KINEMATIC AND DYNAMIC ANALYSIS OF THE 'MAWASHI-GHERI'

Abstract

Introduction Although three-dimensional kinematic and dynamic movement analysis becomes a standard methodological technique in biomechanics, it is rarely used in service of teachers in the field. This study examines the possibilities to infer didactical useful information for teaching the 'Mawashi-Gheri', a complex roundhouse kicking movement in karate. Methods Three karate-teachers, selected for their excellence in the studied technique, performed the movement several times. Each time, three-dimensional kinematic (Vicon-system, 60 Hz, 10 markers) and dynamic data Kistler Forceplate, 600 Hz) were acquired. Data were saved on computer disc only if these experts agreed on the goodness of there performance. Afterwards, four children (aged 12 to 15 y.) imitated the movement. Two of them were appreciated to be advanced karate-pupils, the other two sojourned at the beginning level. Additionally, data regarding flexibility, equilibrium and kinantropometry were gathered in order to provide a referential base to interpret differences in execution among these subjects. Reactionforces were integrated using Simpson's Method to get the velocity and displacement of the center of gravity. Filmdata were interpolated (Free Cubic Spline), digital low-pass filtered and differentiated (Usui 1982) to obtain displacement, velocity and acceleration courses of seven segments (feet, shanks, thighs and trunk). Special attention was payed to the initial orientation and angular displacement of the shoulders, pelvis and suporting foot. Kinantropometric data were processed using a simplified Hanavan model (1964) to estimate individual segmental parameters (mass, masslocation and inertia). Finally, all data were reduced into 33 descriptive parameters Results and discussion Intra-individual differences among subsequent executions of the studied technique are very small in skilled subjects. However, interindividual differences are large, even among subjects of a same skill level. This could mean that exercise tends to stereotype movement patterns, even for a fast and complex movement of this kind, but these patterns are personal. The most important differences among skilled and beginning combatants are to be found in the timing and duration of the various actions in the movement. This results in very different shaped velocity and acceleration curves. As a matter of fact, the actual lash is only visible in the force registrations of good performers and occupies only 50 to 55 msec. Maximum velocities of beginners are about 60 % of those attained by experts. It is presumed that the incapacity of beginners to produce high velocities in this kicking movement can be attributed to a wrong sequence of rotational movements. Conclussion The 'Mawashi-Gheri' is a highly three-dimensional movement. Attempts to study this movement in a planar space risk to overlook the important torsion component which tends to be the discriminating factor between skilled and beginning karate-combatants.