Validation of portable 2D force binding systems for cross-country skiing

Abstract

The aim of the present study was to design, construct, and scientifically validate a two-dimensional force measurement binding system for cross-country skiing. The system consists of two force measurement bindings. One binding was designed for analysing classic skiing (vertical and anterior-posterior [along the ski] force components) and the other one for skate (freestyle) skiing (vertical and medio-lateral [transverse to the ski] force components). Validation was accomplished by using a three step process 1) accuracy tests for the sensors in two temperatures, 2) sport-specific imitation jump test on standard force plates in a laboratory and 3) comparing the system against force measurement reference systems that are currently used when skiing on snow. During sport-specific imitation jumps, differences in peak forces and impulses between the classic binding and the reference systems ranged from 8.0 % to 19.9 % and were two to three times greater compared to differences between the skate binding and the reference systems (range: -5.9 to 5.5 %).However, high similarity coefficients were observed with both bindings (classic binding: 0.990 to 0.996; skate binding: 0.996 to 0.999) compared to the reference systems. Based on these results, the skate binding was shown to be fully valid for use in field measurements of skate skiing, whereas some improvements have to be performed in the construction and sensor placements for the classic binding (vertical as well as anteriorposterior force component).

Forces and mechanical energy fluctuations during diagonal stride roller skiing; running on wheels?

“…Although we used a different methodology, the general shapes of the roller skiing ground reaction forces were quite comparable to traces previously reported for on-snow skiing (Komi, 1987;Vähäsöyrinki et al, 2008), force instrumented roller skis (Bellizzi et al, 1998;Ohtonen et al, 2013) and force instrumented poles (Lindinger et al, 2009;Pellegrini et al, 2011;Stöggl and Holmberg, 2011). Also, the forces we recorded for walking and running were consistent with previously reported values (Nilsson and Thorstensson, 1989).…”

“…Black arrows indicate how the change in the rate of kinetic energy (ΔKE/Δtime) decrease during the glide phase was calculated. Lindinger et al, 2009;Ohtonen et al, 2013;Pellegrini, 2011;Stöggl and Holmberg, 2011;Vähäsöyrinki et al, 2008). However, to our knowledge, none have integrated the forces to calculate the COM energy fluctuations.…”

Forward acceleration of the centre of mass during ski skating calculated from force and motion capture data

“…Due to problematic and limiting mechanical cross talk that produced less accurate anteriorposterior forces along the ski in earlier versions of a 3D force binding [34], two custom-made 2D force measurement bindings for XC skiing (Neuromuscular Research Centre, University of Jyväskylä, Finland) with a weight of 490 g each were built to measure GRFs at 1000 Hz. Force bindings were calibrated using special calibration devices and procedures [14]. One pair of prepared racing skis (Peltonen Supra-x, Peltonen Ski Oy, Hartola, Finland, 188 cm, 1170 g each) was used by all skiers.…”

“…3c) of selected racing poles adjusted to the preferred length of each skier. Calibration of the pole sensors was processed with standard procedures in accordance with previous studies [35][36][37]. The validity of the system was examined on an established force platform system (Neuromuscular Research Centre, University of Jyväskylä, Finland) [9].…”

“…[10]) were measured directly by two-dimensional (2D) or 3D force platforms placed in or under the snow. More recently, models for calculating the propulsive components from ground reaction forces (GRFs) and 3D kinematics measured with improved and miniaturized systems during roller ski skating [11][12][13][14] were developed. With this approach, the share of the resultant GRF pointing in the desired skiing direction was calculated by taking into account the ski orientation, ski edging angle, and track incline and the corresponding pole angles (e.g.…”