Introduction

1. BIOMECHANICS OF THE KARATE FRONT-KICK D. Gordon E. Robertson, Carlos Fernando, Michael Hart and François Beaulieu School of Human Kinetics, University of Ottawa, Ontario, CANADA, K1N 6N5 Introduction The front-kick (mae geri) in karate is one of the strongest and most easily mastered kicks. This project examined the powers produced by the lower extremity joints of the kicking leg of two elite (fourth dan) martial artists performing both closed and open stance front-kicks. Results The moments and powers of the ankle were insignificant and are not reported. The angular velocities, net moments of force and the powers produced at the knee and hip for a typical open stance kick appear in Figure 2. Two arrows indicate when the foot left the ground and when it contacted the pad. Purpose The purpose was to determine the contributions and sequencing of the ankle, knee and hip moments during the Karate front-kick (mae geri). Discussion The powers produced by the open stance kicks, as expected, always produced larger moments and powers than the closed stance kicks. Obviously, the added range of motion and greater pre-stretch enabled the subjects to generate greater impulses and foot velocities.   The sequencing of the moments were consistent across all trials and both subjects. The motion began with almost simultaneous flexing of the hip and knee joints. The hip flexors were responsible for flexing both joints as shown by the burst of positive work done by the hip flexors while the knee moment of force was relatively unproductive. After the hip reached maximum flexion velocity, the hip moment of force became extensor (presumably due to eccentric contraction of the gluteals) causing the hip to slow its flexion and initiate knee extension (whip action). Not surprisingly, based on similar research on the mechanics of soccer kicking (Roberson & Mosher, 1985) and sprinting (Lemaire & Robertson, 1989) the knee extensor moments did not contribute to knee extension. Instead, the knee moment was flexor producing negative (eccentric) work to presumably protect the knee from hyperextension at the end of the kick. Methods Two subjects with fourth Dan levels (black belts) were videotaped while kicking from both open (feet apart) and closed (feet together) stances at a kicking pad. The subjects performed five kicks each with the support leg on a force platform. Reflective markers were only placed on the kicking leg. Inverse dynamics was used to compute the net moments and their powers produced at the ankle, knee and hip. Figure 1 shows the experimental setup and a stick-figure and profile representation of a typical open-stance kick. References Lemaire ED,Robertson DGE (1989) Track & Field J, 35:13-17. Park, YJ (1989) A biomechanical analysis of Taekwondo front-kicks, Unpublished Ph.D. dissertation, U. Minnesota. Robertson DGE, Mosher RE (1985) Biomechanics IX-B, 533-538 Robertson DGE (2002) Biomech Motion Analysis System, http://www.health.uottawa.ca/biomech/-software. Sorensen H, Zacho M, Simonsen EB, Dyhre-Poulsen P, Klausen K (1996) J Sports Sci, 14:483-495. Figure 2. Typical angular velocities (top), moments of force (middle) and moment powers (bottom) of the knee and hip moments during an open stance karate front-kick. Left arrow indicates lifting of kicking leg; right arrow is contact. Positive angular velocities and moments of the knee are flexor; positive angular velocities and moments of the hip are extensor. Figure 1. Stick-figure and profiles of closed-stance front-kick Biomechanics Laboratory