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Article

A Novel Sensor Foil to Measure Ski Deflections: Development and Validation of a Curvature Model

1
Department of Sport and Exercise Science, University of Salzburg, Schlossallee 49, 5400 Hallein/Rif, Austria
2
Joanneum Research Forschungsgesellschaft mbH, Franz-Pichler-Straße 30, 8160 Weiz, Austria
3
Atomic Austria GmbH, Atomic Strasse 1, 5541 Altenmarkt, Austria
4
Athlete Performance Center, Red Bull Sports, Brunnbachweg 71, 5303 Thalgau, Austria
*
Author to whom correspondence should be addressed.
Academic Editor: Giuseppe Vannozzi
Sensors 2021, 21(14), 4848; https://doi.org/10.3390/s21144848
Received: 1 June 2021 / Revised: 6 July 2021 / Accepted: 14 July 2021 / Published: 16 July 2021
(This article belongs to the Special Issue Sensor Technology for Sports Monitoring)
The ski deflection with the associated temporal and segmental curvature variation can be considered as a performance-relevant factor in alpine skiing. Although some work on recording ski deflection is available, the segmental curvature among the ski and temporal aspects have not yet been made an object of observation. Therefore, the goal of this study was to develop a novel ski demonstrator and to conceptualize and validate an empirical curvature model. Twenty-four PyzoFlex® technology-based sensor foils were attached to the upper surface of an alpine ski. A self-developed instrument simultaneously measuring sixteen sensors was used as a data acquisition device. After calibration with a standardized bending test, using an empirical curvature model, the sensors were applied to analyze the segmental curvature characteristic (m−1) of the ski in a quasi-static bending situation at five different load levels between 100 N and 230 N. The derived curvature data were compared with values obtained from a high-precision laser measurement system. For the reliability assessment, successive pairs of trials were evaluated at different load levels by calculating the change in mean (CIM), the coefficient of variation (CV) and the intraclass correlation coefficient (ICC 3.1) with a 95% confidence interval. A high reliability of CIM −1.41–0.50%, max CV 1.45%, and ICC 3.1 > 0.961 was found for the different load levels. Additionally, the criterion validity based on the Pearson correlation coefficient was R2 = 0.993 and the limits of agreement, expressed by the accuracy (systematic bias) and the precision (SD), was between +9.45 × 10−3 m−1 and −6.78 × 10−3 m−1 for all load levels. The new measuring system offers both good accuracy (1.33 × 10−3 m−1) and high precision (4.14 × 10−3 m−1). However, the results are based on quasi-static ski deformations, which means that a transfer into the field is only allowed to a limited extent since the scope of the curvature model has not yet been definitely determined. The high laboratory-related reliability and validity of our novel ski prototype featuring PyzoFlex® technology make it a potential candidate for on-snow application such as smart skiing equipment. View Full-Text
Keywords: bending sensors; flexion; PyzoFlex; ski bending; ski deflection bending sensors; flexion; PyzoFlex; ski bending; ski deflection
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MDPI and ACS Style

Thorwartl, C.; Kröll, J.; Tschepp, A.; Schäffner, P.; Holzer, H.; Stöggl, T. A Novel Sensor Foil to Measure Ski Deflections: Development and Validation of a Curvature Model. Sensors 2021, 21, 4848. https://doi.org/10.3390/s21144848

AMA Style

Thorwartl C, Kröll J, Tschepp A, Schäffner P, Holzer H, Stöggl T. A Novel Sensor Foil to Measure Ski Deflections: Development and Validation of a Curvature Model. Sensors. 2021; 21(14):4848. https://doi.org/10.3390/s21144848

Chicago/Turabian Style

Thorwartl, Christoph, Josef Kröll, Andreas Tschepp, Philipp Schäffner, Helmut Holzer, and Thomas Stöggl. 2021. "A Novel Sensor Foil to Measure Ski Deflections: Development and Validation of a Curvature Model" Sensors 21, no. 14: 4848. https://doi.org/10.3390/s21144848

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