Mid Sweden University

Background Most sex comparisons in endurance sports have been derived from performance-matched groups of female and male athletes competing over similar distances within summer sports. Corresponding analyses of sex differences in winter endurance sports have not previously been conducted. In the Olympic Winter Games (OWG), the endurance sports include cross-country skiing (XCS), biathlon (BIA), Nordic combined (NC), ski mountaineering (SkiMo) and long-track speed skating (SpSk). The aim of this narrative review is to provide a comprehensive analysis of the sex differences in performance and performance-determining factors in the OWG endurance sports. Main Body Sex differences in competition speeds are similar to 7-16% in XCS, 12-16% in BIA and 7-11% in SpSk, with race distances often shorter for women compared to men. No comparable data have been published for NC or SkiMo. Slower skiing speeds among women are associated with greater use of the diagonal and gear 2 sub-techniques in classic and skate skiing, respectively. In SpSk, slower skating speeds among women may be related to a less effective push-off being maintained throughout races. Laboratory data have revealed absolute and relative peak aerobic capacity to be 30-63% and 10-27% greater, respectively, in male versus female XCS, BIA, NC, SkiMo and SpSk athletes. There is limited evidence of sex differences in training characteristics, although women currently tend to complete more strength training than men in XCS and BIA. Of note, most data have been derived from studies performed in XCS, with almost no studies investigating sex differences in NC or SkiMo. Conclusions This review provides a comprehensive overview of sex differences in performance and performance-determining factors within and between OWG endurance sports, which provides a scientific basis for designing training programs and future studies. Due to the lack of research investigating sex differences in NC and SkiMo, these sports, in particular, would be worthy of further attention. Key Points center dot This narrative review provides a novel and comprehensive analysis of sex differences in performance and performance-determining factors in the Olympic winter endurance sports. center dot Sex differences in competition speeds are similar to 7-16% in cross-country skiing, biathlon and speed skating, while no comparable data were available for Nordic combined or ski mountaineering. center dot Since men have historically skied and skated over greater distances than women in cross-country skiing, biathlon and speed skating competitions, the "true" sex differences in performance are likely larger than the differences reported in the literature, therefore exceeding the differences typically reported for summer endurance sports. center dot Most information about sex differences in Olympic winter endurance sports is based on studies performed in cross-country skiing. The conspicuous lack of information on Nordic combined and ski mountaineering warrants further research in these sports.