Movement analysis of cross-country ski techniques has always been of great importance due to its influence on skiing performance. Understanding how a skier moves through the space involves measuring and analyzing a great number of parameters describing linear and angular motion, velocity and acceleration of many body segments. Researchers have chosen different way to accomplish this task. In the last 5 years, a great number of investigations on biomechanics of cross country skiing have measured at least parameters of skiing cycle timing. About 40% reported data on pole force and on ski or plantar force, 20% investigated the muscle activation and 36% reported some data on upper or lower body angular kinematics. Some researchers have always tried to simplify the task of describing technical and biomechanical issue on cross country skiing by capturing an analyzing the motion of body center of mass (COM). COM is the point at which the entire weight of a body may be considered as concentrated. If the segments were rigid, the resultant of all forces acting on the body can be considered as applied on COM. The impossibility of directly measuring magnitude and point of application of forces involved in locomotion inspired many researchers to analyze COM motion to derive some mechanical aspect of animal and human movement [1]. Looking at COM, would mean catching the skiers whole motion and analyzing its acceleration would give an idea of the effect of the forces acting on him/her. The vertical range of motion of COM has been studied in some recent publication [2], [3]. Potential (PE) and kinetic (KE) energy associated to movement of body COM can be moreover computed from COM movement data. A further application, based on the work-energy principle, that states that the work done on an object is equal to the change in its energy [1], made it possible to approximately estimate the work required to move COM in different cross country skiing techniques and conditions. The analysis of the fluctuation of the energy of COM in cross country skiing has been recently adopted to identify the underling mechanism of classic technique. Kehler and coworkers [4] and Pellegrini and coworkers [5] observed that for diagonal stride (DS) PE and KE fluctuations were inphase making DS resemble the pattern of running, although a significant part of energy in DS is lost to rolling resistance [2]. Norman and Komi in 1987 [6] and Minetti and coworkers [7] years later, applied the work-energy principle to segment motion data of skiers on snow to estimated theirs mechanical output. Although part of the mechanical work done in skiing can be calculated by accounting for slope, average speed and friction; the additional calculation of the within-cycle COM displacements and speed fluctuations, although affected by some limitations and criticism, allow to reach a more complete estimation of the amount of mechanical work performed by the skier to sustain his/her locomotion with respect to the surroundings [3]. --- The hosting University of Jyväskylä is planning to publish conference proceedings "Science and Nordic Skiing III". In case you are interested in this publication please contact the editors (Anni Hakkarainen anni.s.j.hakkarainen@jyu.fi) to become registered for the book.
© Copyright 2015 3rd International Congress on Science and Nordic Skiing - ICSNS 2015. 5-8 June 2015, Vuokatti, Finland. Опубликовано по University of Jyväskylä; University of Salzburg. Все права защищены.