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Automatic classification of the sub-techniques (gears) used in cross-country ski skating employing a mobile phone
Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Sport Science and Kinesiology, University of SalzburgHallein/Rif, Austria . (Swedish Winter Sports Research Centre)ORCID iD: 0000-0002-6685-1540
School of Computer Science and Communication, Royal Institute of Technology, Stockholm, Sweden .
Swedish Institute of Computer Science, Kista, Sweden.
Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. (Swedish Winter Sports Research Centre)
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2014 (English)In: Sensors, ISSN 1424-8220, Vol. 14, no 11, 20589-20601 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the current study was to develop and validate an automatic algorithm for classification of cross-country (XC) ski-skating gears (G) using Smartphone accelerometer data. Eleven XC skiers (seven men, four women) with regional-to-international levels of performance carried out roller skiing trials on a treadmill using fixed gears (G2left, G2right, G3, G4left, G4right) and a 950-m trial using different speeds and inclines, applying gears and sides as they normally would. Gear classification by the Smartphone (on the chest) and based on video recordings were compared. Formachine-learning, a collective database was compared to individual data. The Smartphone application identified the trials with fixed gears correctly in all cases. In the 950-m trial, participants executed 140 ± 22 cycles as assessed by video analysis, with the automatic Smartphone application giving a similar value. Based on collective data, gears were identified correctly 86.0% ± 8.9% of the time, a value that rose to 90.3% ± 4.1% (P < 0.01) with machine learning from individual data. Classification was most often incorrect during transition between gears, especially to or from G3. Identification was most often correct for skiers who made relatively few transitions between gears. The accuracy of the automatic procedure for identifying G2left, G2right, G3, G4left and G4right was 96%, 90%, 81%, 88% and 94%, respectively. The algorithm identified gears correctly 100% of the time when a single gear was used and 90% of the time when different gears were employed during a variable protocol. This algorithm could be improved with respect to identification of transitions between gears or the side employed within a given gear.

Place, publisher, year, edition, pages
2014. Vol. 14, no 11, 20589-20601 p.
Keyword [en]
Algorithm, Collective classification, Gaussian filter, Individual classification, Machine learning, Markov chain, Smartphone
National Category
Sport and Fitness Sciences Signal Processing Telecommunications
URN: urn:nbn:se:miun:diva-23789DOI: 10.3390/s141120589ISI: 000345562800038ScopusID: 2-s2.0-84908530187OAI: diva2:772081
Available from: 2014-12-16 Created: 2014-12-16 Last updated: 2015-01-05Bibliographically approved

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Stöggl, ThomasAndersson, ErikHolmberg, Hans-Christer
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