INTRODUCTION: "Modern" double poling (DP), introduced by Holmberg et al. (2005), is the most used technique in the classical cross-country skiing sprint (XCSS) competitions. However, there is no published data about how pole forces change during XCSS using DP due to fatigue. The aim of this study was thus to investigate changes in pole forces and cycle characteristics during XCSS. METHOD: Twelve Finnish top-level male XC skiers performed a simulated sprint competition (4 x 1050 m heat / 20 min recovery between heats) using DP technique in an indoor ski tunnel on snow. Vertical (Fz) and horizontal (Fy) pole forces, as well as poling (PT), recovery (RT) and cycle times (CT = PT + RT) were measured using a custom made 18-m-long force plate System (Vähäsöyrinki et al. 2008) during the start (maximal), race (optimal race speed) and finish (maximal) phases of each heat. Furthermore, vertical (Iz) and horizontal (ly) pole impulses, DP speed (V18m) and cycle length (CL) were calculated. Velocity (VH), heart rate (HR) and peak lactate (LA) were also measured during the heats. RESULTS: VH decreased by 2.5% (p<.01) from heat1 (6.1 ±0.3 m/s) to heat4 (5.9±0.3 m/s) but there were no changes in HR (from 180±4 to 179±5 bpm) or LA (from 11.2+1.1 to 11.6±1.8 mmol/l) between the heats. V18m and cycle characteristics did not differ when comparing the same phases between the heats but when averaging all four heats significant changes were observed within phases (table 1). The poling forces and impulses decreased within the heats (table 1) but not between the heats. The mean VH of four heats correlated significantly to the mean V18m of the race (r=.91***) and finish (r=.79**) phases as well as to the mean Fy of the finish phase (r=.70*) and to the mean Fz of the race phase (r=.59*). DISCUSSION/CONCLUSION: Decreased maximal DP velocity (V18m) within heats (start vs. finish phase) indicated fatigue among the skiers. Fatigue was manifested by decreased pole force production and changes in cycle characteristics. However, the accumulation of fatigue between the heats was minor because of the 20-min recovery between the heats. Also, the skiers' different pacing strategies might affect the accumulation of fatigue. The fastest sprint skiers seemed to be able to keep propulsive force levels higher during the finishing sprint
© Copyright 2010 Book of Abstracts. 5th International Congress on Science and Skiing, Dec. 14 - 19, 2010, St. Christoph am Arlberg. Published by University of Salzburg, Interfakultärer Fachbereich Sport- und Bewegungswissenschaft/USI. All rights reserved.