The effect of work rate on metabolic and mechanical intensity measures across skating style sub-techniques in cross-country skiing.

The purpose of this study was to examine how the work rate (WR) influences whole-body metabolic rate (MR) and more local measures of intensity (i.e., pole power, joint power, and triceps brachii (TB) and vastus lateralis (VL) tissue saturation index (TSI)) across skating style sub-techniques in cross-country skiing (XCS). Five-minute efforts were performed at a range of submaximal speeds at constant inclines of 2% for G4, 5% for G3, and 12% for G2. Pole forces and 3D motion capture were used to calculate pole, elbow, and shoulder power. TSI in the TB and VL muscles was measured using near-infrared spectroscopy. There was a significant interaction effect of WR and sub-technique on MR (p < 0.001), with a steeper slope in G4 followed by G3 and G2. Similar interaction effects were evident for shoulder power (p < 0.001), but neither for elbow power (p = 0.512) nor for arm or leg tissue saturation (p = 0.766). Relative pole and arm power contributions were independent of WR but differed between sub-techniques. Both VL and TB had greater TSI in G4 (p = 0.025) and G3 (p < 0.001), respectively, compared to G2, and the triceps brachii had a ∼15 ± 7% (p < 0.001) greater TSI than the vastus lateralis across sub-techniques. Differences in WR-induced responses on various metabolic and mechanical responses across sub-techniques demonstrate the necessity of a more nuanced view on exercise load and intensity, especially on the local joint and muscle level, in XCS.