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.