Kick techniques of error detection and prevention in taekwon-do itf

Taekwon-do ITF (International Taekwon-do federation) is a combat sport involving large number of kicks; it requires rapid and forceful kicking (Saulite 2010).
About fifty percent of taekwon-do ITF fight skills are related to the kicking techniques. Effective taekwon-do kicking techniques are most difficult to perfect, and require the use of the entire body to apply optimum force from a limited base of support (Shirley 1992).

In Taekwon-do movement studies mainly visual control methods are used (Романенко 2007). Instrumental methods would allow achieving not only qualitative, but also quantitative measures of movements of athletes (Гавердовский 2007). The aim of the research is to find technical errors of athletes, which influence the time of the frontal roundhouse kick.

Methods
The subjects of the research are 10 taekwon-do athletes (age: 13±1.4 years, height: 166±6 cm, weight: 45±7 kg; experience in sports: 4±1.2 years), with blue and green-belt levels.
Athletes performed roundhouse kick from still position with front leg two times. Movement analysis was performed using two high speed Basler A602fc cameras (100 Hz) and SIMI Motion software. Light-reflecting markers were placed on three body landmarks: hip (Trochanter Major), knee (Condylus Lateralis) and ankle (Malleolus Lateralis). Cameras were located on one side of the calibrated movement volume at angles, which provide for both cameras maximal visibility of all three markers during the whole studied range of the movement. After video recording of the movements points were digitized with SIMI Motion 3D software.

Results.
Analysis of high speed video records allowed estimating biomechanical characteristics of the frontal roundhouse kick. To establish more rational kicking technique the kick time was correlated with the following biomechanical parameters: maximal knee flexion angle at the end of preparatory phase, and ratio of kick preparatory phase time to kick execution phase time.

Figure 1. Correlation between angle of knee maximal flexion and time of kick
Figure 2. Correlation between preparatory and kick phase proportion and time of kick

Relationship between maximal knee flexion angle and the kick time, and relationship between ratio of longer preparatory phase to shorter kicking phase and the kick time was estimated (α < 0.01).

Conclusions.
1. After analysis of biomechanical parameters of roundhouse kick it was concluded that athletes with smaller angle during maximal knee flexion also have a shorter kicking time, the same was true for those athletes having preparatory phase longer than kicking phase.
2. When mastering the roundhouse kick technique more attention should be paid to knee flexion in preparatory phase in order to achieve shorter kicking time.
3. We suppose that decrease of kicking time at smaller knee angles in initial phase is related to decrease of moment of inertia.
4. Decrease of kicking time in this case may be also related to more active use of thigh frontal muscles (Quadriceps femoris) in eccentric mode.

References.
1. Гавердовский Ю.К. (2007). Обучение спортивным упражнениям. Биомеханика. Методология. Дидактика. – Москва: Физкультура и спорт, 912 с.
2. Романенко В.В. (2007). Построение биомеханических моделей основных технических приѐмов выполняемых ногами для таэквондистов-новичков // Слобожанський науково-спортивний вісник: Зб.наук. пр. – Харьков: ХДАФК. – No 12, c.281-285.
3. Saulite S., Cupriks L., Fedotova V. (2010). Biomechanical analysis of taekwon-do ITF front-leg rounhouse kick. 3rd Baltic Sport Science conference. Physical activity and sport in changing society: research, theory, practice and management. Abstracts. April 29 - May 1, 2010, Riga, Latvia, pp. 48-49.
4. Shirley Mark E. (1992). The taekwondo side kick: a kinesiological analysis with strength and conditioning principles. National Strength and Conditioning Association Journal. Volume 14, Number 5, pp. 7.

Sergejs Saulite, Leonids Cupriks, Veronika Fedotova