INTRODUCTION: The friction between Ski and snow is an important element to accelerate the kick of the stance phase of classicai technique cross-country (x-c) skiing. It has been shown that with increasing skiing speed, the pole force contribution decreased (Vähäsöyrinki et al, submitted). However, relatively little is known how skiers compensate the x-c ski locomotion under different wax conditions. The purpose of the present study was to examine effects of different grip wax on the pole and ski forces together with muscle activities. METHOD: Eight young male skiers were asked to ski at maximal ski speed (MAX) with three different wax conditions (no grip wax (SLIP), poor grip wax (POOR), and good grip wax (GOOD) conditions). Thereafter they skied at the 3 different submaximal target speeds (65, 75, and 90% of their WAX skiing speed) (Table 1). The ski and pole forces (vertical (Fz) and horizontal (Fy) directions) on the right and left sides were recorded separately over the custom made 20m long force-platform System together with the electromyographic activities (EMG) of leg and arm muscles. RESULTS: Figure 1 shows typical examples of time course data of the ski steps at MAX with three grip wax conditions. With better grip wax conditions, the averaged ski Fy during the braking phase and the averaged kicking Fy during the kicking phase were greater but the pole Fy was smaller (p<0.05) (Figurel). In the phase-averaged EMG analysis during the braking and kicking phases, there were no significant differences in leg muscles between varied wax conditions. DISCUSSION/CONCLUSION: The present study confirms earlier suggestions (Komi 1987) that with better grip wax and faster ski speed condition the contribution of the pole Fy can be smaller. It is likely that skiers can increase the pole forces to reach the higher Ski speed instead of increasing the ski kicking force under the SLIP and POOR wax conditions. However, the muscle activities of the leg muscles remain the same between varied wax conditions. The grip wax dependence of the ski and pole force distributions in the present study are important for further understanding of the complexity of x-c skiing.
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