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

Abstract

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. Ten competitive cross-country skiers (6 males; O2max 78 ± 3 and 4 females; O2max 62 ± 3mL∙kg-1∙min-1) raced time trials consisting of 1, 2, and 4laps in a 1.6km racecourse in a randomized order with 35min 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 O2max 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. Average oxygen demand was 112 ± 8%, 103 ± 7% and 98 ± 7% of O2max during the 1 (3:37 ± 0:20m:ss), 2 (7:36 ± 0:38m:ss) and 4 (15:43 ± 1:26m: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 O2max, respectively). Accumulated oxygen deficit at the end of each time trial was 85 ± 13, 106 ± 32 and 158 ± 62mL∙kg-1, while oxygen deficits per work bout was 23 ± 3, 18 ± 3 and 16 ± 3mL∙kg-1 for the 1, 2, and 4-lap time trials, respectively. 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.