Effect of an intense period of competition on race performance and self-reported illness in elite cross-country skiers.

Aim: To determine whether participating in a cross-country skiing stage race (TDS) affects subsequent illness incidence, training and race performance. Methods: Self-reported training and illness data from 44 male and female elite cross-country skiers were included. In total, 125 years’ of data was collected (2-3 seasons per athlete). Illness incidence, training load and performance in international competitions were calculated for athletes who did and did not participate in TDS. Results: 48% of athletes reported becoming ill during or in the days immediately after taking part in TDS, vs. 16% of athletes who did not participate. In both groups, illness incidence was somewhat lower for female athletes. For male athletes, race performance was significantly worse for 6 weeks following TDS vs. 6 weeks before TDS. Furthermore, while female athletes who participated in TDS performed relatively better than controls in Olympics/World Championships, male athletes who participated in TDS typically performed worse in subsequent major championships. Conclusion: Participating in TDS appears to result in ~3-fold increase in risk of illness in this period. Male athletes appear more prone to illness and also see a drop in race performance following TDS, possibly linked to differences in training load before and after the event.