INTRODUCTION: High external forces acting in alpine ski racing were published in several studies (Babiel et al. 1997, Mueller et al. 2002). As a consequence, alpine skiing athletes expend great effort to increase their muscular strength in conditioning training, accompanied by different methods of performance diagnostics (Mueller et al. 2002). This study attempts to compare, individually, the muscular abilities in lab with the demand on strength during competitive skiing, and tries to derive implications for safety and material considerations. METHOD: Seven male athletes of the German National Ski Team participated in the measurements. The mechanical load in alpine skiing (SL, GS, SG) was measured by pressure soles (Parotec, Paromed, Germany) in each boot and both knee angles by goniometers (Penny&Giles, UK). Data were stored in a data logger (Parotec, Paromed, Germany) and all runs recorded by video. Diagnostics on maximal isometric strength and concentric/eccentric strength abilities were performed on different knee angles (90°, 120°) and angular velocities (45°/s, 90 7s, 1807s) on a leg press (Desmotronic, Schnell, Germany). Using different custom built models, finally the muscular expenditure of individual force production in skiing was estimated (Spitzenpfeil et al. 2006). Based on the further estimation of ground reaction forces by GPS-data and video (see abstract Huber et al.), the muscular expenditures of racers during competition were assessed. RESULTS and DISCUSSION: First results show that in all measured cases the intensity of the estimated muscular expenditure in turns is higher than 50% of maximum in lab. The highest expenditure was recorded in SL with maximal intensities up to 100% depending on very low knee angles in some situations. However, the time of this maximum force production in SL is comparatively low. Averaging the values over 20s, the mean expenditure in all disciplines is about 40%. This indicates the high energy demands and needs of specific strength endurance abilities in alpine ski racing. The estimation of ground reaction forces by GPS-data and video of top racers in a GS show mean values around 2000 N and a maximum of 3500 N. Assuming the measured strength abilities of the subjects the overload in certain race situations can be anticipated. CONCLUSION: The estimation of muscular expenditure illustrates the well known importance of strength endurance abilities that should be considered in training. In combination with the estimation of ground reaction forces by GPS-data and video, the individual trajectory in a race course can be chosen dependent on the physical abilities of the racer. Inversely, these findings may influence future course settings.
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