The influence of race duration on oxygen demand, uptake and deficit in competitive cross-country skiers

Abstract Purpose To measure oxygen demand, uptake, and deficits in competitive cross-country skiers during outdoor roller skiing at different competition durations, ranging from the endurance domain to the sprint domain. Methods Ten competitive cross-country skiers (6 males; V̇ V ˙ O 2max 78 ± 3 and 4 females; V̇ V ˙ O 2max 62 ± 3 mL∙kg −1 ∙min −1) raced time trials consisting of 1, 2, and 4 laps in a 1. 6 km racecourse in a randomized order with 35 min recovery in-between. Oxygen uptake was measured using a wearable metabolic system while oxygen demand was estimated from kinematic data (GPS and IMU) and an athlete-specific model of skiing economy. Skiing economy and V̇ V ˙ O 2max was established on a separate test day using six submaximal constant-load trials at different speeds and inclines, and one maximal-effort trial on a roller-skiing treadmill. Results Average oxygen demand was 112 ± 8%, 103 ± 7% and 98 ± 7% of V̇ V ˙ O 2max during the 1 (3: 37 ± 0: 20 m: ss), 2 (7: 36 ± 0: 38 m: ss) and 4 (15: 43 ± 1: 26 m: ss) lap time trials, respectively, and appeared to follow an inverse relationship with time-trial duration. Average oxygen uptake was unaffected by race length (86 ± 5%, 86 ± 5%, and 86 ± 7% of V̇ V ˙ O 2max, respectively). Accumulated oxygen deficit at the end of each time trial was 85 ± 13, 106 ± 32 and 158 ± 62 mL∙kg −1, while oxygen deficits per work bout was 23 ± 3, 18 ± 3 and 16 ± 3 mL∙kg −1 for the 1, 2, and 4-lap time trials, respectively. Conclusion Elite cross-country skiers adjust their pacing strategies from attaining relatively small oxygen deficits per work bout in the endurance domain, to larger deficits in the sprint domain. This indicates a shift in strategy from prioritizing stable work-economy and rate-of-recovery in the endurance domain, to maximizing power output in the sprint domain.