Mo) (p 0.001), mean RR interval (p 0.001), maximum (Max) (p 0.001) and minimum (Min) (p 0.001) RR intervals, and the relative (%) power of the high-frequency spectrum (p=0.023). Women showed higher heart rate (p 0.001), the Max/Min RR ratio (MxRMn) (p=0.02), low-frequency to high-frequency ratio (p=0.038), and index of centralization (p=0.022). Conclusion: Cross-country skiers demonstrate sex-specific features of autonomic heart rate regulation. Compared with female athletes, male exhibit a more economical mechanism of autonomic regulation of heart rhythm and a more pronounced shift in autonomic balance toward the parasympathetic nervous system.