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Repeated low impacts in alpine ski helmets
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.ORCID iD: 0000-0001-5234-6554
Swedish Winter Sports Research Center, MiUn.
KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.ORCID iD: 0000-0002-5819-4544
2013 (English)In: Sports Technology, ISSN 1934-6190, Vol. 6, no 1, 43-52 p.Article in journal (Refereed) Published
Abstract [en]

Alpine ski race helmets are subjected to multiple impacts during a race caused by the skiers hitting the gates on their way down the course. This study investigated the difference between expanded polystyrene (EPS) and expanded polypropylene (EPP) cores in alpine ski race helmets when subjected to repetitive violence, caused by alpine slalom gates. A special test rig was developed where a rotating slalom pole impacted the helmets with a velocity of 13.3 m·s- 1. All helmets (six EPS and six EPP) were attached to a headform, monitored with a triaxial accelerometer at the center of mass. Each helmet sustained 1000 impacts and acceleration data were collected around every 200 impacts. No significant differences were observed between the first hit and after 1000 hits for either the EPS or the EPP helmets. However, the total group mean acceleration and mean peak acceleration were 15% and 16% higher, respectively, for the EPS series compared with the EPP series. Also, all EPS helmets showed cracked cores after 1000 impacts compared with 1 cracked EPP core. Findings suggest that EPP cores might be more suitable for absorbing multiple low impacts caused by alpine gates and that repeated violence is a relevant parameter to consider when constructing alpine ski race helmets.

Place, publisher, year, edition, pages
2013. Vol. 6, no 1, 43-52 p.
Keyword [en]
head acceleration, alpine skiing, multiple impacts
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-103298DOI: 10.1080/19346182.2012.744413Scopus ID: 2-s2.0-84893933854OAI: oai:DiVA.org:kth-103298DiVA: diva2:559677
Note

QC 20130515

Available from: 2012-10-10 Created: 2012-10-10 Last updated: 2016-09-27Bibliographically approved
In thesis
1. Experimental test setups and simulations in skiing mechanics
Open this publication in new window or tab >>Experimental test setups and simulations in skiing mechanics
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Product testing and development are essential parts in sports and for the athletes in their quest to reach the podium. Manufacturers of sports equipment often use basic test methods which do not test the equipment in a sports specific way. Much of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. One short term aim was therefore to develop test methods for objective tests of sports equipment that also tested the equipment in a sports  specific  way.  Another  aim  was  to  integrate  mechanics  and  simulations  to  enhance  the understanding of the test results. The more long term aims are to contribute to increased theoretical knowledge regarding test methods for sports equipment and to contribute to the development of test  methods  to  create  new  and  better  sports  equipment.  Experimental  tests  combined  with simulations  can  give  valuable  information  to  improve  the  performance  and  safety  of  sports equipment. Three studies dealt with the issue of objective yet sport specific test methods for sports equipment. The main methodological advancement is the modification of established test methods together  with  conventional  mechanics  calculations.  New  test  devices  and  methodologies  are proposed for alpine ski helmets and cross-country ski poles. Suggestions are given for improved test setups as well as theoretical simulation are introduced for glide tests of skis. The results show how sport   specific   test   methodologies   together   with   theoretical   calculations   can   improve   the objectiveness and relevance when testing sports equipment. However, the collected and used data require high precision to obtain high accuracy in the simulations. High data accuracy can be an issue in field measurements but also due to manufacturers not disclosing key material data. Still, the used methods  and  calculations  in  this  thesis  produce  relevant  and  reliable  results  which  can  be implemented to accurate evaluations of different sports equipment. Even though it has not been a first priority aim in this work, the results from the alpine helmet study have been used by helmet manufacturers to design new helmets with increased safety properties. This further show how an objective and sport specific test approach together with theoretical simulation can improve sports equipment and in the longer perspective, also the athletes’ performances.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. v, 31 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2014:09
Keyword
sports equipment, test methods, sports mechanics, alpine skiing, cross-country skiing, poles, helmets, glide, performance
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-144408 (URN)
Presentation
2014-04-29, Sal D3, Lindstedtsvägen 5, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20140423

Available from: 2014-04-23 Created: 2014-04-22 Last updated: 2014-04-23Bibliographically approved
2. 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.
Series
TRITA-MEK, ISSN 0348-467X ; 2016-13
Keyword
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
Identifiers
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)
Opponent
Supervisors
Note

QC 20160927

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

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Swarén, MikaelEriksson, Anders

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