INTRODUCTION: Macro parameters of cross-country skiing, e.g. sub-technique classification, is thoroughly studied. However, detailed analysis of within-cycle movement of a sub technique, the micro parameters, have only been investigated on treadmills or with roller skis 1,2,3. We bring the lab-to-the-field and investigate the micro parameters of the diagonal stride in cross-country skiing while skiing on snow. We investigate the movement of the ski during the diagonal stride by mounting inertial measurement units (IMUs) on the skis. The first aim of this study was to automatically detect sub-phases of diagonal stride skiing on snow, specifically the sub-phases; glide, thrust and recovery. The second aim was to explore how these sub-phases are affected by changing from conventional- to running-style diagonal stride. METHODS: IMU sensors recording accelerometer and gyroscope data at 256 Hz were mounted on the skis in front of the binding supplemented with a ground truth video. Data was recorded from 9 athletes performing conventional diagonal stride, and compared to an athlete performing both conventional- and running-style diagonal stride. The data were analyzed in MATLAB using an analysis refined from [1]. RESULTS: The plots illustrate three cycles from the resulting acceleration curves along the direction of the movement of the ski, as well as the estimated velocity, with the vertical lines indicating the automatic detection of transition between sub-phases. The top plot is from conventional and the lower is from running-style diagonal stride. DISCUSSION/CONCLUSION: We can observe that running diagonal significantly reduces the length of the gliding sub-phase, and also has a more noisy transition into the thrust sub-phase.
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