INTRODUCTION: The mechanical properties of a ski can considerably influence the performance and sensations felt by skiers (Fischer et al., 2007). It remains unknown whether laboratory measurements can enable one to predict the behaviour of a ski when it is being used on the snow. The purpose of the present study was to develop a method for measuring ski deformation during skiing and to quantify the influence of snow strength and loading condition on ski deformation. METHOD: An expert skier was asked to perform the same GS-slalom run several times. The skier used an alpine ski instrumented with eight strain gauges positioned at different locations on the ski for the determination of bending and torsional deformation. The measuring frequency of the strain gauges was set to 200 Hz. The applied force perpendicular to the ski was measured with PEDAR® pressure insoles. The snow strength was measured with the Snowmicropen®. During the active phase of each carved turn, the mean, the maximum and the Standard deviation of the deformation for each sensor were determined. Additionally, a Fourier transformation of the Signals was made to determine the resonance frequencies. RESULTS: The mean bending deformation of the middle part of the ski was 55 mm for the outside ski and 38 mm for the inside ski. Mean twist angles of 1 ° for the rear part and 0.8° for the front part of the ski were measured. High maximum values and Standard deviation of twist angles were measured on hard snow. DISCUSSION: It could be shown that snow strength significantly influences ski deformation in torsion. The bending deformation is more dependent on the applied load than on the snow strength. The position of the skier significantly modifies the deformation of the ski. CONCLUSION: A method was developed to measure at high frequency ski deformation in bending and in torsion on the field. In the future, this measuring technique should be used to quantify the influence of different ski constructions on their mechanical behaviour on the field and correlate these results with the performance and subjective judgments of athletes.
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