INTRODUCTION: One of the continuously discussed problems in alpine skiing is the turn decomposition into single phases (Müller et al., 1998; Raschner et al., 2001, and others). When decomposing the turn, authors mostly use kinematic or dynamic analysis, but exact expression of the time duration of the phases has not been defined. This paper presents a method that allows total time duration of the turn and its initiation and steering phases definition, based on dynamometric reaction force record. METHODs: Quantitative expression of the two turn phases is based on dynamometric measurement of the reaction force Fz (t) upright to the ski plane, physical forces System, skier's weight, and slope declination. The method is presented on example analysis of 36 carving turns performed by six skilled skiers, RESULTS: A key result of the study is a method for exact expression of single phases of the turn formulation. An inter-individual variability analysis (n = 36 symmetrical carving turns) resulted in quantitative data concerning time duration and percentage ratio of the initiation (37 ± 7 %) and steering (63 ± 7 %) phase related to the turn total duration, DISCUSSION: A mathematical analysis confirmed suitability of application of constant slope angle (a = 25,6°, cos a = 0,9) and skier's weight. A relatively simple mathematical expression allows, after the mentioned data Substitution, derivation of total turn duration and time of the initiation and steering phase based on dynamometrical record of the reaction force F2 (t) upright to the ski plane. The proposed method, even concerning obtained results relativity, offers possibilities for exact solution of other different problems concerning the turn performance. CONCLUSION: The proposed method enables objective evaluation of turn and its Initiation and steering phase duration based on dynamometrical record of the reaction force Fz (t). First results of the symmetrical carving turn analysis proved initiation and steering phase ratio (37 ± 7 % and 63 ± 7 %, respectively) out of the complete turn duration. Further use of the method in the alpine skiing research can expected.
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