INTRODUCTION: The performance of a cross-country (XC) ski is multifaceted and individual-specific. Consequently, ski-selection is often done by subjective assessment. Differentiating skis based on feeling is an arduous skill susceptible to individual bias. The aim of this study was to develop a sensor-based solution to augment subjective assessments of XC-skis. METHODS: Three skiers rated four pairs of skis on a 1.0 km lap. The skiers wore inertial measurement units and a GNSS receiver as described in Tjønnås (2019). The ski`s within-cycle kinematics in diagonal stride were calculated as described by Fasel et al. (2015). Each skier subjectively rated three ski-performance factors, "glide", "lead" and "grip", on an interval scale. Rated "glide" was compared to ski friction coefficient, which was estimated in a downhill segment by considering changes in mechanical energy and estimating air drag. Rated "lead" was compared to the ski`s deceleration during the glide phase of diagonal stride (Fig. 1). Rated "grip" was compared to peak negative ski-velocity during diagonal stride (occurring directly after the leg push, Fig. 1). Agreement between subjective rating and microsensor measurement was evaluated by Pearson`s correlation coefficient for each skier separately and reported as the range over all skiers. RESULTS: There were high correlations between rated "glide" and measured friction coefficient (r = 0.79-0.94), and between "lead" and deceleration during the glide phase (r = 0.71-0.77). Correlations between rated "grip" and measurements of peak negative ski speed were variable (r = -0.35-+0.40). DISCUSSION/CONCLUSION: Our results indicate that differences in XC-skis gliding properties, both during bilateral ("glide") and unilateral ("lead") stance, can be detected using microsensors on skis and athlete. The skis grip could not be detected with the proposed feature.
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