INTRODUCTION: So far the analysis of the skiing techniques in alpine skiing has been often limited to the use of optical video based methods. Due to the ongoing miniaturization, the application of inertial measurement systems (IMS) is becoming increasingly practicable. The investigations of Brodie et al. (2008) and Supej (2007) examined the application of a full body IMS for the determination of kinematic parameters in alpine skiing. However, a quantitative validation of a full body IMS for the application in a real skiing environment is so far not available. The purpose of this study was to determine the accuracy of a full body inertial measurement system for the application in alpine skiing in comparison to an optical video based system. METHOD: A ski instructor equipped with a full body IMS (120 Hz, Moven, Xsens Technologies, The Nethertands) performed a test-run on a well prepared slope. A DGPS (GPS1200, Leica Geosystems, Switzerland) was additionally used to determine the absolute position of the skier in space. One turn of the test-run was filmed by 4 synchronized cameras (50 Hz). Markers were manually digitized in the lab using Simi Motion Software (Simi Reality Motion Systems, Germany). Kinematical parameters of both systems were calculated. The knee angle, the tilting angle, and the speed of the knee joint were analyzed. RESULTS & DISCUSSION: The maximum mean deviation between the IMS and the optical system in regard to the measured angles showed a value of 4,9° (0,4°). A high correlation coefficient of 0.95 was found. Thus, a reason for the deviation might be a systematic error (e.g. misalignment of the marker). In regard to the edging angle a maximum mean deviation of 3.3° was measured. The analysis of trajectories by using the IMS solely is not possible. By means of the additional usage of the DGPS the absolute position of the skier in space can be calculated. CONCLUSION: With an IMS, the analysis of kinematical parameters in a real skiing environment with a reasonable accuracy is provided. Compared to optical methods the main advantages of the system are the measurement without a restricted capture volume, and small time costs for the measurement preparation and data analysis. Nevertheless, depending on the conditions while skiing (snow conditions, skiing speed etc.) a varying measurement accuracy might be observed.
© Copyright 2010 Book of Abstracts. 5th International Congress on Science and Skiing, Dec. 14 - 19, 2010, St. Christoph am Arlberg. Veröffentlicht von University of Salzburg, Interfakultärer Fachbereich Sport- und Bewegungswissenschaft/USI. Alle Rechte vorbehalten.