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Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System
Department of Physical Performance, Norwegian School of Sport Sciences, Sognsveien 220, Oslo 0806, Norway
Department of Sport Science and Kinesiology, University of Salzburg, Schlossallee 49, Hallein/Rif 5400, Austria
Laboratory of Movement Analysis and Measurement, Ecole Polytechnique Fédérale de Lausanne, Station 11, Lausanne 1015, Switzerland
* Author to whom correspondence should be addressed.
Received: 1 July 2013; in revised form: 22 July 2013 / Accepted: 29 July 2013 / Published: 2 August 2013
Abstract: In alpine ski racing the relationships between skier kinetics and kinematics and their effect on performance and injury-related aspects are not well understood. There is currently no validated system to determine all external forces simultaneously acting on skiers, particularly under race conditions and throughout entire races. To address the problem, this study proposes and assesses a method for determining skier kinetics with a single lightweight differential global navigation satellite system (dGNSS). The dGNSS kinetic method was compared to a reference system for six skiers and two turns each. The pattern differences obtained between the measurement systems (offset ± SD) were −26 ± 152 N for the ground reaction force, 1 ± 96 N for ski friction and −6 ± 6 N for the air drag force. The differences between turn means were small. The error pattern within the dGNSS kinetic method was highly repeatable and precision was therefore good (SD within system: 63 N ground reaction force, 42 N friction force and 7 N air drag force) allowing instantaneous relative comparisons and identification of discriminative meaningful changes. The method is therefore highly valid in assessing relative differences between skiers in the same turn, as well as turn means between different turns. The system is suitable to measure large capture volumes under race conditions.
Keywords: force; kinetics; kinematics; GPS; global navigation satellite system; technical validation; precision; alpine skiing
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Gilgien, M.; Spörri, J.; Chardonnens, J.; Kröll, J.; Müller, E. Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System. Sensors 2013, 13, 9821-9835.
Gilgien M, Spörri J, Chardonnens J, Kröll J, Müller E. Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System. Sensors. 2013; 13(8):9821-9835.
Gilgien, Matthias; Spörri, Jörg; Chardonnens, Julien; Kröll, Josef; Müller, Erich. 2013. "Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System." Sensors 13, no. 8: 9821-9835.