KINEMATICS OF CLEAR IN JUNIOR BADMINTON PLAYERS
AbstractIntroduction the motion of rotating body segments of different shots in badminton can be described in terms of angular position, displacement, velocity or acceleration. The linear velocity of the rotating racket hitting the shuttle is directly proportional to the sum of both the angular velocity and the radius of rotation of the consecutive body segments in badminton strokes (Lee 1993). The timing of these consecutive rotational movements is important in relation to the hit of the racket with the shuttle (Gowitzke 1979).The linear momentum of the clearing arm and racket transfers to the shuttle according to the analogy of the force impulse and the change of linear momentum. The purpose of the present preliminary research was to' study the release velocity of the shuttle in maximal clear placing the shuttle on the opponent scourt in junior badminton players, to explain the produced angular and linear velocities and accelerations in the racket, hand, forearm, upper arm and trunk. METHODS Ten volunteer junior badminton player strained to perform maximal clears on the court. For motion analysis subjects performed a minimum of five successful clears. The fastest clear of every subject was selected for detailed analysis. Anthropometric data (Mean+S.D.) for the subjects was as follows: age 12.223.3years, height 1.562k0.137 m and mass46.85 11.0 kg. On average, they had training 1.851.7 years in badminton. Each clear was recorded for 3 D analysis with NAC 400 (side view) high speed video(100 fps) and Magnavox (back view)camcorder (60 fps). The optical axis of the cameras were perpendicular. The calibration scaling frame was rectangular with the dimensions of 2.0 m x 2.0-m x3.0 m. The same racket and shuttle were used in all measurements. An APAS was used to process frame crabbing, digitizing, smoothing (DLT) and transformation. The mechanical model of trunk, head, upper arm, lower arm and hand (twelwe points) was combined with the racket (four points) and shuttle. A descriptive analysis was performed on the differences in instantaneous positions, linear and rotational velocities. RESULTS The maximal release velocities of the shuttle were in the youngest subject (8years) and oldest one (19 years) 20.2and 56.0 ms-', respectively. The maximal linear velocities in the youngest and oldest subject were as follows: racket head 15.9 and 44.0 ms-' , wrist 4.7 and10.8 ms-', elbow 2.5 and 5.9 ms-' and shoulder 1.6 and 2.9 ms-', respectively. CONCLUSION In conclusion, the most experienced subject produced high speed for the shuttle through the kinematic chain of body segments with high angular and linear velocity through the impact of the shuttle and racket. The correct timing pattern of the consecutive body segments was also observed. The lengths and high angular velocities of the body segments were advantageous features for badminton players. REFERENCES Gowitzke, B.A. (1979) In: Science in Racquet Sports. J.Terauds (ed.) pp. 7-1 5.Del Mar, CA: Academic Publishers.Lee, K.B. (1993) In: Biomechanics inSports XI, J. Hamill. T.R. Derrick & E.H.Elliott (eds), pp. 239-242, University of Masschusetts, Amherst, MA.
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