Author(s): FOROT, J., BOURDILLON, N., BROCHERIE, F., MILLET, G.P., Institution: CENTRE NATIONAL DE SKI NORDIQUE ET DE MOYENNE MONTAGNE, Country: FRANCE, Abstract-ID: 2426

INTRODUCTION:
The physiological characteristics of elite sprint- and distance-specialized cross-country (XC) skiers have been widely investigated (1). Oxygen uptake (V̇O₂) kinetics reflects the dynamic adjustment of oxidative metabolism to changes in exercise intensity and is an important, yet often overlooked, determinant of endurance performance (2). However, contrary to many other endurance sports, data on V̇O₂ kinetics in elite XC skiers remain scarce. Therefore, the aim of this study was to characterize and compare V̇O₂ kinetics in elite sprint- and distance-specialized XC skiers.
METHODS:
Male elite XC skiers of the French national-team classified as highly trained (Tier 3, n = 7, age = 18.4 ± 1.1), international level (Tier 4, n = 7, age = 26.7 ± 4.1) or world-class (Tier 5, n = 5, age = 26.9 ± 3.9) (3) performed two repeated square-wave transitions from standing rest to moderate-intensity treadmill roller-ski skating, followed by an incremental test to exhaustion. Breath-by-breath V̇O₂ was time-aligned, averaged across transitions, and fitted with a mono-exponential model to derive primary-phase amplitude (A) and time constant (τ).
RESULTS:
Sprint-specialized male skiers exhibited slower V̇O₂ kinetics than distance specialists, as reflected by a longer τ (24.1 ± 4.8 vs. 17.8 ± 3.8 s; p = 0.013), while A was similar between specializations (28.3 ± 2.0 vs. 27.4 ± 3.5 mL·kg⁻¹·min⁻¹; p = 0.508). The τ value was significantly lower (p < 0.05) in Tier 3 XC skiers (11.8 ± 8.2 s) compared with Tier 4 (20.4 ± 2.4 s) and Tier 5 (24.5 ± 1.0 s), likely due to the significantly younger age (p < 0.01) of the Tier 3 group. No significant differences were observed for maximal oxygen uptake (V̇O₂max) between sprint- and distance-specialized males (77.8 ± 2.5 vs. 79.7 ± 5.8 mL·kg⁻¹·min⁻¹; p = 0.334).
CONCLUSION:
This study provides the first sport-specific examination of V̇O₂ kinetics in elite XC skiers and demonstrates a significant difference in aerobic adjustment dynamics between sprint- and distance-specialized athletes, despite similar V̇O₂max values. Interestingly, fast V̇O₂ kinetics was observed in elite distance- XC skiers (17.8 ± 3.8 s), in line with values reported in other elite endurance athletes (e.g., τ = 13.9 s in Olympic champion rowers) (4). These findings suggest that V̇O₂ kinetics captures physiological dimensions that are partly independent from maximal aerobic capacity and may complement V̇O₂max in the profiling of XC skiers. Further research is needed to determine whether incorporating V̇O₂ kinetics improves performance prediction and training prescription in this population.

Keywords: V̇O₂ kinetics; cross-country skiing; performance tiers; primary phase

References
1. Losnegard, Hallen. (2014) Int J Sports Physiol Perform, 9, 25-31
2. Poole, Jones. (2012) Compr Physiol, 2, 933-96
3. McKay, et al. (2022) Int J Sports Physiol Perform, 17, 317-31
4. Ingham, et al. (2007) Med Sci Sports Exerc, 39, 865-71