A Biomechanical Approach to Paralympic Cross-Country Sit-Ski Racing

Objective: To analyze the biomechanics of the double poling gesture in cross country disable sit–skiers in the field during competition. Design: Elite athletes were recorded during the 1 km sprint race with a high speed markerless stereo photogrammetric camera system. Reference points were semi-automatically tracked frame-by-frame on video images, according to a biomechanical model consisting of seven anatomical and four technical points. Coordinates of points were evaluated for 2D kinematic analysis of the push gesture both in a word and sledge reference frames. Setting: Winter Paralympic Games, Vancouver 2010, Canada. Subjects: Paralympic athletes: 35 men and 15 women; classified in all the five classes of the sit skiers category. Results: Several graphical results represent the development of the double poling gesture of each athlete with respect to both world reference and sledge reference frames. The progression of the gesture is depicted by: body and pole stick diagrams, trends of reference points positions and their gradients, and body joints trajectories in space. In addition, kinematic biomechanical parameters, such as joints ROM, and technical parameters, such as pole incline and sledge velocity, are reported. Conclusions: This research demonstrates the feasibility of a markerless kinematic analysis of the poling gesture on a contest field. Results point out a wide variability of the gesture due to the residual functional capabilities and sitting postures of each athlete. However the poling cycles of subjects classified into different classes present similar features. An original segmentation of the double poling gesture in a sequence of three phases is proposed in the paper.