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  • Preventing injuries in alpine skiing giant slalom by shortening the vertical distance between the gates rather than increasing the horizontal gate offset to control speed

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Original research
Preventing injuries in alpine skiing giant slalom by shortening the vertical distance between the gates rather than increasing the horizontal gate offset to control speed
  1. Matthias Gilgien1,2,
  2. Philip Crivelli3,
  3. Josef Kröll4,
  4. Live S Luteberget1,
  5. Erich Müller4,
  6. Jörg Spörri5,6
  1. 1 Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
  2. 2 Center of Alpine Sports Biomechanics, St Moritz Health and Innovation Foundation, Samedan, Switzerland
  3. 3 Group for Snowsports, WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland
  4. 4 Department of Sport Science and Kinesiology, University of Salzburg, Hallein-Rif, Austria
  5. 5 Sports Medical Research Group, Department of Orthopaedics, Balgrist Balgrist University Hospital, University of Zurich, Zurich, Switzerland
  6. 6 Center for Prevention and Sports Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
  1. Correspondence to Matthias Gilgien, Department of Physical Performance, Norwegian School of Sport Sciences, Oslo 0806, Norway; matthias.gilgien{at}nih.no

Abstract

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.

  • injury prevention
  • elite performance
  • alpine skiing
  • global positioning system
  • knee

https://doi.org/10.1136/bjsports-2019-101692

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    Footnotes

    • Contributors MG, JS, JK and EM conceptualised the study design. MG, JS and JK organised and coordinated the biomechanical data collections at the FIS WC races. MG, PC and LSL conducted the data processing, statistical analysis and data interpretation. MG and JS drafted the first version of the manuscript. All authors contributed to the intellectual content of the study, manuscript writing and approved the final version of this article.

    • Funding This study was financially supported by the International Ski Federation (FIS) Injury Surveillance System (ISS). The funding source had no involvement in the study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit this paper for publication.

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Patient consent for publication Not required.

    • Ethics approval This study was approved by the Ethics Committee of the Department of Sport Science and Kinesiology at the University of Salzburg. All subjects provided written informed consent prior to participating in the investigation.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information. Access to the data underlying the study is restricted due to intellectual property reasons.