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

Caroline Göpfert,Stefan J Lindinger,Walter Rapp,Olli Ohtonen,Vesa Linnamo,Mikko V Pohjola

doi:10.1007/s12283-016-0223-9

Caroline Göpfert, Stefan J Lindinger + Show 4 more

Open Access

https://doi.org/10.1007/s12283-016-0223-9

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Abstract

The purpose of this paper was to present and evaluate a methodology to determine the contribution of bilateral leg and pole thrusts to forward acceleration of the centre of mass (COM) of cross-country skiers from multi-dimensional ground reaction forces and motion capture data. Nine highly skilled cross-country (XC) skiers performed leg skating and V2-alternate skating (V2A) under constant environmental conditions on snow, while ground reaction forces measured from ski bindings and poles and 3D motion with high-speed cameras were captured. COM acceleration determined from 3D motion analyses served as a reference and was compared to the results of the proposed methodology. The obtained values did not differ during the leg skating push-off, and force–time curves showed high similarity, with similarity coefficients (SC) >0.90 in the push-off and gliding phases. In V2A, leg and pole thrusts were shown to contribute 35.1 and 65.9% to the acceleration of the body, respectively. COM acceleration derived from ground reaction forces alone without considering the COM position overestimated the acceleration compared to data from motion analyses, with a mean difference of 17% (P < 0.05) during leg push-off, although the shapes of force–time curves were similar (SC = 0.93). The proposed methodology was shown to be appropriate for determining the acceleration of XC skiers during leg skating push-off from multi-dimensional ground reaction forces and the COM position. It was demonstrated that both the COM position and ground reaction forces are needed to find the source of acceleration.

Highlights

Aided by various tools, human locomotion is highly versatile, allowing us to move effectively on dry land and snow, in and on water, and even through the air
centre of mass (COM) acceleration derived from ground reaction forces alone without considering the COM position overestimated the acceleration compared to data from motion analyses, with a mean difference of 17% (P \ 0.05) during leg push-off, & Caroline Gopfert caroline.goepfert@stud.sbg.ac.at
During self-propelled locomotion, the propulsion must be created by muscular force and transmitted to the environment in a manner that leads to movement in the desired direction

Summary

Introduction

Human locomotion is highly versatile, allowing us to move effectively on dry land and snow, in and on water, and even through the air. During self-propelled locomotion, the propulsion (i.e. forces produced by the leg, trunk, and/or arms that lead to motion forward [1]) must be created by muscular force and transmitted to the environment in a manner that leads to movement in the desired direction. Good performance requires high energetic capacity and the ability to produce considerable propulsion effectively and economically [4, 5], while forces are transmitted to the ground through skis and poles when using different techniques. The propulsive force of XC skiing has been defined as the component of the three-dimensional (3D) resultant reaction force from each pole and/or ski in a forward direction acting on the skier [6].

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