Movement time
The first question of the study was to examine if the movement time will decrease when the speed of target increases? The result showed that when the speed of object increased, movement time did not change significantly. This result does not support previous studies of interceptive tasks that showed a tendency to move more quickly towards fast targets (which was moving away from the moving hand that was used to intercept the target) than towards slow ones (Bairstow, 1987). In addition, Brenner and Smeets (1996) showed that the greater the speed of objects the shorter the movement time. In the experiment conducted by Brouwer Brenner and Smeets (2002) suggested that, the movement time would be shorter when the speed of object increased. However, this did not show in the current study and this could be due to the difference in the nature of the tasks.
In Brouwer Brenner and Smeets (2002) the participant intercepted the target that moved at different constant speeds, which would disappear in sight. The disappearance of the target was carried out in a varying amount of time. In this way, it prevented the participant from updating the information during the time that the object disappeared. The target moved on the screen and the screen was right in front of the participant, and the participant had to strike the target with a 22cm Perspex rod. In the current study the speed of object also moved at different speed, however, the disappearance time were not used intentionally to manipulate the viewing time of the object. The target object was moving toward the participant but not away from the participant. Since the object was moving toward the participant the movement time might be limited because theincoming target may limit the distance for the participant to have the ability to move faster as the object speed increases and closing the spatial distance between the object and the participant.
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The time the object became visible for the participant was at the perpendicular level to the ground. All participants have limited time to react with the back kick, thus the capability of the participant for a back kick may be limited by the duration of time and the perceived object at the perpendicular level. In Taekwondo competition athletes can move back and forth for an offensive or defensive action; however, during the back kick experiment the participant were required to stay at the place (position) in a distance of their leg length to the target. Furthermore, they were asked not to move from their positions and attack the incoming object until they see it, they were unable to change their distance according to their own preference. This could influence the participant to improve their movement time.
Temporal error
In this study, the participants were instructed to kick as quickly and as accurately as possible once they see the object in the 3 speed conditions. For the current study, the temporal error is defined differently from those found in previous studies In a study conducted by Tresillian (2002), the participants were asked to intercept a moving target with a bat that moved along a straight path and it was constrained by a linear slide. The movement time used to intercept object decreases as the speed of object increases. The speed and object size was manipulated but it gave the same effect on required temporal precision, however the responses to these changes vary, because the target speed brings out larger changes in response speed. The temporal error in the current study is similar to a reaction time but it was a measure between the movement initiation and the moment when the sand bag arrived at the perpendicular level.
Because participants produced similar movement times at different target speed conditions, when the target moved in a faster speed, it was difficult for the participants to initiate the movement only after the target became visible at perpendicular. We could not tell if there was any anticipation in the participant because there was no significant effect of speed in TE. . There might be a possibility where the participant had a strategic plan in order to have a head
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start before seeing the target. For example, the participants might have noticed a bulge at the top of the cloth when the target is near perpendicular.
The no-difference result of the ANOVA may be because of the speeds of the objects were too fast for participants to kick giving them all similar approach to the incoming object. When combining the movement time result it could be seen that participants were not able to increase the kicking speed under the faster target speed conditions. Without appropriate starting signal to initiate the kicking movement, the initiations of the kicking movement were not systematically tied to the speeds of the target.
To sum up, we could not justify that a complete back kick should have the participant intercept the incoming object at the right time and place because the participant will be in contact with the sandbag even if they did not move. In previous study of Tresilian (2002), the participants intercepted a moving object requiring that the interceptive effector (hand or bat) get to the right place at the right time. In addition, in Tresilians (2002), the moving object was moving across the participant, where in this study the object was moving toward the participant, which resulted in a different task. Generally speaking Taekwondo athletes need to have the right TE for the best timing to contact the opponent before the opponent reaches you, and this may vary between people because there are many aspect we need to take into account. The height, movement speed, and reaction time, etc.. The result of this study showed no significant speed effect because the experimental manipulation did not reflect the real life competition.
Target Spatial Accuracy
In this study, the participants were asked to kick as accurately as possible for the incoming object and instructed that the points scored on the target from the bullseye outward were 4, 3, 2, and 1 and 0 points for the kicks missed on the target. The effect of target speed on spatial accuracy was investigated where the SP1 is at stationary. The target spatial accuracy of SP1 was the greatest compared to those of the other speed conditions because the target in SP1 was
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stationary and visible the entire time to the participant. The distribution of the points scored were significantly associated to the 4 speed conditions, which showed similarity to Brouwer (2002) as the target speed increases it is more difficult to hit the target. The accuracy rate was (73%) for the fastest target and the slow target was (81%). However the target was moving away and not moving toward the participant. Whereas in the current study the participant tried to execute the back kick task where the target was moving toward the participant and the participant were moving directly to the target (Brouwer, Brenner,& Smeets, 2002).
The results of spatial accuracy from the current study did not show similarity to the speed-and-accuracy trade-off phenomenon reported in the literatures (e.g., Woodworth, 1899;
Fitts, 1954; Fitts & Perterson, 1964). Although there are similarities in this study that gives the speed and accuracy trade-off, but the given tasks were completely different. In the present study, target moves toward the participant, at the same time the participant moves to the target whereas in studies that followed Fitts’ paradigm, the target remained stationary and the distances were manipulated. However, when the participants were instructed to move as quickly and as accurately to the target as possible, they were unable to increase their speed as the target speed increased. Since the MT remained the same and the distance did not change or shortened therefore it did not show the same effect as the speed and accuracy trade-off.
Spatial accuracy of angular position at foot-target contact
There was a significant association between the target speed and the level of angular position at foot-target contact. However, we did not see if the participant adopted an anticipation strategy because there was no significant speed effect in the TE from the movement initiation, we could not say that the participant moved ahead of the sand bag before reaching perpendicular. The result of ASA level showed that the target speed was fast in SP3 and SP4 for them to strike the target at the perpendicular position, thus as the speed of target increased it was more difficult for participants to hit the target near 0° perpendicular to the
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ground. Since there was also no significant speed effect in movement time, the participant was limited to perform a better ASA.
When the moving target was coming toward the participant at SP3 and SP4, the target speed increased yet the movement time did not decrease which made the position of the target at the foot-target contact further away from the perpendicular. The kicking foot could not contact the moving target in an optimal timing but the kicking foot and the moving target would just collide in their paths. Therefore the spatiotemporal constraint does not only depend on the speed of the target and the chosen mode of interception such as kicking, but also on how the person moves and how they are positioned relative to the target paths of motion.
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Conclusions
In this study we found out that elite Taekwondo athletes movement time and the temporal error were not influenced by the speed of the target. Participants have reached the speed limit over the training. It is not likely that they can shorten the movement time any further, therefore it is very difficult for one to suddenly increase the movement speed when the speed of object increases. As the speed of object increased the spatial accuracy, both on target and at the foot-target contact position (ASA), decreased.
For future study, we could manipulate both the target size and speed such as in Tresillian (2002), to see if the manipulations can influence the movement time of the participant.
Moreover, we can include different technique such as pushing kick in the experiment and manipulate the different visibility of the object to see if we have the same effect as Brouwer, Brenner and Smeets (2002). We may also manipulate different viewing time of the moving object the for participants (Brouwer, Brenner & Smeets, 2002; Tresilian, 2002) to examine if MT will decrease as the target speed increases at the longer viewing time.
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REFERENCES
Bairstow, P. J. (1987). Analysis of hand movement to moving targets. Human Movement Science, 6(3), 205-231
Brenner, E., & Smeets, J. B. (1997). Fast responses of the human hand to changes in target position. Journal of Motor Behavior, 29(4), 297-310.
Brenner, E., Smeets, J. B., & de Lussanet, M. H. (1998). Hitting moving targets continuous control of the acceleration of the hand on the basis of the target’s velocity. Experimental Brain Research, 122(4), 467-474.
Brenner, E., & Smeets, J. B. (2010). How well can people judge when something happened?
Vision Research, 50(12), 1101-1108.
Brouwer, A. M., Brenner, E., & Smeets, J. B. (2002). Hitting moving objects: is target speed used in guiding the hand? Experimental Brain Research, 143(2), 198-211.
Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences, 2nd ed. Hillsdale, New Jersey: ErkBaum
Daum, M. M., Huber, S., & Krist, H. (2007). Controlling reaching movements with predictable and unpredictable target motion in 10-year-old children and adults.
Experimental Brain Research, 177(4), 483-492.
Falco, C., Alvarez, O., Castillo, I., Estevan, I., Martos, J., Mugarra, F., & Iradi, A. (2009).
Influence of the distance in a roundhouse kick's execution time and impact force in Taekwondo. Journal of biomechanics, 42(3), 242-248.
Falco, C., Landeo, R., Menescardi, C., Bermejo, J. L., & Estevan, I. (2012). Match analysis in a university taekwondo championship. Advances in Physical Education, 2(01), 28.
Ferrie, E. (1989). Taekwondo: traditional art and modern sport. Crowood.
Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6), 381.
28
Hsieh, T. Y. (2015). Entropy of speed and accuracy trade-off in space-time. The Pennsylvania State University.
Jakubiak, N., & Saunders, D. H. (2008). The feasibility and efficacy of elastic resistance training for improving the velocity of the Olympic Taekwondo turning kick. The Journal of Strength & Conditioning Research, 22(4), 1194-1197.
Kazemi, M., Waalen, J., Morgan, C., & White, A. R. (2006). A profile of Olympic Taekwondo competitors. Journal of sports science & medicine, 5(CSSI), 114-121.
Kim, J., Yenuga, S. S., & Kwon, Y. (2008). The effect of target distance on trunk, pelvis, and kicking leg kinematics in Taekwondo round house kick. In ISBS-Conference Proceedings Archive (Vol. 1, No. 1).
Kim, Y. K., Kim, Y. H., & Im, S. J. (2011). Inter-joint coordination in producing kicking velocity of Taekwondo kicks. Journal of Sports Science & Medicine, 10(1), 31.
Koh, J. O., & Watkinson, E. J. (2002). Video analysis of blows to the head and face at the 1999 World Taekwondo Championships. Journal of Sports Medicine and Physical Fitness, 42(3), 348.
Lee, C. L., & Chen, A. H. (2008). The support leg and attack pattern relationship of back kick movement in taekwondo. In ISBS-Conference Proceedings Archive (Vol. 1, No. 1).
Lee, C. L., Chin, Y. F., & Liu, Y. (2008, March). Comparing the difference between front-leg and back-leg round-house kicks attacking movement abilities in taekwondo. In ISBS-Conference Proceedings Archive (Vol. 1, No. 1).
Lee, D. N., Young, D. S., Reddish, P. E., Lough, S., & Clayton, T. M. H. (1983). Visual timing in hitting an accelerating ball. The Quarterly Journal of Experimental Psychology, 35(2), 333-346.
Lee, S. K. (1983). Frequency analysis of the Taekwondo techniques used in a tournament.
Journal of Taekwondo, 46, 122-130.
Li, F. X. (1996). Effect of Bali Mass and Bali Momentum in Interceptive Task. Studies in Ecological Psychology, 53.
29
Mason, A. H., & Carnahan, H. (1999). Target viewing time and velocity effects on prehension.
Experimental Brain Research, 127(1), 83-94.
Park, Y. H., & Seabourne, T. (1997). Taekwondo techniques & tactics. Human Kinetics 1.
Plamondon, R., & Alimi, A. M. (1997). Speed/accuracy trade-offs in target-directed movements. Behavioral and Brain Sciences, 20(02), 279-303.
Schmidt, R. A., Sherwood, D. E., Zelaznik, H. N., & Leikind, B. J. (1985). Speed-accuracy trade-offs in motor behavior: Theories of impulse variability. In Motor Behavior (pp.
79-123). Springer Berlin Heidelberg.
Tan, Y. L., & Krasilshchikov, O. (2015). Diversity of attacking actions in Malaysian junior and senior taekwondo players. International Journal of Performance Analysis in Sport, 15(3), 913-923
Tresilian, J. R. (1999). Visually timed action: time-out for ‘tau’?. Trends in Cognitive Sciences, 3(8), 301-310.
Tresilian, J.R., Oliver, J., & Carroll, T. (2003). Temporal precision of interceptive action:
differential effects of target size and speed. Experimental Brain Research, 148(4), 425-438.
Tresilian, J. R., & Lonergan, A. (2002). Intercepting a moving target: effects of temporal precision constraints and movement amplitude. Experimental Brain Research, 142(2), 193-207.
van Donkelaar, P., & Lee, R. G. (1994). The role of vision and eye motion during reaching to intercept moving targets. Human Movement Science, 13(6), 765-783
van den Tillaar, R., & Ulvik, A. (2014). Influence of instruction on velocity and accuracy in soccer kicking of experienced soccer players. Journal of motor behavior, 46(5), 287-291.