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Open AccessArticle

A Magnet-Based Timing System to Detect Gate Crossings in Alpine Ski Racing

1
Archinisis GmbH, 1700 Fribourg, Switzerland
2
Laboratory of Movement Analysis and Measurement, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
3
Department of Orthopedics, Balgrist University Hospital, University of Zurich, 8008 Zurich, Switzerland
4
Department of Sport Science and Kinesiology, University of Salzburg, 5400 Hallein-Rif, Austria
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(4), 940; https://doi.org/10.3390/s19040940
Received: 28 January 2019 / Revised: 20 February 2019 / Accepted: 20 February 2019 / Published: 22 February 2019
(This article belongs to the Special Issue Wearable Sensors for Gait and Motion Analysis 2018)
In alpine skiing, intermediate times are usually measured with photocells. However, for practical reasons, the number of intermediate cells is limited to three–four, making a detailed timing analysis difficult. In this paper, we propose and validate a magnet-based timing system allowing for the measurement of intermediate times at each gate. Specially designed magnets were placed at each gate and the athletes wore small magnetometers on their lower back to measure the instantaneous magnetic field. The athlete’s gate crossings caused peaks in the measured signal which could then be related to the precise instants of gate crossings. The system was validated against photocells placed at four gates of a slalom skiing course. Eight athletes skied the course twice and one run per athlete was included in the validation study. The 95% error intervals for gate-to-gate timing and section times were below 0.025 s. Each athlete’s gate-to-gate times were compared to the group’s average gate-to-gate times, revealing small performance differences that would otherwise be difficult to measure with a traditional photocell-based system. The system could be used to identify the effect of tactical choices and athlete specific skiing skills on performance and could allow a more efficient and athlete-specific performance analysis and feedback. View Full-Text
Keywords: gate crossing; alpine skiing; slalom; giant slalom; validation; performance; timing; magnet gate crossing; alpine skiing; slalom; giant slalom; validation; performance; timing; magnet
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MDPI and ACS Style

Fasel, B.; Spörri, J.; Kröll, J.; Müller, E.; Aminian, K. A Magnet-Based Timing System to Detect Gate Crossings in Alpine Ski Racing. Sensors 2019, 19, 940.

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