THE VELOCITY OF THE JOINT ROTATION EFFECT TO BALL SPEED IN SEPAKTAKRAW SOMERSAULT KICK

Abstract

     Three main skills require using as basic technics in sepaktakraw such as serving, setting, and smash. From these skills, the smash is the skill which makes a score most consisted of many types including sunback, half-roll spike, and somersault kick. The sepaktakraw somersault kick has been used most due to all of smash skills. From previous evidence revealed that the sepaktakraw somersault kick skill is more effective than other skills.²⁴ The technic of the sepaktakraw somersault kick performs similarly to acrobatic activation which has to gesticulate in the air.⁵ Exclusivity of this skill, the subject performs higher trunk rotation which led to the contribution of many joints rotation in the sepaktakraw somersault kick players.
     The contribution of the joint rotation is considered by the angular velocity of many joints.¹⁷ Smash is one of sepaktakaw skill using the contribution of angular velocity of the joints, which includes the angular velocity of trunk, pelvis, hip, knee, and ankle.¹⁴ In addition; the effective ball speed is involved with leg length. The previous study recommended that the sepaktakraw players can do somersault kick effectively, due to having the kinematics components including the leg length and leg muscle power, the speed of body rotation,body height, leg flexibility and ability.⁵ The linear velocity determines as kicking (e.g. radius is length of the legs, linear velocity is speed for foot, angular velocity is the angular velocity of the joints) . If the angular velocity is constant, the speed of foot is varied with length of legs affected on the ball speed.¹⁶
     The sepaktakraw somersault kick is the motion which use in several country especially in competition games. There are limited researches of sepaktakraw somersault kick, especially in the major of biomechanics.
The pilot study does not explain the variables of kinematics which affect the ball speed in doing the sepaktakraw somersault kick. In this study the researcher focused on the kinematics 3D of trunk and lower extremities including pelvis, thigh, shank, and foot, as doing the sepaktakraw somersault kick related with the ball speed.