INTRODUCTION: Force production plays an important role in diagonal skiing. A diagonal step can be divided into several phases (Komi and Norman 1987) and when the speed of a skier varies, produced forces may change according to speed. This study examined the effect of skiing speed on ski forces in diagonal skiing on a low uphill. METHOD: Eight top level young Finnish male skiers (age 17.211.0 yr, height 178.5±3.0 cm, body mass 71.6±6,8 kg) participated in this study. The ski forces (vertical (Fz) and horizontal (Fy) directions) on the right and left sides were recorded separately when the skier skied over a special custom made force-platform System (Neuromuscular Research Center, University of Jyväskylä). The entire system consisted of four separate 20 m long rows of one meter long force plates connected in series, row by row. The system was placed at the end of the uphill course on a stable 100 m long low uphill (2.5°) portion of a special indoor Ski Tunnel in Vuokatti Sports Institute (artificial snow, air temperature -4±0.5 "C, air humidity 84±4% and no wind) (Fig 1). RESULTS: F The analysis of the averaged ski forces was based on the modified functional phases from those of Komi and Norman (1987): 1) free gliding (1-2), 2) free glide and pole contact (2-3), 3) preloading for a kick (3-4) and 4) kick (4-5) phases (Fig 2). In the free gliding phase the ski Fz was highest in SLOW, and was subsequently reduced in MAX (Fig 3). The similar reduction occurred in the glide & pole phase (Fig 3). The reduction of the ski Fz from the free gliding to the glide & pole phase was 13±6, 13±4, 22+3, 32±2% (SLOW, MID, FAST, MAX, respectively). The negative ski Fy -and Fz values were similar in all skiing speeds (Fig 4). During the subsequent kick phase both the ski Fy and Fz increased significantly as function of the skiing speed. In the MAX condition, the averaged ski Fy and Fz during the kick phase were 150±41 and 1018±245 N, respectively. DISCUSSION:The present results, that the average Fz of the gliding and glide & pole phases decreased with higher skiing speed, can imply lower ski friction during the glide and glide & pole phases. The ski braking Fy and Fz during the pre-loading phase did not show any difference. That may give a Signal to the ski selection for top athletes that the pre competition ski selection, especially when testing grip qualities, could be done with medium or even low speed. In ski grip tests ski and wax properties play the major role for the ski selection, not speed of a skier.
© Copyright 2007 4th International Congress on Science and Skiing. Julkaistu Tekijä University of Salzburg. Kaikki oikeudet pidätetään. / Kääntänyt https://www.DeepL.com/Translator