title: Automatic Identification of Subtechniques in Skating-Style Roller Skiing Using Inertial Sensors.
abstract: This study aims to develop and validate an automated system for identifying skating-style cross-country subtechniques using inertial sensors. In the first experiment, the performance of a male cross-country skier was used to develop an automated identification system. In the second, eight male and seven female college cross-country skiers participated to validate the developed identification system. Each subject wore inertial sensors on both wrists and both roller skis, and a small video camera on a backpack. All subjects skied through a 3450 m roller ski course using a skating style at their maximum speed. The adopted subtechniques were identified by the automated method based on the data obtained from the sensors, as well as by visual observations from a video recording of the same ski run. The system correctly identified 6418 subtechniques from a total of 6768 cycles, which indicates an accuracy of 94.8%. The precisions of the automatic system for identifying the V1R, V1L, V2R, V2L, V2AR, and V2AL subtechniques were 87.6%, 87.0%, 97.5%, 97.8%, 92.1%, and 92.0%, respectively. Most incorrect identification cases occurred during a subtechnique identification that included a transition and turn event. Identification accuracy can be improved by separately identifying transition and turn events. This system could be used to evaluate each skier's subtechniques in course conditions.
authors.affiliation: Department of Sports Science, Japan Institute of Sports Sciences, 3-15-1 Nishigeoka, Kita-ku, Tokyo 115-0056, Japan. yoshihisa.sakurai@jpnsport.go.jp.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Sakurai
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192, Japan. zenya.fujita@aoni.waseda.jp.
authors.forename: Zenya
authors.initials: Z
authors.lastname: Fujita
authors.affiliation: Department of Sports Science, Japan Institute of Sports Sciences, 3-15-1 Nishigeoka, Kita-ku, Tokyo 115-0056, Japan. yusuke.ishige@jpnsport.go.jp.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ishige
keywords: accelerometer; cross-country skiing; gyroscope