ECSS Paris 2023: OP-AP35
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
Read CV Jonas ForotECSS Paris 2023: OP-AP35
INTRODUCTION: Performance development in elite cross-country skiing is primarily shaped during the general and specific preparation phases. However, limited evidence exists on which physiological and performance indicators change consistently from spring to fall, with only one previous study conducted in male skiers and restricted to a single season (Losnegard et al., 2013). This study quantified spring-to-fall changes in laboratory-based performance indicators in Swiss elite cross-country skiers over a 15-year period. METHODS: Retrospective longitudinal data from 81 male and 57 female Swiss elite cross-country skiers were analyzed across multiple seasons. Same-year spring-to-fall assessment pairs (spring: May–June; fall: September–October) were constructed for body fat percentage (BF%), fat-free mass (FFM), relative hemoglobin mass (HbM), relative VO₂max, relative power output at the second lactate threshold (LT₂), gross efficiency (GE), and squat jump peak power (SJ), yielding 1551 paired observations. Spring-to-fall changes were calculated as paired differences (fall − spring) and mean-based relative changes (%Δ). Statistical certainty was evaluated using linear mixed-effects models on changes (random intercepts for athlete and year), testing whether mean changes differed from zero. Standardized within-athlete effect sizes (d) were computed. RESULTS: BF% decreased significantly in men (−0.65 ± 1.46 %-points; −5.4%; d = −0.39; p = 0.006) but remained unchanged in women (+0.26 ± 1.67 %-points; +1.3%; p = 0.674). FFM increased modestly (women: +0.52 ± 1.02 kg; +1.1%; d = 0.47; p = 0.003; men: +0.29 ± 1.12 kg; +0.4%; d = 0.26; p = 0.008). Relative VO₂max increased significantly in both women (+1.55 ± 2.65 mL/kg/min; +2.7%; d = 0.49; p = 0.046) and men (+1.70 ± 2.15 mL/kg/min; +2.4%; d = 0.76; p = 0.002). LT₂ improved in both sexes (women: +0.08 ± 0.19 W/kg; +2.9%; d = 0.40; p = 0.005; men: +0.17 ± 0.20 W/kg; +4.7%; d = 0.74; p < 0.001). GE, relative HbM, and SJ showed small and statistically non-significant spring-to-fall changes (all p > 0.05). CONCLUSION: Spring-to-fall adaptations were most pronounced for aerobic performance, with typical improvements of approximately +2–3% in relative VO₂max and +3–5% in LT₂. FFM increased slightly (~0.4–1.1%), whereas BF% showed a meaningful reduction in men (~−5%) but remained stable in women. In contrast, GE, relative HbM, and SJ demonstrated limited seasonal change. These longitudinal reference values quantify the magnitude and statistical certainty of preparation-phase adaptations and provide a practical framework for interpreting routine testing results and defining realistic seasonal performance targets. REFERENCES: Losnegard, T., Myklebust, H., Spencer, M., & Hallen, J. (2013). Seasonal variations in VO2max, O2-cost, O2-deficit, and performance in elite cross-country skiers. J Strength Cond Res, 27(7), 1780-1790.
Read CV Elias BucherECSS Paris 2023: OP-AP35
INTRODUCTION: Ski mountaineering (SkiMo) sprint is a recently introduced Olympic discipline. The competition consists of a qualification round followed by knockout heats lasting ~2-3 minutes, with ~20-25 minutes of rest between. Each heat includes two uphill (U) skiing sections with skins, one foot part section, one downhill (D) skiing section, and three transition zones (T). This study aimed to identify performance determinants of SkiMo sprint during the Milan-Cortina Olympic Test Event by (1) analyzing section-specific contributions to overall sprint time (SPT), and (2) examining associations between the best uphill time excluding transitions (TSF) and laboratory-derived physiological parameters. METHODS: SPT and seven split times were analyzed during quarter-final for 36 qualified athletes. Section contributions to SPT variability were assessed using the covariance-to-variance ratio. Analyses were conducted separately for the top 18 seeded athletes (QF A) and those ranked 19-36 (QF B). Correlations between split times and SPT were computed across the entire sample. A subgroup of Swiss male SkiMo sprinters (n = 9; Tier 4-5) underwent laboratory testing. Aerobic and anaerobic capacities were assessed via an incremental test (GXT) and a time-to-exhaustion test at 120% of GXT maximum speed. Post-GXT passive blood lactate recovery was evaluated for 20 minutes (dBLarec). Associations between these variables and TSF were examined using correlation analyses and stepwise multiple regression (SMR). RESULTS: U time accounted for the largest proportion of SPT variability (81.5%) and was strongly correlated with SPT (r = 0.89, P < 0.0001), particularly during the first section of the race (r = 0.91, P < 0.0001). The first T showed a moderate association with SPT (r = 0.62, P < 0.05), whereas no significant associations were observed for the remaining U, T, or D sections. For QF A, T time contributed to a larger proportion of SPT variability than for QF B (46.8% vs. 18.4%). In Swiss athletes, TSF correlated with GXT maximal vertical velocity (r = -0.73, P < 0.05), and maximal oxygen uptake (VO2max) (ml/kg/min) (r = -0.73, P < 0.05) and SMR identified VO2max and dBLarec as the best TSF predictors (R2 = 0.82, P < 0.01). CONCLUSION: These findings indicate that sprint performance in elite SkiMo is largely determined by aerobic power supporting fast uphill sections, together with rapid race initiation. This aligns with determinants reported in cross-country sprint skiing, which shares a closely comparable competition format. Interestingly, dBLarec was also associated with sprint performance, suggesting a potential role of lactate shuttle capacity on fatigue resistance during a supramaximal SkiMo sprint. Finally, the relatively greater contribution of T to sprint performance among world-class athletes highlights that SkiMo sprint isn’t only about physiological capacity but also about highly efficient T under maximal effort.
Read CV Justin MottetECSS Paris 2023: OP-AP35