INTRODUCTION: Group comparisons across conditions are commonly used to justify generalizations about human responses. In sport biomechanics such comparisons may enhance understanding of some relationships while ignoring uniquety individual responses. To better understand individual characteristics for purposes of improving performance, single-subject analysis may provide insights concerning an individual's strengths, weaknesses and strategies for using capabilities optimally (Bates, 1996). This approach was applied in slalom racing using ski reaction force data from individual elite skiers. METHODS: Ski reaction forces were recorded during simulated slalom ski competitions. High level Norwegian skiers (n = 9) were tested during a training camp. Two slalom courses were set side-by-side on a moderate slope with minimal side gradient. Courses had consistent 10 and 13 m spacings between gates. Forces were recorded from Novel Pedar insoles and saved to a portable data logger at 50 Hz. Ten turns (5 left, 5 right) near the middle of each course were analyzed. Gate passage and turn transitions in time were identified with synchronized video. Timing of reaction forces was evaluated from apex of the force and its timing within the turn cycle. Ratio of Inside-to-Outside ski forces were determined from impulse of force over the turn cycle for each ski. Single-subject comparisons were made for each skier using 5 trials each of Inside/Outside ski characteristics, for Left and Right turns, and for 10 and 13m courses. RESULTS and DISCUSSION: Representative ski reaction force-time traces are shown in Figure 1. Mean apex forces were about 2.3 ± 0.2 body weights across skiers. Considerable differences were observed from skier to skier. Some exhibited substantially greater loading of the Outside ski (Figure 1B) while others had similar loadings between skis (Figure 1C). For the skier shown, turn direction affected force distribution between skis, likely due to a previous knee injury. Some skiers had clear asymmetries side-to-side. 5 skiers had greater total forces in one direction; 5 had earlier apex timing in Left turns; 6 skiers had greater Inside/Outside ratio when turning either toward the dominant side or away from the injured side. CONCLUSION: Analyzing skier reaction forces individually rather than as a group, provides important understanding of a skier's technical weaknesses and adaptation to previous injury.
© 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.