INTRODUCTION: During the last decade, double poling (DP) became a main classical technique in cross-country (XC) ski racing. Optimized skiing equipment, better training methods and the sprint discipline led to altered demands and increased focus on DP development. Holmberg et al. (2005) described modern DP characteristics with distinct lower body work, shorter poling times, higher forces and thus a more explosive push-off. So a further question is, how elite skiers control DP speed. Earlier DP studies found increased poling frequencies (Pf) and maintained or decreased cycle lengths (CL) across velocities (Hofmann et al. 1995; Millet et al. 1998; Nilsson et al. 2004) suggesting to primarily adjust Pf as the mechanism of speed control. Besides speed-cycle relationships, no other kinematic and only few kinetic aspects have been analyzed. Purpose of the current study was to perform a detailed analysis of speed increase strategies during DP in modern elite XC skiers. METHOD: 12 elite XC skiers roller skied using DP at five treadmill velocities (9, 15, 21, 27, maximal velocity [Vmax: 29.5±1.3 km-h-1]). Joint angles (Goniometer; Megatron, Germany) and axial pole forces (strain gauge system) were measured by Biovision-System (Werheim, Germany) and proceeded by IKE-Master-Software (Salzburg, Austria). Repeated ANOVA were calculated to analyze changes in all variables across speeds (statistical level P<0.05). RESULTS: CL and Pf increased through 27 km-h-1 and V^* (P<0,05). At submaximal veiocities (Vsm) absolute poling time (PT) shortened to 0.28± 0.03s, PPF and rate of force development in-creased two- and four-fold (P<0.05), all with no change up to Vmax, Hip and knee angle (HA; KA) at pole plant, minimal EA, HA and KA during poling phase (PP) decreased, and elbow fiexion amplitude (AMPLEflex) with all angular joint flexion velocities (AVflex) increased over Vsm (e.g. AVEflex: 344± 150°-s-1; P<0.05), but then maintained. AVEext (548± 105°-s"1), AMPLHext and AMPLKext during recovery phase (RP) increased through 27 km-h-1 (P<0.05). Starting from a constant "high-hip position" in RP, AMPLHflexRp, AMPLKflexRp and total AVHflex and AVKflex (angtemaxRp to angteminpp) increased across Vsm (P<0,05), with no change at Vmax. DISCUSSION/CONCLUSION: Today's top skiers control DP speed by increasing both CL and Pf, which is novel. The faster they go, they show a higher and more explosive force production during shortened and more accentuated stretch-shortening cycles (arm and shoulder), connected with increasingly extensive leg work and use of body weight (increasing flexion-extension) across velocities. The tremendous decrease of PT (<0.28s) and time to PPF (<0.08s) at Vmax, challenges specific neuromuscular abilities in modern skiers. Future technique and strength training concepts should consider these aspects.
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