The impact of cross-country skiers’ tucking position on ski-camber profile, apparent contact area and load partitioning

Abstract

In cross-country skiing races, the difference between the fastest and the second fastest time can be minuscule. As in all endurance sports, cross-country skiing requires the use of energy to overcome resistive forces, in this case primarily aerodynamic drag and friction between the skis and snow. Even a slight reduction in either of these can determine the outcome of a race. The geometry of the ski exerts a profound influence on the friction between the skis and snow. As a result of the flexible modern cross-country skis, the camber profile and gliding properties to be influenced by the skiers’ position. Here, based on the location of the normal force corresponding to the plantar pressure, we characterize the ski camber while performing three variations of the downhill tucking position. We found that when gliding on a classic ski, the risk of contact between the kick wax and snow can be reduced by tucking in a leaning backwards position (i.e. by moving the skier’s center of mass backwards). With the tucking position, the percentage of the skier’s body weight that is distributed onto the friction interface at the rear of the skis varies between 63.5% in Gear 7 (leaning forward) on a skating ski and 93.0% in Gear 7 (leaning backwards) on a classic ski.

Characterisation of the Contact between Cross-Country Skis and Snow: On the Multi-Scale Interaction between Ski Geometry and Ski-Base Texture

“…The macro-scale contact mechanical responses of two pairs of classical skis, named "Ski A" and "Ski B", both with the width of 44 mm, considered in the present work were simulated under a load equivalent to 40 kg placed 1.6 dm behind the balance point. The reason for choosing this loading condition is that it was found, in [15], to be the equivalent load corresponding to the neutral G7 position for a skier of 80 kg in body weight. The results, in terms of H and P, are depicted in Figure 2.…”

“…Given an equivalent load (magnitude and position), corresponding to the plantar pressure exerted by the athlete, that, during, e.g., tucking downhill, represents half the skier's body weight applied 16 cm behind the balance point [15], an ANN can be employed to predict the geometry of the ski-camber profile as a function of the coordinate along the ski. Hence, the predicted ski-camber profile may be used as input in the BEM-based model presented in [18] to simulate the macro-scale contact between the ski-camber profile and virtual snow.…”

“…When trying to estimate friction in cross-country skiing, it is crucial to consider the entire ski. The macro-scale geometry of the ski, under a given loading condition, can be measured using profilometry; see, e.g., [15]. The resulting ski-camber profile features the front and the rear contact zones, as well as the camber between them, and it is often used to determine how well suited a ski is for a particular condition.…”

“…They observed an increase in stiffness and shorter contact zones as the temperature decreased. Recently, Kalliorinne et al [15] showed how skiers' pose during tucking influences the length of the rear and front contact zones, as well as the load partitioning between them.…”

Characterisation of the Contact between Cross-Country Skis and Snow: A Micro-Scale Study Considering the Ski-Base Texture

“…Other models [10][11][12], including the authors' previous work [13,14], have only considered the apparent area of contact, an approach that completely neglects the influence of the preparation of the ski base. Recently, Lever and colleagues [15] utilised a setup involving a rotating disc to observe the thermal and mechanical characteristics of polyethylene in sliding contact with snow.…”