Introduction: The trunk plays a crucial role in the power production during double poling (Hegge et al., 2015), one of the main subtechniques in classical cross-country skiing. While intense whole-body exercise has been shown to result in general fatigue and reduced performance, the effect of fatigue in more isolated components of the relevant muscle chains is less understood. Therefore, the aim of this study was to investigate acute effects of a fatigued trunk on double poling performance and pacing strategy in junior cross-country skiers. Methods: 16 well-trained male junior cross-country skiers completed two identical pre- and post-tests on separate days in a randomized, controlled cross-over design. In between pre- and post-test, either a 25-min fatiguing exercise sequence targeting the core musculature (FAT) or a 25-min resting control condition (CON) were applied. Performance tests consisted of a maximal isometric trunk strength tests (flexion and extension; IsoMed 2000 backmodule; D&R Ferstl, Hemau, Germany), followed by a 3-min self-paced double poling test (SkiErg; Concept2, Morrisville, VT, USA). Power output, cycle characteristics and cardiorespiratory variables were continuously measured during the double poling test. Results: Isometric peak torque during trunk flexion (-63%) and extension (-11%) decreased in FAT (both p < 0.001) and was unchanged in CON (p = 0.39 and p = 0.42). Trunk fatigue led to a 13% decrease in mean power output (mean pre-post change: -32 (95% CI -41,-23) W; p < 0.001), whereas power did not change in CON (+2%; p = 0.21). Cycle rate decreased by 10% in FAT (-0.11 (-0.14,-0.08) Hz; p = 0.001) and by 5% in CON (-0.06 (-0.09,-0.02) Hz; p = 0.005). Peak heart rate did not differ between FAT and CON (-1%; p = 0.10 and +1%; p <0.001). Peak oxygen uptake decreased by 4% in FAT (p = 0.004) and increased by 3% in CON (p = 0.027). Peak ventilation decreased by 7% in FAT (p < 0.001) and did not differ in CON (0%; p = 0.59). Pacing analysis showed the greatest power reduction during the first 60 s in FAT (-64 W; p < 0.001), with less reductions in the second 60 s (-31 W; p <0.001) and no difference in the third 60 s (-3 W; p = 0.524). Discussion: Acute fatigue of core muscles in junior cross-country skiers resulted in substantial decreases in power output and altered pacing profiles during double poling. The accompanied reduction in respiratory capacity after fatigue indicates a close tie between trunk control, respiration and performance in double poling.
© Copyright 2016 21st Annual Congress of the European College of Sport Science (ECSS), Vienna, 6. -9. July 2016. Veröffentlicht von University of Vienna. Alle Rechte vorbehalten.