Vilas-Boas, Machado, Kim, Veloso (eds.) Portuguese Journal of Sport Sciences Biomechanics in Sports 29 11 (Suppl. 2), 2011 higher velocity can be gained in the . Moreover, GRF explained a percentage of the KINEMATICAL ANALYSIS OF FIVE DIFFERENT IN execution time but not the reaction time or the total response time; it seems that when mechanical analyses in taekwondo are done, the kick should be divided in several periods Coral Falco1, Isaac Estevan1 and Manfred Vieten2 because it offers important information. Execution and different phases of the kick performance should be analyzed in-depth in future studies. Catholic University of Valencia, Valencia, Spain1 Although the roundhouse is the most frequent kick in taekwondo combats, it is also a University of Konstanz, Konstanz, Germany2 complex and explosive motor task (Estevan et al., in press). In line with Fortier et al. (2005), our results showed that the kick start is characterized by large forces and by the ability to The purpose of this study was to identify those foot techniques in taekwondo to the head generate these forces in a short period of time. Thus, the results showed that independently with the highest potential for success in competition. We compared five of the most of the stance position, taekwondo athletes can react in the same time and can also obtain frequently used kicks, the round kick, front leg axe kick, clench axe kick, jump spin back the same peak velocity in the kick. From the 0º and 45º positions athletes kick in less time kick and jump spin hook kick. Since the right timing and fast movements vastly determine compared to the 90º position, and at the 45º and 90º positions a higher GRF means less success, we looked at the reaction time, execution time and total response time. Eight execution time, but no relation was found at the 0º position. Thus, it seems that the 45º high level athletes participated in the study. Three Casio HD cameras operated on 300 stance position could enhance sport performance. This could also have important Hz were used to record kinematics parameters. A Hybrid II Crash Dummy head (H2D) implications from a tactical perspective. The 45º position allows athletes to do whichever and neck were instrumented. The one-way ANOVA showed that there were no technique they prefer, even back kicks. Also, this position enables the athletes to perform differences in reaction time while there were differences in the execution time and, as a attack or counterattack kicks, which may be due to a better trunk orientation and means consequence, in the total time (p < .01) as well. more adequate options to generate forces in the direction the athletes desire. However, KEY WORDS: , performance, reaction time, execution time, total time future studies should analyze the mechanical performance of different types of kicks and in different contexts, such as attack or counterattack kicks in taekwondo. In addition, due to the INTRODUCTION: Taekwondo is a full contact combat sport wherein the competitors win small number of participants, the results of our study can not be generalized to the whole points by hitting the opponents’ chest gear or the head. In 2009, World Taekwondo population. More studies with a higher number of athletes are needed before a conclusion Federation competition rules changed and kicking the head scores three points (2 before) can be drawn on the possible effect the stance position may have on kick performance. while a kick to the chest just scores one. Even before the rule change athletes preferred to kick to the opponents’ head due to its higher scoring value or sudden win by knock out (Koh CONCLUSION: This report presents novel scientific information in taekwondo. The stance et al., 2004). Therefore, training programs and game strategy often focus on attacking the position is a factor that affects the mechanical performance of taekwondo athletes’ kicks. The opponents head. Scientific literature (Serina & Lieu, 1991; Sorensen et al., 1996) categorizes 90º stance position involves longer execution and total time than the 0º and 45º stance two principally different kicking mechanisms to reach the opponent. The swing kicks are positions in the roundhouse kick. The 0º and 45º stance positions seem more appropiate kicks performed with body rotation directed to the side of the opponent, and the thrust kicks, than the 90º stance position. which attempt to hit the front in a straight movement. Research on kicks to the chest (Serina & Lieu, 1991) has determined that swing kicks are faster than thrust kicks, with the REFERENCES: roundhouse kick being identified as the fastest kicking technique of all (Pieter & Pieter, nd Cohen, J. (1988). Statistical power analysis for the behavioural sciences (2 ed.). Hillsdale, NJ: 1995). Lawrence Erlbaum. There is a lack of research for kicks to the head level. Little is known about what makes one Estevan, I., Álvarez, O., Falco, C., Molina-García, J. & Castillo, I. (in press). Impact force and time technique more efficient than the other. The round kick (Estevan et al., 2009) takes analysis influenced by execution distance in a roundhouse kick to the head in Taekwondo. Journal of 0.286±0.100 seconds to be performed, the front leg axe kick (Tsai et al., 2005) takes Strength and Conditioning Research. 0.327±0.026 seconds, and the jump spin hook kick (Tsai et al., 2007) takes 0.270±0.029 Falco, C., Alvarez, O., Castillo, I., Estevan, I., Martos, J., Mugarra, F. & Iradi, A. (2009). Influence of seconds. Of all head techniques successful in scoring, five kicks are dominating combats the distance in a roundhouse kick’s execution time and impact force in Taekwondo. Journal of (Koh et al., 2004): the straight axe kick or front leg axe kick, the outside in axe kick or clench Biomechanics, 42, 242-248. axe kick, the roundhouse kick to the head, the jumping spinning kick or jumping spinning Fortier, S., Basset, F.A., Mbourou, G.A., Favérial, J. & Teasdale, N. (2005). Starting block hook kick, and the jumping back kick or jumping back kick. Therefore, it is necessary to study performance in sprinters: a statistical method for identifying discriminative parameters of the them with regard to reaction time and execution time. Execution time appears to be one of performance and an analysis of the effect of providing feedback over a 6-week period. Journal of the key elements for victory (Vieten et al., 2007). Therefore, we identify a potentially Sports Science and Medicine, 4, 134-143. successful kicking technique by its short total time, the sum of reaction and execution time. Kim, J.W., Kwon, M.S., Yenuga, S.S. & Kwon, Y.H. (2010). The effects of target distance on pivot hip, trunk, pelvis, and kicking leg kinematics in Taekwondo round house kick. Sports Biomechanics, 9, 98- METHODS: Participants: Eight male Taekwondo athletes from the Spanish National 114. Taekwondo team participated in this study. Their mean heights, weights and ages were Wang, N. & Liu, Y.H. (2002). The effect of stance on attack-time: part II – reverse punch. In 1.77±0.07 m, 68.80±3.01 kg and 20.40±2.05 years. Informed consent was obtained from K.E. Gianikellis (Ed.), Proceedings of the 20th International Symposium on Biomechanics in Sports (pp each subject prior to the study. 214-218). Cáceres, Spain. Experimental design and instruments: Each subjects’ foot was marked with reflective markers at the first and second metatarsals. Each participant’s preferred target distance was Acknowledgement used as the execution distance (Kim et al., 2010). Five different head kicks were performed We would like to thank Professor Joseph Hamill because of his help in the data acquisition process. five times in random order; round kick, front leg axe kick, clench axe kick, jump spin back This research was supported by the SGS grant of University of Ostrava (No. 6109). kick and jump spin hook kick. A kicking action was initiated by switching on the LED on the chest height of the test dummy, this also started the clock time. The variables of this study

ISBS 2011 219 Porto, Portugal Vilas-Boas, Machado, Kim, Veloso (eds.) Portuguese Journal of Sport Sciences Biomechanics in Sports 29 11 (Suppl. 2), 2011 were: reaction time (as the time period from LED switched on until the athlete performed the spin back kick, the jump spin hook kick, the front leg axe kick and the clench axe kick. We first movement with the foot), execution time (as the period of time from the first movement emphasize there were no statistically significant execution time differences between the with the kicking foot until the foot impacted the head of the test dummy), and total time (as round and the jump spin back kick, as well as between the jump spin back kick and to the the sum of reaction time and execution time). Three Casio HD cameras (300 Hz) were used jump spin hook kick. Our study shows that execution time can explain the kicking and scoring for recording. A Hybrid II Crash Dummy head (H2D) and neck were instrumented. The H2D rate found by previous studies (round-kick, back-kick, axe-kick, back round-kick and front- was fixed to a height adjustable frame and fitted with a protective TKD helmet (LeCAF - kick) (Chian, 1991; Lee, 1992; Tsia et al., 1998; cited by Lan et al., 2000). The only exception Seoul, South Korea). is the axe-kick that our taekwondo players performed making a previous back-step which Statistical analysis: One way ANOVA was used to compare mechanical variables among increased the execution time. the five kicks. Pairwise comparisons were performed using Bonferroni statistics to analyze In line with Pieter and Pieter (1995), the round kick was the fastest kick among both the significant effects of ANOVAs. Cohen’s d score was used to analyze the effect size. Cohen swing and thrust kicks. It might be the reason why the round kick is the most often used considered that a d larger than 0.8 signified a large effect. The level of significance was set technique in training and competition. It is necessary to identify if the round kick has an to 0.05. intrinsic mechanism that makes it faster than other techniques. Or, is it due to a more frequent use, both during training and competition and therefore athletes being more RESULTS: Statistical descriptions (mean and standard deviation) are shown in Table 1. The experienced in performing this technique? Since the jump spin back kick has a spin prior to one-way ANOVA showed that there were no differences in reaction time (p = .28) while there the kick, we can not describe it either as swing or as a thrust kick. It is needed to study this were differences in execution time (p < .01) and in total time (p < .01). The clench axe kick technique further in order to know the purpose of this initial movement. In agreement with had the highest execution time, followed by the front leg axe kick and the jump spin hook Lan et al. (2000), we did not find differences in execution time when comparing the round kick, while there were no differences between the jump spin back kick and the round kick. kick and the jump spin back kick. In this sense, we do not find a plausible explanation for the Lastly, the clench axe kick had the highest total time followed by the front leg axe kick which less utilization of this technique during a competition (Kohn et al., 2004). were also slower than the round kick. No differences were found between the round kick, the The results also showed that the clench axe kick had the highest execution time. Moreover, jump spin back kick or jump spin hook kick in total time. All effect sizes were above 0.8. this technique also had the highest total time followed by the front leg axe kick. It can be Table 1 related with the back-step performed by the athletes, previous to the kicking movement. Comparative analysis among five different kicks in time variables. Interestingly, the axe kick causes the second highest concussion rate (Koh et al., 2004). It round kick front leg axe clench axe kick jump spin jump spin hook seems that if the taekwondo player has a lot of time to perform a technique, he/she can kick back kick kick adjust it to an optimal performance and thereby optimize the energy exchange. No Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD differences have been found when comparing the round kick, the jump spin back kick and reaction 0.281±0.061 0.264 ± 0.076 0.272 ± 0.102 0.299 ± 0.065 0.274 ± 0.055 the jump spin hook kick. Those techniques with a previous spin are mainly used during a time [s] counter attack. More research is needed to focus on the intrinsic mechanisms of these execution abc adfg befh gh cde 0.460±0.095 0.608 ± 0.100 0.839 ± 0.121 0.509 ± 0.063 0.540 ± 0.081 techniques. The analysis might uncover the reasons that motivate the athletes to perform time [s] those techniques in each specific situation during competition. Lastly, future studies should total time ab ac bcde d e 0.740±0.086 0.872 ± 0.088 1.119 ± 0.122 0.808 ± 0.092 0.809 ± 0.186 [s] attempt to find out what happens between the first movement till the foot leaves the floor, and Note: Similar letters to the right of the mean and SD value mean significant differences (p < 0.05). between the time the foot leaves the floor and hitting the target (Lan et al., 2000; Estevan et al., 2009). Studying those time variables will give a better understanding of the use of these DISCUSSION: In taekwondo, fast reactions are essential for success in competitions (Vieten techniques during competition. One limitation of the study is that we tested one weight et al., 2007). The quicker the athletes react, the more time they have to accomplish their category of taekwondo athletes only. In this sense, it will be important to apply the same strategy (Tsai et al., 2004). Therefore, taekwondo athletes should not only use those research to other weight categories as well as to female athletes. techniques that allow them to react fast but also the techniques where they need least time to reach the opponent (Estevan et al., 2009). However, to our knowledge the presented CONCLUSION: We did not find differences in reaction time among the five kicks. Hence, this study is the first to compare time variables for the techniques to the head most often used in phase within a combat's action does not select a technique to having a higher scoring competition (Koh et al., 2004). probability. Execution time however, is different between the kicks. Swing kicks (round kick, In spite of the fact, that athletes were instructed to perform kicks in pre-selected order, no jump spin back kick and jump spin hook kick) are faster than thrust kicks (clench axe kick significant differences in reaction time were observed. This indicates that the subjects mind and front leg axe kick). Interestingly, there are no statistically significant action time set does not influence their ability to react. Thus, it seems athletes are not in a specific differences comparing round kick and kicks with a previous spin. The new competition rules "mode" when prepared to perform a kick. However, our results are in contrast to Chou (1996, reward kicks initiated by a spinning motion with one additional point. The probability cited by Tsai et al., 2004) who studied four different kick actions and found that the axe-kick executing a successful technique (same action time) is alike for round kick and kicks with a and the round kick had lower reaction time than the other kicks. This might be due to the previous spin. Spin kicks do score higher, and consequently it is well advisable to use more differences in the definition of the reaction time variable. Therefore, future research should techniques with a prior spin during competition. study the time needed for the foot to leave the floor when comparing these techniques. In line with previous research (Serina & Lieu, 1991), the results of our study shown that REFERENCES: swing kicks (round kick and jump spin hook kick) were faster than thrust kicks (front leg axe Estevan, I., Falco, C., Alvarez, O., Mugarra, F., and Iradi, A. (2009). Mechanical comparison between kick and clench axe kick). Even the jump spin back kick can be considered a thrust kick, roundhouse to the chest and to the head in function of execution distance in taekwondo. In A.J. th there were no differences when comparing this kick with the swing kicks (round kick and Harrison, R. Anderson & I. Kenny (Eds.), Proceedings of the 27 International Conference on jump spin hook kick). It might be, as literature suggests, that the addition of the initial spin Biomechanics in Sports (pp. 596-599). Limerick, Ireland. prior to kick execution generates a greater kick velocity (Serina & Lieu, 1991). The sequence of kicks from short to longer execution time can be described as follows: round kick, the jump

ISBS 2011 220 Porto, Portugal Vilas-Boas, Machado, Kim, Veloso (eds.) Portuguese Journal of Sport Sciences Biomechanics in Sports 29 11 (Suppl. 2), 2011 were: reaction time (as the time period from LED switched on until the athlete performed the spin back kick, the jump spin hook kick, the front leg axe kick and the clench axe kick. We first movement with the foot), execution time (as the period of time from the first movement emphasize there were no statistically significant execution time differences between the with the kicking foot until the foot impacted the head of the test dummy), and total time (as round and the jump spin back kick, as well as between the jump spin back kick and to the the sum of reaction time and execution time). Three Casio HD cameras (300 Hz) were used jump spin hook kick. Our study shows that execution time can explain the kicking and scoring for recording. A Hybrid II Crash Dummy head (H2D) and neck were instrumented. The H2D rate found by previous studies (round-kick, back-kick, axe-kick, back round-kick and front- was fixed to a height adjustable frame and fitted with a protective TKD helmet (LeCAF - kick) (Chian, 1991; Lee, 1992; Tsia et al., 1998; cited by Lan et al., 2000). The only exception Seoul, South Korea). is the axe-kick that our taekwondo players performed making a previous back-step which Statistical analysis: One way ANOVA was used to compare mechanical variables among increased the execution time. the five kicks. Pairwise comparisons were performed using Bonferroni statistics to analyze In line with Pieter and Pieter (1995), the round kick was the fastest kick among both the significant effects of ANOVAs. Cohen’s d score was used to analyze the effect size. Cohen swing and thrust kicks. It might be the reason why the round kick is the most often used considered that a d larger than 0.8 signified a large effect. The level of significance was set technique in training and competition. It is necessary to identify if the round kick has an to 0.05. intrinsic mechanism that makes it faster than other techniques. Or, is it due to a more frequent use, both during training and competition and therefore athletes being more RESULTS: Statistical descriptions (mean and standard deviation) are shown in Table 1. The experienced in performing this technique? Since the jump spin back kick has a spin prior to one-way ANOVA showed that there were no differences in reaction time (p = .28) while there the kick, we can not describe it either as swing or as a thrust kick. It is needed to study this were differences in execution time (p < .01) and in total time (p < .01). The clench axe kick technique further in order to know the purpose of this initial movement. In agreement with had the highest execution time, followed by the front leg axe kick and the jump spin hook Lan et al. (2000), we did not find differences in execution time when comparing the round kick, while there were no differences between the jump spin back kick and the round kick. kick and the jump spin back kick. In this sense, we do not find a plausible explanation for the Lastly, the clench axe kick had the highest total time followed by the front leg axe kick which less utilization of this technique during a competition (Kohn et al., 2004). were also slower than the round kick. No differences were found between the round kick, the The results also showed that the clench axe kick had the highest execution time. Moreover, jump spin back kick or jump spin hook kick in total time. All effect sizes were above 0.8. this technique also had the highest total time followed by the front leg axe kick. It can be Table 1 related with the back-step performed by the athletes, previous to the kicking movement. Comparative analysis among five different kicks in time variables. Interestingly, the axe kick causes the second highest concussion rate (Koh et al., 2004). It round kick front leg axe clench axe kick jump spin jump spin hook seems that if the taekwondo player has a lot of time to perform a technique, he/she can kick back kick kick adjust it to an optimal performance and thereby optimize the energy exchange. No Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD differences have been found when comparing the round kick, the jump spin back kick and reaction 0.281±0.061 0.264 ± 0.076 0.272 ± 0.102 0.299 ± 0.065 0.274 ± 0.055 the jump spin hook kick. Those techniques with a previous spin are mainly used during a time [s] counter attack. More research is needed to focus on the intrinsic mechanisms of these execution abc adfg befh gh cde 0.460±0.095 0.608 ± 0.100 0.839 ± 0.121 0.509 ± 0.063 0.540 ± 0.081 techniques. The analysis might uncover the reasons that motivate the athletes to perform time [s] those techniques in each specific situation during competition. Lastly, future studies should total time ab ac bcde d e 0.740±0.086 0.872 ± 0.088 1.119 ± 0.122 0.808 ± 0.092 0.809 ± 0.186 [s] attempt to find out what happens between the first movement till the foot leaves the floor, and Note: Similar letters to the right of the mean and SD value mean significant differences (p < 0.05). between the time the foot leaves the floor and hitting the target (Lan et al., 2000; Estevan et al., 2009). Studying those time variables will give a better understanding of the use of these DISCUSSION: In taekwondo, fast reactions are essential for success in competitions (Vieten techniques during competition. One limitation of the study is that we tested one weight et al., 2007). The quicker the athletes react, the more time they have to accomplish their category of taekwondo athletes only. In this sense, it will be important to apply the same strategy (Tsai et al., 2004). Therefore, taekwondo athletes should not only use those research to other weight categories as well as to female athletes. techniques that allow them to react fast but also the techniques where they need least time to reach the opponent (Estevan et al., 2009). However, to our knowledge the presented CONCLUSION: We did not find differences in reaction time among the five kicks. Hence, this study is the first to compare time variables for the techniques to the head most often used in phase within a combat's action does not select a technique to having a higher scoring competition (Koh et al., 2004). probability. Execution time however, is different between the kicks. Swing kicks (round kick, In spite of the fact, that athletes were instructed to perform kicks in pre-selected order, no jump spin back kick and jump spin hook kick) are faster than thrust kicks (clench axe kick significant differences in reaction time were observed. This indicates that the subjects mind and front leg axe kick). Interestingly, there are no statistically significant action time set does not influence their ability to react. Thus, it seems athletes are not in a specific differences comparing round kick and kicks with a previous spin. The new competition rules "mode" when prepared to perform a kick. However, our results are in contrast to Chou (1996, reward kicks initiated by a spinning motion with one additional point. The probability cited by Tsai et al., 2004) who studied four different kick actions and found that the axe-kick executing a successful technique (same action time) is alike for round kick and kicks with a and the round kick had lower reaction time than the other kicks. This might be due to the previous spin. Spin kicks do score higher, and consequently it is well advisable to use more differences in the definition of the reaction time variable. Therefore, future research should techniques with a prior spin during competition. study the time needed for the foot to leave the floor when comparing these techniques. In line with previous research (Serina & Lieu, 1991), the results of our study shown that REFERENCES: swing kicks (round kick and jump spin hook kick) were faster than thrust kicks (front leg axe Estevan, I., Falco, C., Alvarez, O., Mugarra, F., and Iradi, A. (2009). Mechanical comparison between kick and clench axe kick). Even the jump spin back kick can be considered a thrust kick, roundhouse to the chest and to the head in function of execution distance in taekwondo. In A.J. th there were no differences when comparing this kick with the swing kicks (round kick and Harrison, R. Anderson & I. Kenny (Eds.), Proceedings of the 27 International Conference on jump spin hook kick). It might be, as literature suggests, that the addition of the initial spin Biomechanics in Sports (pp. 596-599). Limerick, Ireland. prior to kick execution generates a greater kick velocity (Serina & Lieu, 1991). The sequence of kicks from short to longer execution time can be described as follows: round kick, the jump

ISBS 2011 221 Porto, Portugal Vilas-Boas, Machado, Kim, Veloso (eds.) Portuguese Journal of Sport Sciences Biomechanics in Sports 29 11 (Suppl. 2), 2011

Kim, J.W., Kwon, M.S., Yenuga, S.S. & Kwon, Y.H. (2010). The effects of target distance on pivot hip, COMPARISON OF LUGERS’ START ELEMENTS ON A SLIDING TRACK AND AN trunk, pelvis, and kicking leg kinematics in Taekwondo round house kick. Sports Biomechanics, 9, 98- ICED START RAMP 114.

Koh, J.O., Watkinson, E.J. & Yoon, Y.L. (2004). Video analysis of head blows leading to concussion in 1 2 competition in Taekwondo. Brain Injury, 18 (12), 1287 – 1296. Veronika Fedotova and Viktor Pilipiv

Lan, Y.S., Wang, S.Y., Wang, L.L., Ko, Y.C. & Huang, C. (2000). The kinematic analysis of three th Institute of Biomaterials and Biomechanics, Riga Technical University, Riga, taekwondo kicking movements. In Y. Hong, D.P. Johns & R. Sanders (Eds.), Proceedings of the 18 1 International Symposioum on Biomechanics in Sports. Beijing, China. Latvia 2 Pieter, F., & Pieter, W. (1995). Speed and force in selected taekwondo techniques. Biology of sport, Sports Medicine Department, Latvian Olympic Team, Riga, Latvia 12 (4), 257-266. The aim of this study was to determine whether there are significant differences in timing Serina, E.R. & Lieu, D.K. (1991). Thoracic injury potential of basic competition Taekwondo kicks. of start elements that lugers perform on a sliding track and an iced start ramp built for Journal Biomechanics, 24(10), 951-960. training purposes. Male and female lugers with different competitive experience Sørensen, H., Zacho, M., Simonsen, E.B., Dyhre-Poulsen, P. & Klausen, K. (1996). Dynamics of the performed starts on the start ramp and on the luge track. Timing of start elements was martial arts high front kick, Journal of Sports Sciences, 14(6), 483 — 495. measured from high-speed video records and compared between start facilities. Most of Tsai, Y.J., Gu, G.H., Lee, C.J., Huang, C.F. & Tsai, C.L. (2005). The biomechanical analysis of the the athletes showed different timing of start phases at the track and the ramp. These taekwondo front-leg axe kick. Proceedings of the ISBS, Beiging, China (pp. 437- 440). differences partially arise from a necessity to assume a riding position in-time on the Tsai, Y.J., Lee, S.P. & Huang, C. (2004). The biomechanical analysis of taekwondo axe-kick in seniro track. Though training on the start ramp does not represent exactly start performance on high school athletic. In M. Lamontagne, D. Gordon, E. Roberson & H. Sveistrup (Eds.), Proceedings of a luge track, it is a convenient way for practicing technical elements of the start. the 22th International Symposioum on Biomechanics in Sports (pp. 453 – 456). Ottawa, Canada. KEY WORDS: timing analysis, high-speed video recording, start phases, winter sports. Tsai, Y.J., Huang, C.F. & Gu, G.H. (2007). The kinematic analysis of Spin-whip kick of taekwondo in elite athletes. Journal of Biomechanics, 40(S2), 780. The sport of luge is one of the fastest winter sports – athletes slide on iced Vieten, M., Scholz, M., Kilani, H. & Kohloeffel, M. (2007). Reaction time in Taekwondo. In H.J. Menzel INTRODUCTION: & M.H. Chagas (Eds.), Proceedings of the 25th International Symposium on Biomechanics in Sports tube-like tracks with speeds reaching values of 150 km/h, and thousandth of a second often (pp. 293-296). Ouro Preto: Brazil. determine a winner. It had been shown in previous research that a fast start time is a prerequisite for an excellent overall performance in the sport of luge (Bruggemann et al., Acknowledgement 1997); start records for each sliding track are even officially registered during major competitions. Athletes spend a lot of time mastering their start technique; the starts are We would like to thank the Spanish Taekwondo Federation for their co-operation and the participating taekwondo players for their help in the data acquisition process. This study has been partially practiced not only on the sliding tracks, but also at different other facilities, including specially supported by the Catholic University of Valencia (UCV 2011-007-001). constructed start ramps, both iced and for roller-sleds (Rogowsky & Wala, 1978). Although The data measured are part of a bigger project done in summer 2010 taking kinematical and the start is considered an important technical element in the sport of luge, it has not been force/acceleration records. We like to mention our co-researchers Gabe Fife from the University thoroughly studied to date. The purpose of this study was to compare duration of start Delaware, USA and David O'Sullivan of the University of Seoul, Korea. They concentrated on the elements typical to male and female lugers on an iced start ramp and on a luge track. This is force/acceleration values, which are not used within this paper. We also would like to thank Sara done in order to evaluate correspondence of athletes’ technique elements at training facilities Franco and Cristina Menescardi because of his help in the data acquisition process. to those shown at competition facilities.

METHODS: Timing data of seven athletes were collected for the purpose of this study: two elite level female athletes – athletes A1 and A2 – (weight 86.6 and 73.1 kg, height 174 and 173 cm, competitive experience 19 and 11 years), two junior level female athletes – athletes B1 and B2 – (weight 73.7 and 69.1 kg, height 175 and 169 cm, competitive experience 5 and 2 years), one junior male athlete – athlete C – (weight 86.8 kg, height 191 cm, competitive experience 3 years) and two elite level male athletes – athletes D1 and D2 – (weight 81.9 and 89.3 kg, height 184 and 176 cm, competitive experience 19 and 24 years). The athletes performed four starts daily on the luge track for two consecutive days; timing data from the start ramp were collected previously during training camps (partially reported for female and junior athletes by Fedotova & Pilipiv (2010a)). On the track male athletes started from men’s start and female athletes from ladies’ start that is located lower. In the sport of luge athletes begin in a sitting position; first they perform a rocking motion forth and back, then a forceful start jerk follows, and after that athletes continue accelerating the sled pushing-off the ice surface with their fingers or palms before assuming the riding position on the sled. Kempe and Thorhauer (1995) had divided lugers’ start into five phases: 1. Pushing the sled forward whilst holding the start handles; 2. Movement of the sled backwards or “compression” phase; 3. Push-off from the start handles; 4. Several paddling arm strokes and thrusting off the ice surface; 5. Assuming a supine race position on the sled.

ISBS 2011 222 Porto, Portugal