Skating in cross-country skiing has developed into several distinctive techniques which are used under differing conditions. The V1 and V2 techniques are widely used by skiers for uphill and flat terrain skating. In this respect, these techniques function much like gears do for cycling. Just as an optimal choice of gearing can enhance a cyclist's performance, skating "gear choice" may affect various characteristics which influence a skier's performance. Treadmill testing of skating has compared V1 and V2 techniques for various physiological characteristics on several slopes (Kvamme et al., 2005; Losnegard et al., 2012) but measurements on snow are more difficult. In the current study undertaken during a world cup ski race, a transition zone where both V1 and V2 skating were being used allowed comparison of the techniques under race conditions. Mechanical energy analyses of human locomotion provide insights concerning energy exchanges which potentially affect economy of motion. Walking and running provide clear mechanisms which allow humans to move with relatively low cost. In walking, exchanges of potential (PE) and kinetic energy (KE) require little mechanical work during a cycle, similar to the exchanges for an inverted pendulum. In contrast, during running little exchange between PE and KE occurs but instead energy is stored elastically in "leg springs" (Farley & Ferris, 1998). In skiing, only limited energy analyses have been carried out. Pellegrini et al. (2013) analyzed classical skiing techniques. Based on PE and KE fluctuations, pendulum-like exchanges of energy during double poling were observed. In contrast, diagonal stride energy patterns allowed little exchange between PE and KE. Kehler et al. (2014) calculated PE and KE using reaction forces while diagonal striding on an instrumented treadmill. In-phase changes of PE and KE were observed (like running) but during glide nearly all KE decreases were attributable to frictional losses rather than elastic storage. Thus diagonal stride was different from both walking and running. The purpose of the current study was to analyze energy fluctuation patterns for ski skating on uphill terrain where racers were using both V1 and V2 techniques. Magnitudes and timing of PE and KE changes were evaluated to gain insight about the transition from V2 to V1 that all skiers made during the hill climb. In addition, energy conservation mechanisms such as seen for walking and running were evaluated for each of the skating techniques. (Original introduction)
© Copyright 2016 Sciene and nordic skiing III. Published by University of Jyväskylä; University of Salzburg. All rights reserved.