Author(s): MORTON, S., MACPHERSON, T., FORREST, L., EASTON, C., Institution: UNIVERSITY OF THE WEST OF SCOTLAND, Country: UNITED KINGDOM, Abstract-ID: 2458

INTRODUCTION:
Maximal oxygen uptake (VO2MAX) is important for endurance sports [1] like cross-country skiing (XCS). Studies correlate VO2MAX with XCS performance [2], but meta-analyses are challenging, perhaps due to variation in study methods and performance level definitions [3]. The aim of this review was to compare VO2MAX across performance tiers from a Participant Classification Framework (PCF) [3] and identify potential research gaps.
METHODS:
A systematic search of databases up to November 2023 was conducted to assess physiological outcomes and XCS performance, focusing on the predictive value of VO2MAX. Blind study screening and PCF scoring were performed by two investigators. Random-effects meta-analyses were utilized to calculate pooled PCF group means and 95% confidence intervals. Subsequent multiple meta-regressions were conducted to assess variances, with tau and R2 reported to explain variance in VO2MAX due to PCF. Heterogeneity was assessed using tau2.
RESULTS:
70 studies were reviewed, separated by VO2MAX protocol and sex. A meta regression was conducted for running protocols (Males: 41 studies; n= 623; Females: 22 studies; n= 289). PCF explained 49% of the variance in VO2MAX in males (tau= 6.14, R2= 0.49). Group means increased with PCF (PCF: 1= 53.7ml.kg-1.min-1 CI: 46.8-60.9; 2= 66.0ml.kg-1.min-1 CI: 57.7-74.1; 3= 71.1ml.kg-1.min-1 CI: 69.0-73.3; 4= 76.0ml.kg-1.min-1 CI: 74.1-78.0; 5= 82.5ml.kg-1.min-1 CI 79.7-85.2; tau2= 37.7). In females, PCF explained 56% of variance in VO2MAX (tau= 4.80, R2= 0.56). VO2MAX group means also increased with PCF (PCF: 1= 44.6ml.kg-1.min-1 CI: 42.2-47.0; 2= 57.2ml.kg-1.min-1 CI: 54.2-60.3; 3= 61.4ml.kg-1.min-1 CI: 59.3-63.5; 4= 65.4ml.kg-1.min-1 CI: 63.4-67.4; 5= 70.4ml.kg-1.min-1 CI 69.1-71.7; tau2= 23.0). Further meta-analyses were conducted in males, with limited PCF tiers, for VO2MAX methods using Double Poling (DP) Ski Ergometer (SkiErg): ‘Whole Body’ (PCF range 2-4), Diagonal Stride (DS) (PCF range 2-5) and V2 (PCF range 3-5). For DP SkiErg Whole Body, VO2MAX increased across the PCF range analysed. In DS, VO2MAX also increased with PCF, with the exception of an elevated tier 2, calculated from just 1 study (67.2ml.kg-1.min-1 CI: 65.7-68.7). In V2, VO2MAX increased between tier 3 and 4, but no further increase was observed between tier 4 and 5 (4= 71.0ml.kg-1.min-1 CI: 67.1-74.9; 5= 70.9ml.kg-1.min-1 CI: 69.7-71.2). Data were lacking for further detailed analyses in females.
CONCLUSION:
VO2MAX increased across PCF tiers in methods analysed, except in the DS and V2 technique. The exception in DS may be explained by the low number of tier 2 studies included. VO2MAX, as measured in running, also increased with PCF tier in females. Where low study numbers were present, PCF tiers may be underrepresented; these findings should be interpreted with caution. Further research including females, ski specific techniques, and application of PCF assessment in XCS is required.

[1] Joyner and Coyle, 2008
[2] Carlsson et al. 2016
[3] McKay et al. 2022