ANALYSIS OF THE HANDS SUPPORT IN EXTRA-PLUMMET CLIMBING SKILL
AbstractINTRODUCTION-The purpose of this study is to compare the hands support behaviour in two different extra-plummet climbing skills (as performed in climbing walls with angles between horizontal below 90°). These two extra-plummet climbing skills can be distinguished by basic body positions. Taking the pressure centre of hands support as reference the body balance is considered a stable balance because the hands have a higher positions than the feet. (Jodar, 1993). Therefore the level of body stability in these two skills, depends, basically, on the performers capacity of maintaining body contact with the wall by means of the hand grip. (Vert>ier, 1991). The capacity to maintain the hand's grip is the result of the relationship between friction force and the tangential forces applied by the c1imber on contact surface. The two studied skills have different basic body positions: in skill A tha basic body position is "body are" and in skill B the basic body position is "body suspense”. Taking the mathematical expression of friction force into account, the access to the behaviour of the friction force can be achieved through normal force (Hammil & Knutzen, 1995). Thus, the hand's support stability is accomplished by the quotient of each tangential and normal force appfied by the climber on contact with the surface. The registration of force values (Fx is the force acting in parallel direction to the sagittal plan, Fy is the force acting in parallel direction to the frontal plan and Fz is the normal force) in both skills and was achieved through the Kistler platform, model 9281 Sand appropriate software, fixed horizontally on an artificial climbing wall. RESULTS-The sample was composed of eight experimented c1imbers whose ages ranged from twenty-two to forty years old. Every subject performed five valid executions in both skills. In skill A, the arithmetical mean of Fx/Fz was 0,372, CV=0,352, and the arithmetical mean of Fy/Fz was 0,009, CV=6,83. In skili S, the arithmetical mean of Fx/Fz was 0,25, CV=0,311, and the arithmetical mean of Fy/Fz was 0,017, CV=1,089. The statistical method T of Pairs was applied to evaluate the differences between Fx/Fz data in both skills and also to evaluate the differences between Fy/Fz data in the same skills. CONCLUSIONS-The results give evidence that the values of Fy/Fz do not differ between the studied skills, but the value of Fx/Fz in skill S was significantly different from skill A. Therefore skill B has a greater potential to be used in further climbing skills, because it uses a smaller percentage (~25%) of normal force than skill A (~37,2%). REFERENCES• Hamill, Joseph; Knutzen, Kathleen M. (1995). Biomechanical Basis of Human Mouvement. Williams & Wilkins. Philadelphia. USA. 403-405. J6dar, Xavier Aguado (1993) Eficacia Y Teeniea Deportiva. INDE. Barcelona. Epana. 178-186. Verdier, Jean-Pierre (1991). Initiation et Perfectionement ä Esca/ade. Amphora. Paris. Franee. 29-36.
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