THE RELATIONSHIP BETWEEN SELECTED KINEMATIC PARAMETERS AND LENGTH OF JUMPS OF THE SKI-FLYING COMPETITION

Transcription

1 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 THE RELATIONSHIP BETWEEN SELECTED KINEATIC PARAETERS AND LENGTH OF JUPS OF THE SKI-FLYING COPETITION Jaez Vodičar ad Boja Jošt Faculty of Sport, Uiversity of Ljubljaa, Ljubljaa, Sloveia Origial scietific paper UDC :577.3:531.1 Abstract: The objective of this study was to aalyse selected kiematic parameters (time of flyig, i-ru velocity, take-off velocity, out-ru velocity, height of flyig at 17 m, height of flyig at 75 m, height of flyig at 120 m, aerodyamic idex at 17 m, aerodyamic idex at 75 m, aerodyamic idex at 120 m) of the best world-class ski jumpers participatig i the two fial idividual competitios (Friday ad Suday) of the Ski-Flyig World Cup at Plaica, Sloveia i 2009 (HS 215 m). All jumps were recorded with three video cameras operatig at 50 fps, followig the jumpers at the early flight phase (17 m from the take-off edge) ad i the middle phase of flyig (75 m ad 120 m from the take-off edge). The ski jumpers were divided ito three statistically sigificatly differetiated quality groups accordig to their jump legths i all three rouds (F prob. =.01). By meas of correlatio aalysis ad sigle-factor aalysis of variace, a smaller umber of statistically sigificat correlatios betwee the defied kiematic variables ad the jump legth were determied. The differeces i the vertical height of flyig cofirmed a tedecy towards positive correlatios betwee this variable ad the jump legth (r mi =.42, r max =.79). The group of the best ski jumpers demostrated a statistically sigificat higher vertical height of flyig curve i all the three competitive rouds at the poits of 75 m (F prob. were betwee.00 ad.08) ad 120 m (F prob. =.01). The best group of ski jumpers had better aerodyamic positios i the flight phase, especially at the poit of 75 m (Suday, the first roud, r =-.73; p =.00) ad 120 m (Suday competitio i both rouds, F prob. =.01). Key words: ski jumps, kiematic flight aalysis, Fial World Cup Competitio 2009, Plaica HS 215 m Itroductio The competitio i the fials of the 2009 World Cup i Ski Flight was selected to ivestigate the kiematic factors of the techiques used by ski jumpers o the ski flyig jumpig hill i Plaica (HS 215 m). Jumps over 240 m ca be realized o this hill; the flyig time ca be over 7 secods; the flyig velocity ca be betwee 100 km/h ad 115 km/h. The variability of legth of the jumps o the biggest jumpig hill is always much bigger tha o ormal jumpig hills. This is a opportuity to discover some importat differeces betwee the best ad the less successful ski jumpers with regard to the chose kiematic parameters of the ski jumpig techique. The variability of legth of the jumps is represeted by differeces i the flyig curve. The differeces i the flyig curves are sigificat o the bigger jumpig hills. The kiematic characteristics of the flyig curve are cosequeces of may kietic factors of the iertial force eviromet (Vaverka, 1987). For experts ad researchers of ski jumpig, aalysis of the top-level performers ski-jumpig techique is the most frequetly used solutio i the process of fidig optimal techique allowig the ski jumpers to accomplish their best competitive performace. Some of these research studies were more focused o the study of the i-ru, push-off ad early flight phase techiques (Virmavirta & Komi, 1994; Ardt, Brügema, Virmavirta, & Komi, 1995; Komi & Virmavirta, 1997; Vaverka, Jaura, Elfmark, & Saliger, 1997; Jošt, Čoh, Pustovrh, & Ulaga, 1999; Sasaki, Tsuoda, & Hoshio, 2001; Virmavirta, Kiveskas, & Komi, 2001; Joo-Ho Sog, Youg-Ji oo, & Youg-Hoo Kwo, 2004; Ettema, Brate, & Bobbert, 2005). Some research studies were more focused o the study of the flight techique (Wataabe & Wataabe, 1993; Jošt, 1994; Hiroshi, Shusuke, Tadaharu, Hirotoshi, & Kazutoshi, 1995; Jošt, Kugovik, Strojik, & Colja, 1997; Jošt, Vaverka, Kugovik, & Čoh, 1998; Schmölzer & üller, 2002; Seo, urakami, & Yishida, 2004a; Seo, Wataabe, & urakami, 2004b; Schmölzer, & üller, 2005; Virmavirta, Isolehto, Komi, Brüggema, üller, & Schwameder, 2005). 74

2 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 The first goal of the curret study was to aalyse the relatio betwee i-ru ad take-off velocity, ad the legth of flyig. The hypothesis was set that the group of best ski jumpers would have a sigificatly higher i-ru velocity tha the group of less successful oes. The i-ru velocity ad take-off velocity ifluece directly both the horizotal ad vertical velocity i the first part of the flight. Performace of a ski jumper, from the aerodyamic factor aspect, first depeds o the optimizatio of the push-off factors i the take- -off phase (Virmavirta & Komi, 1994; Komi & Virmavirta, 1997). This meas that take-off factors (vertical push-off acceleratio, rotatio, accuracy of the push-off ad the activity of the arms) are aerodyamic efficiecy causal factors durig the take-off phase (Vaverka, et al., 1997). I the first part of the flyig phase, the ski jumper has to assume the optimal aerodyamic positio for flyig. This will maximize the horizotal velocity ad miimize the vertical velocity of flyig. From this perspective, it could be expected that the best group of ski jumpers would have a higher flyig curve tha the group of less successful oes ad a better aerodyamic positio after the take-off. The flight phase represets a costituet part of the ski jumpig techique, which sigificatly determies the legth of the ski jump (Sasaki, et al., 2001; Schmölzer & üller, 2002, 2005; Seo, et al., 2004). Further, the optimal techique activity of the ski jumper i the flight phase is extremely importat. The first parameter that determies the ski-flyig techique is the height of the flyig curve. The group of least successful ski jumpers has a lower height of flyig curve tha the best group. The secod parameter of the flyig techique is the optimal aerodyamic positio. The best ski jumpers are supposed to have a better aerodyamic positio tha the less successful oes. At the begiig of flyig, the jumper has to solve two idepedet tasks of special ski jumpig techique. The first oe is to reach the optimal height of flyig ad the secod oe is to assume ad maitai the optimal aerodyamic positio (Schmolzer & üller, 2005; Ardt, et al., 1995; Jošt, et al., 1998; Jošt, et al., 1999; Virmavirta, et.al., 2005). The combiatio of both parameters is crucial to the best ski jumpig techique (Virmavirta, et al., 2005). The height of flyig i the begiig of the flight first depeds o the take-off force impulse o the take- -off table (Virmavirta & Komi, 1994). Oe part of this take-off force is eeded to reach the optimal aerodyamic positio ad oe part to attai the higher curve of flyig i the first part of flyig. From the aerodyamic aspect of the ski jumpig flyig techique, the optimal aerodyamic forces (drag ad lift force) must be preset durig the flight phase (Sasaki, et al., 2001). The maximizatio of lift force has a positive effect o miimizig the egative effect of drag force. I previous research, the most sigificat correlatio with the legth of the jump was foud i the agle betwee the body ad skis, ad the ski agle of attack at the ed of the first phase of the flight (Jošt, et al., 1998; Virmavirta, et al., 2004). Drag force, actig egatively i the horizotal plae of flyig, has to be miimal throughout the flight phase. For this reaso, a special aerodyamic idex was developed as the vertical distace betwee the highest poit o the body ski jumpers ad the to-the-earest poit of the skis. This idex would be i a sigificat egative correlatio with the legth of the jump. The best group of ski jumpers should have miimal values, ad the below-average group of ski jumpers should have maximal values of the aerodyamic idex. Oe of the goals of this research was to discover the correlatio, if ay, betwee the legth of the jumps ad the out-ru velocity measured at the space distaces from 245 m to 255 m. Namely, it could be hypothetically expected that the least successful group of ski jumpers had a higher out- -ru velocity tha the best group. ethods I this research, the ski jumpers participatig i three competitive rouds of the 2009 World Cup i Ski Flights at Plaica (HS 215 m) were aalysed. O the first day (Friday, 20 th arch, 2009), 40 jumpers competed i oly oe roud (30 jumpers were aalysed). I the secod competitio day (Suday, 22 d arch, 2009), 34 jumpers competed i the first ad 30 jumpers i the fial roud. The ski jumpers were divided ito three quality groups (Best, Average, Below Average) accordig to the jump legth i a particular roud. Values of the variables (legth of the jumps i metres); time of flyig i secods; i-ru velocity expressed i km/h, measured accordig to the FIS rules at a distace of 8 m, that is, m before the take-off bridge; take-off velocity i km/h, measured for the last 10 m o the take-off table; out-ru velocity i km/h, measured at the distace betwee the 245 th m ad 255 th m) were obtaied from the official records of the Competitio Office. The variables of i-ru, take-off ad out-ru velocity were measured with photocells placed.2 m above the sow profile. The kiematic variables ski-flyig techique movemet, the aerodyamic idex of flyig ad the height of the flyig curve were measured by meas of a 2-D video aalysis. The weather coditios were excellet durig recordig, with perfect visibility. The recordig was carried out with video cameras with a frequecy of 50 frames per secod. The first camera recorded flyig betwee the 10 th ad 25 th m, the secod camera recorded flyig betwee the 60 th ad 80 th m, ad the third camera recorded flyig betwee the 110 th ad 130 th m. Digitalizatio of the selected frames at the 17 th m, 75 th m ad 120 th m was carried out maually. The flight positio of 75

3 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 idividual athletes was recorded at a average height level of the flyig curve. Distaces betwee the ski jumper ad cameras depeded o the give terrai (betwee 12.5 m ad 80 m). For the calibratio of the space dimesios at a chose poit of flyig, a specially made cross-shaped marker was used. I Figure 1, the method of space calibratio at the poit 120 m after the take-off bridge is preseted. The sigificace of the correlatio betwee the variable legth of the jump ad the measured variables was established by usig Pearso correlatio coefficiet (r) for all the subjects i each competitive roud. The statistical data were computed for each group separately ad reported as meas ad stadard deviatios (, ). To establish statistical sigificace of the differeces betwee Height of flyig Aerodyamic idex Figure 1. Calibratio of the space durig a flyig phase with the specially cross-measured procedure for takig the data of the variables height of flyig ad aerodyamic idex at 120 m. The 2D model of a jumper s body ad skis cosisted of a three-segmet model with three referece poits. The first poit o the body, the trochater major poit, was used to measure the variable height of flyig (vertical distace betwee the sow profile of the jumpig hill ad the body poit trochater major). The secod poit was determied as the top of the head or the highest poit of the body durig the flyig phase i the chose referece space poit. The third poit was determied as the earest vertical poit of the ski positio. The last two poits were used to measure the variable aerodyamic idex (see Figure 1). The aerodyamic idex is the maximum vertical distace betwee the highest poit of the ski jumper s body ad to the groud earest poit o the skis. The miimal values of that idex idicate a better aerodyamic efficiecy of flyig. the groups, a oe-way sigle-factor aalysis of variace (ANOVA) was used. The criterio of statistical sigificace was accepted with a 5% twosided alpha error i both statistical methods. Results The differeces betwee the defied quality groups of ski jumpers i the variables of the jump legth ad the time of flyig were statistically sigificat (F prob. =.01). The maximal differeces (45.7 m) existed i the first roud of the secod competitio o Suday (Table 1). I Table 2 the statistical results of the i-ru, take-off ad out-ru velocity are show. The correlatio coefficiets betwee the legth of the jumps ad variables height of flyig at the poit of 75 m ad 120 m were statistically sigificat (Table 3). 76

4 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 Table 1. Aalysis of variace for the depedet variables: legth of the jump ad time of flyig (s) Name of the group BEST AVERAGE BELOW AVERAGE F prob. Competitive rouds Legth of the jump Friday 1 st roud ** Suday 1 st roud ** Suday 2 d roud ** Time of flyig (s) r Friday 1 st roud *.96** Suday 1 st roud *.98** Suday 2 d roud *.95** Table 2. Results of aalysis of variace ad correlatio of the idepedet variables of velocity Name of the group BEST AVERAGE BELOW AVERAGE F prob. r Competitive rouds I-ru velocity accordig to FIS (km/h) Friday 1 st roud Suday 1 st roud Suday 2 d roud * I-ru velocity o the take-off table (km/h) Friday 1 st roud Suday 1 st roud * Suday 2 d roud Out-ru velocity (km/h) Friday 1 st roud * Suday 1 st roud Suday 2 d roud Table 3. Results of aalysis of variace ad correlatio of depedet variables: height of flyig at differet poits of jumpig hill Name of the group BEST AVERAGE BELOW AVERAGE F prob. r Competitive rouds Height of flyig 17m after the take-off edge Friday 1 st roud Suday 1 st roud Suday 2 d roud Height of flyig 70m after the take-off edge Friday 1 st roud *.59** Suday 1 st roud ** Suday 2 d roud *.58** Height of flyig 120m after the take-off edge Friday 1 st roud *.74** Suday 1 st roud *.79** Suday 2 d roud *.73** 77

5 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 Table 4. Results of aalysis of variace ad correlatio of idepedet variables: idex of aerodyamic efficiecy of flyig at differet poits of the jumpig hill Name of the group BEST AVERAGE BELOW AVERAGE F prob. r Competitive rouds Idex of aerodyamic efficiecy of flyig 17 m after the take-off edge Friday 1 st roud Suday 1 st roud Suday 2 d roud Idex of aerodyamic efficiecy of flyig 70 m after the take-off edge Friday 1 st roud Suday 1 st roud * -.73** Suday 2 d roud Idex of aerodyamic efficiecy of flyig 120 m after the take-off edge Friday 1 st roud Suday 1 st roud * -.56** Suday 2 d roud * -.40** Leged: umber of jumpers i selected group, arithmetic mea of the group; stadard deviatio withi the group; F prob. sigificace of the F-test, r Pearso correlatio coefficiet with the variable legth of the jump, (*) asterisk deotes statistically sigificat differeces betwee the quality groups of the ski jumpers (*p<.05; **p<.01). The variables of the aerodyamic idex were strogly correlated to the legth of the jumps i the middle of flyig at 120 m at the secod Suday competitio (Table 4). Discussio ad coclusios The variability of the defied quality groups of ski jumpers from the aspect of the jump legth ad time of flyig was large ad statistically sigificat i all three rouds (F prob. =.01). The jumpig distaces were, o average, much loger at the Suday competitio tha o Friday whe the jumpers performed i poor widy coditios (Table 1). The jumpers eeded more jumps o the biggest flyig jumpig hill to adjust their optimal flyig techique, which also ecouraged a more competitive performace with greater distaces. Geerally, the i-ru, take-off ad out-ru velocities were ot sigificatly correlated to the legth of the jumps ad did ot differetiate amog qualitative groups i a statistically sigificat maer (Table 2). Yet, some sigificat correlatios were established (p=.05), but oly for oe competitive roud. The average i-ru velocity was a little higher tha the velocity o the take-off table. The out-ru velocity was by approximately 6 to 10% higher tha the i-ru velocity. Durig the first competitio roud, the out-ru velocity was much higher tha the oes i the secod ad third competitio rouds. O Friday afteroo, durig the first roud, wid coditios were ot as good as i the secod ad third competitio rouds o Suday morig. The out-ru velocity was strogly iflueced by wid coditios. With good wid coditios, the lift force icreased ad the flyig velocity decreased ad, cosequetly, so did the out-ru velocity (Schmölzer & üller, 2002). Accordig to the fidigs of this study, the developmet of a ew, bigger flyig hill could be easier whe cosiderig the flyig curve. The variable the height of flyig attaied geerally the miimum value at the 17 m poit after the take-off edge i all groups of ski jumpers (Table 3). The group of best ski jumpers had, o average, the biggest values i all rouds. The differeces betwee the best group ad the below average group were statistically sigificat i all three jumps at the poits of 75 m ad 120 m after the take-off table. This differece had mostly already arise at the flyig poit of 70 m. The height of flyig at the poit of 17 m did ot sigificatly differetiate amog three qualitative groups of ski jumpers. The differeces i the height of flyig betwee the average value of the best, average ad below average group were statistically sigificat at the 70 m poit ad especially at the 120 m poit i all three competitive rouds. The statistical sigificace icreased up to the distace of 120 m ad beyod; this differetiated the best from the below-average ski jumpers to a great extet (F prob. =.01). Sports success of ski jumpers depeds especially o the aspect of the aerodyamic positio of the system body ad ski. Bigger differeces were expected i the variable aerodyamic idex of flyig. After the take-off (17 m), there were o differeces betwee the defied groups of ski 78

6 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 jumpers (Table 4). The first statistically sigificat differeces occured i the first roud after the 75 m poit i the Suday competitio. I the middle of flyig (at the 120 th m), importat differeces were established betwee the qualitative groups i the Suday competitio i both rouds (F prob. =.01). The aerodyamic idex, which idicates the ability of a ski jumper to assume ad maitai the optimal aerodyamic positio i the cetral phase of flyig, was a statistically sigificat factor for differetiatig betwee the groups of ski jumpers at the 70 m poit ad, especially, at the 120 m after leavig the edge of the take-off platform. The ski jumpers of the best group had a better aerodyamic positio i the middle of the flight phase the their rivals. I accordace with fidigs of previous studies ad the theory of the techique of the movemet of a ski jumper i the mai flight phase (Vaverka, 1987), the jumper must, at each poit of the flight, assume such a positio that will maximize the horizotal velocity while simultaeously miimizig the vertical velocity of the body s cetre of gravity movemet. It could be said that ski jumpers developed a good ski-flyig positio at each time of flyig from the begiig to the ed. The best group of ski jumpers was more successful i doig so tha the below-average group. I some studies, this positio was statistically sigificat ad the most importat factor for distiguishig betwee the best ad the below-average groups of ski jumpers (Jošt, et al., 1997; Jošt, et al., 1998; Jošt, et al., 1999; Schmölzer & üller, 2005; Virmavirta, et al., 2005). O the basis of the results obtaied i this research, the followig coclusios ca be draw: - The variability of the defied quality groups of ski jumpers from the aspects of the jump legth ad the time of flyig was large ad statistically sigificat (F prob. =.01). - The i-ru velocity showed a positive tred i the discrimiatio of quality groups of ski jumpers, especially sigificatly durig the Suday competitio i the secod roud (r=.31, sig r=.05). - At the poit of 75 m ad, especially, of 120 m after the edge of the take-off platform, the best group of ski jumpers had the biggest height of flyig. The differeces i the vertical height of flyig cofirmed a tedecy towards positive correlatios betwee this variable ad the jump legth (r mi =.42, r max =.79). The best ski jumpers group attaied a statistically sigificat bigger vertical height of flyig i all three competitive rouds at the poits of 75 m (F prob. =.01/.05/.10) ad 120 m (F prob. =.01). - After the take-off phase, the best group of ski jumpers showed tedecies to reach the optimal aerodyamic positio i the flight phase (especially importat i the middle of flyig). - The velocity of flyig durig the total phase of flyig icreased costatly. The out-ru velocity was about 6 10% higher tha the i-ru velocity. - The out-ru velocity i the shortest jumps was ot sigificatly faster tha i the logest jumps. Due to bad weather coditios i the first competitio roud o Friday, whe the startig gate was fairly low, the height of startig gate was icreased o Suday, which also icreased out-ru velocity. I the Suday 2 d roud, a sigificat correlatio (r=-.35, sig r=.05) was established betwee the legth of the jump ad out-ru velocity. Refereces Ardt, A., Brügema, G.P., Virmavirta,., & Komi P. (1995). Techiques used by Olympic ski jumpers i the trasitio from take-off to early flight. Joural of Applied Biomechaics, 11(2), Ettema, J.C., Brate, S., & Bobbert, F.. (2005). Dyamics of the i-ru i ski jumpig: A simulatio study. Joural of Applied Biomechaics, 21(3), Hiroshi, J., Shusuke, S., Tadaharu, W., Hirotoshi, K., & Kazutoshi, K. (1995). Desirable glidig styles ad techiques i ski jumpig. Joural of Applied Biomechaics, 11(4), Jaura,., Vaverka, F., & Elfmark,. (1995). A compariso betwee the kiematic characteristics of the trasitio phase of ski jumpig o jumpig hills with differet critical poits. I T. Bauer (Ed.), Proceedigs of the 13 th Iteratioal Symposium o Biomechaics i Sport (pp ). Thuder Bay: Lakehead Uiversity. Joo-Ho Sog, Youg-Ji oo, & Youg-Hoo Kwo (2004). A comparative study of the take-off ad early-flight phases i ski jumpig. Iteratioal Joural of Applied Sport Scieces, 16(2), Jošt, B. (1994). Differeces i some kiematic flight parameters betwee the classical ad the ew so-called V techique i ski jumpig. Kiesiology, 26(1-2), Jošt, B., Kugovik, O., Strojik, V., & Colja, I. (1997). Aalysis of kiematic variables ad their relatio to the performace of ski jumpers at the World Champioship i Ski Flight at Plaica i Kiesiology, 29(1), Jošt, B., Vaverka, F., Kugovik, O., & Čoh,. (1998). Differeces i selected kiematic flight parameters of the most ad the least successful ski jumpers of the 1996 World Cup competitio i Isbruck. Biology of Sport, 15(4),

7 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 Jošt, B., Čoh,., Pustovrh, J., & Ulaga,. (1999). Aalysis of the selected kiematic variables of the take-off i ski jumps i the fials of the World Cup at Plaica i Kiesiologia Sloveica, 5(1-2), Komi, P.V., & Virmavirta,. (1997). Ski-jumpig take-off performace: Determiig factors ad methodological advaces. I E. üller, H. Schwameder, E. Korexl & C. Rascher (Eds.), Proceedigs book of the First Iteratioal Cogress o Skiig ad Sciece, St. Chrisoph a. Arlberg, Austria (pp. 3-26). Lodo [etc.]: E & FN Spo. Sasaki, T., Tsuoda, K., & Hoshio, H. (2001). Aalysis of aerodyamic force o ski jumpers durig the iitial flight phase usig mathematical model. I E. üller, et al. (Eds.), Sciece ad Skiig II, Proceedigs book of the Secod Iteratioal Cogress o Skiig ad Sciece, St. Chrisoph a. Arlberg, Austria (pp ). Hamburg: Kovač. Schmölzer, B., & üller, W. (2002). The importace of beig light: Aerodyamic forces ad weight i ski jumpig. Joural of Biomechaics, 35(8), Schmölzer, B., & üller, W. (2005). Idividual flight styles i ski jumpig: Results obtaied durig Olympic Games competitios. Joural of Biomechaics, 38(5), Seo, K., urakami,., & Yoshida, K. (2004a). Optimal flight techique for V-style ski jumpig. Sports Egieerig, 7(2), Seo, K., Wataabe, I., & urakami,. (2004b). Aerodyamic force data for a V-style ski jumpig flight. Sports Egieerig, 7(1), Vaverka, F. (1987). Biomechaics i ski-jumpig. Olomouc: Uiverzita Palackého. Vaverka, F., Jaura,., Elfmark,., & Saliger, J. (1997). Iter- ad itra-idividual variability of the ski jumpers takeoff. I E. üller, H. Schwameder, E. Korexl & C. Rascher (Eds.), Proceedigs book of the First Iteratioal Cogress o Skiig ad Sciece, St. Chrisoph a. Arlberg, Austria (pp ). Lodo [etc.]: E & FN Spo. Virmavirta,., & Komi, P.V. (1994). Take-off aalysis of a champio ski jumper. Coachig ad Sport Sciece Joural, 1(1), Virmavirta,., Kiveskas, J., & Komi, P.V. (2001). Take-off aerodyamics i ski jumpig. Joural of Biomechaics, 34(4), Virmavirta,., Isolehto, J., Komi, P.V., Brüggema, G.P., üller, E., & Schwameder, H. (2005). Characteristics of the early flight phase i the Olympic ski jumpig competitio. Joural of Biomechaics, 38(11), Wataabe, K., & Wataabe, I. (1993). Aerodyamics of ski jumpig-effect of V-style to distace. I Proceedigs of the Iteratioal Society of Biomechaics XIV th Cogress (pp ). Paris: Iteratioal Society of Biomechaics. Submitted: April 28, 2010 Accepted: ay 2, 2011 Correspodece to: Jaez Vodičar, aged Faculty of Sport, Uiversity of Ljubljaa Gortaova 22, 1000 Ljubljaa Fax: Phoe: jaez.vodicar@fsp.ui-lj.si 80

8 Vodičar, J. ad Jošt, B.: THE RELATIONSHIP BETWEEN SELECTED KINEATIC... Kiesiology 43(2011) 1:74-81 POVEZANOST IZABRANIH KINEATIČKIH PARAETARA I DULJINE SKOKOVA NA NATJECANJU U SKIJAŠKI LETOVIA Cilj je ovoga istraživaja bio aalizirati izabrae kiematičke parametre (vrijeme leta, brziu a skakaoici, brziu odraza, brziu leta, visiu leta a 17. metru leta, visiu leta a 75. metru leta, visiu leta a 120. metru leta, aerodiamički ideks a 17. metru leta, aerodiamički ideks a 75. metru leta te aerodiamički ideks a 120. metru leta) ajboljih svjetskih skijaša letača koji su sudjelovali a dva fiala atjecaja Svjetskoga kupa u skijaškim letovima (petak i edjelja) a Plaici (visia skakaoice 215 m), Sloveija, godie. Svi skokovi bilježili su se trima kamerama, 50 slika u sekudi, a letači su bili simai tijekom počete faze leta (17 metara od odrazoga ruba skakaoice) te u središjem dijelu skoka (75 metara od odrazoga ruba skakaoice i 120 metara od odrazoga ruba skakaoice). Skijaši su bili podijeljei u tri statistički začajo različite kvalitete grupe, određee prema duljiama skokova u sve tri skakačke serije (F prob. =0,01). Korelacijskom aalizom i uivarijatom aalizom varijace utvrđea je statistička začajost majega broja korelacija među defiiraim kiematičkim varijablama i duljie skoka. Razlike u vertikaloj visii leta potvrdile su tedeciju prema pozitivim korelacijama između avedee varijable i duljie skoka (r mi =0,42, r max =0,79). Skupia ajboljih skijaša letača postigla je i statistički začajo višu vertikalu visiu krivulje leta u sve tri serije letova u točki 75 metara od odrazoga ruba skakaoice (F prob bila je između 0,00 i 0,08) i u točki 120 metra od odrazoga ruba skakaoice (F prob. =0,01). Najbolja grupa skijaša letača imala je bolju aerodiamičku poziciju tijekom faze leta, osobito u točki 75 metara od odrazoga ruba skakaoice (prva serija u edjelju, r =-0,73; p =0,00) i u točki od 120 metara od odrazoga ruba skakaoice (obje skakačke serije u edjelju, F prob. =0,01). Ključe riječi: skijaški skokovi, kiematička aaliza leta, fiale Svjetskoga kupa u skijaškim letovima 2009, Plaica visia skakaoice 215 metara 81