In the Olympic winter sports cross-country skiing and the biathlon, athletes aim to minimise resistive forces such as aerodynamic drag, gravity, and ski–snow friction to enhance performance. Ski–snow friction is complex, involving multiple friction mechanisms that vary depending on snow conditions. In cold environments, where the moisture and water content are minimal, friction is presumably influenced primarily by dry interactions between the ski and snow, particularly through adhesion and abrasion at the micro-scale. Here, we examined ski–snow friction under cold conditions using eight pairs of cross-country skis, with different apparent contact lengths and real contact areas. Our findings revealed that apparent contact length, a macro-scale parameter, had the greatest impact on friction, followed by total real contact area, which is a multi-scale parameter. For snow temperatures below approximately −10 °C, longer apparent contact lengths reduced friction, whereas shorter lengths are more effective above −10 °C. In addition, at −3 °C, minimising the total real contact area was advantageous for reducing friction, while this effect diminished at −8.5 °C. At the coldest tested temperature of −13 °C, a larger total real contact area resulted in the lowest friction. These findings highlight the importance of considering both macro- and micro-scale contact properties for optimising ski performance in different cold conditions.

In cross-country skiing, athletes expend large amounts of energy to overcome friction as their skis interact with snow. Even minor reductions in the friction can significantly influence race outcomes. Over the years, researchers have found many ways of quantifying ski–snow friction, but there are only a few methods that consider the glide of real-sized skis under natural conditions during both accelerating and decelerating movements. This study introduces a novel experimental setup, consisting of a sled equipped with authentic cross-country skis and a base station that uses satellite receivers to communicate via radio, constituting a real-time kinematic positioning system with centimetre accuracy. While the sled was running on a classic ski track with natural height variations, altitude and velocity data were recorded for quantification of the coefficient of friction (COF), both for accelerating and decelerating motion, employing a model based on Newton’s second law. The results show that the COF during acceleration was more than 20% higher than during deceleration, demonstrating dynamic changes in the frictional behaviour between these phases. This finding is crucial for the execution of all types of cross-country skiing techniques, where the athlete either accelerates or decelerates while moving forward. The ability of the current experimental set-up to distinguish between the COF during acceleration and deceleration has considerable implications for further developments.