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Validation of test setup to evaluate glide performance in skis
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. Mid Sweden University, Sweden.
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. Mid Sweden University, Sweden.ORCID iD: 0000-0002-5819-4544
2014 (English)In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 7, no 1-2, 89-97 p.Article in journal (Refereed) Published
Abstract [en]

Although today's ski waxing chemicals and micro-machining techniques of the ski base are highly sophisticated, objective procedures for testing and verification of the results have not yet been developed and evaluation is based on comparison of subjective experience. The purpose of the present study was thus to compare different setups for testing the glide of cross-country skis. Two differently waxed ski pairs were tested for glide inside a ski tunnel. Inertial measurement units (IMUs) were attached to each ski; instantaneous velocities monitored by three different speed-traps; the velocities during the acceleration phase determined by Doppler radar. Kinetic, potential and total energy, giving the energy dissipation, were calculated for four representative trials during the acceleration phase. No reliable data were obtained from the IMUs due to high drift. The mean maximal velocity for the two ski pairs were 6.97, s = 0.09 and 6.70, s = 0.09 m·s − 1, respectively. Higher differences between the skis were identified during the retardation phase compared to the acceleration phase. The mean difference between the velocities determined by the speed-trap and Doppler radar was 0.6, s = 1%, demonstrating that the latter provides accurate data for evaluation of gliding characteristics and performance. However, theoretical confirmation of the friction coefficient, on the basis of data provided by Doppler radar and energy calculations requires exact measurements of the inclination and topography of the track in question.

Place, publisher, year, edition, pages
Routledge, 2014. Vol. 7, no 1-2, 89-97 p.
Keyword [en]
alpine, cross-country, friction, skiing, snow, wax
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-176220DOI: 10.1080/19346182.2014.968164ScopusID: 2-s2.0-84938955462OAI: diva2:871608

QC 20151116 QC 20160923

Available from: 2015-11-16 Created: 2015-11-02 Last updated: 2016-09-27Bibliographically approved
In thesis
1. Objective Analysis Methods in the Mechanics of Sports
Open this publication in new window or tab >>Objective Analysis Methods in the Mechanics of Sports
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sports engineering can be considered as the bridge between the knowledge of sports science and the principles of engineering and has an important role not only in improving the athletic performance, but also in increasing the safety of the athletes. Testing and optimization of sports equipment and athletic performance are essential for supporting athletes in their quest to reach the podium. However, most of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. Consequently, one of the aims of this thesis was to combine mechanics and mathematics to develop new objective test methods for sports equipment. Another objective was to investigate the possibility to accurately track and analyse cross-country skiing performance by using a real-time locating system. A long term aim is the contribution to increased knowledge about objective test and analysis methods in sports. The main methodological advancements are the modification of established test methods for sports equipment and the implementation of spline-interpolated measured positioning data to evaluate cross-country skiing performance. The first two papers show that it is possible to design objective yet sport specific test methods for different sports equipment. New test devices and methodologies are proposed for alpine ski helmets and cross-country ski poles. The third paper gives suggestions for improved test setups and theoretical simulations are introduced for glide tests of skis. It is shown, it the fourth paper, that data from a real-time locating system in combination with a spline model offers considerable potential for performance analysis in cross-country sprint skiing. In the last paper, for the first time, propulsive power during a cross-country sprint skiing race is estimated by applying a power balance model to spline-interpolated measured positioning data, enabling in-depth analyses of power output and pacing strategies in cross-country skiing. Even though it has not been a first priority aim in this work, the results from the first two papers have been used by manufacturers to design new helmets with increased safety properties and cross-country ski poles with increased force transfer properties. In summary, the results of this thesis demonstrate the feasibility of using mechanics and mathematics to increase the objectiveness and relevance when analysing sports equipment and athletic performance.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 32 p.
TRITA-MEK, ISSN 0348-467X ; 2016-13
sports equipment, test methods, sports mechanics, biomechanics, performance analysis, tracking, positioning system, pacing, alpine skiing, cross-country skiing, poles, helmets
National Category
Engineering and Technology
urn:nbn:se:kth:diva-193044 (URN)978-91-7729-094-0 (ISBN)
Public defence
2016-10-20, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)

QC 20160927

Available from: 2016-09-27 Created: 2016-09-27 Last updated: 2016-09-27Bibliographically approved

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