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Citation
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Gilgien M, Crivelli P, Kröll J, Luteberget LS, Muller E, Spörri J. Br. J. Sports Med. 2020; ePub(ePub): ePub. |
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Affiliation
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Center for Prevention and Sports Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland. |
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Abstract
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BACKGROUND/AIM: To set a safe giant slalom course, speed needs to be controlled in certain sections. Speed may be reduced by adjusting how the gates are set on a course. We studied the effect of elements of course-setting, entrance speed and terrain incline on the mechanics of turning (ie, turn speed, turn radius, and ground reaction force and impulse).
METHODS: During seven World Cup alpine giant slalom competitions, the course and terrain characteristics of the official racetracks and the mechanics of a professional-level athlete skiing the course immediately prior to competition were analysed with differential global navigation satellite system technology. Data were analysed using a linear mixed-effects model.
RESULTS: Course-setting geometry (vertical gate distance and horizontal gate offset), entrance speed and terrain incline modulated the injury-relevant factor turn speed. Depending on the terrain, the speed throughout a turn can be reduced by 0.5 m/s either by shortening the vertical gate distance by 4.9-6.9 m (from -20% to -29%) or by increasing the horizontal gate offset by 2.8-3.2 m (from +33% to +55%). However, increasing the horizontal gate offset causes the skier to turn with a smaller minimal turn radius, increase maximal ground reaction force and also increase impulse.
DISCUSSION: To reduce speed, we recommend decreasing the vertical gate distance rather than increasing the horizontal gate offset. Increasing horizontal gate offset would require the skiers to sharpen and prolong their turns (reducing turn radius), and this increases the acting ground reaction force and impulse and thus the athlete's fatigue.
© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.
Language: en |