Weightlifting is one of the Olympic sports, which is divided into two lifts: snatch and jerk. In the clean and jerk, the barbell is first lifted above the chest and then jerked overhead. Barbell’s trajectory and kinematic characteristics such as velocity are important factors for evaluating weightlifting technique.
Previous studies revealed some drawbacks in the research into the jerk in clean and jerk. They paid little attention to the elasticity of the weightlifting bar, which is not a rigid body. Therefore, effective use of the elasticity enables lifting more weight.
Jon Min Hyok, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has investigated the kinematic analysis and optimization of jerk considering the elasticity of weightlifting bar and the damping effect of the body, to help weightlifters to achieve good technical skills for clean and jerk.
First of all, in order to derive the barbell’s velocity and acceleration over time, he tracked the barbell’s trajectory from the video clip of lifter’s performance by using image processing technologies such as pattern recognition. Since the pulling action of jerk is similar to that of snatch, he set focus only on jerking. To evaluate jerk technique, he newly introduced five kinematic characteristics “Jerk-Preparing-Time, ” “Jerk-Drive-Velocity, ” “Jerk-Time, ” “Jerk-Offset, ” and “Jerk-Drop”. Then, he proposed a kinematic model comprised of springs and dashpots in order to simulate and optimize the jerk using the elasticity of weightlifting bar. He estimated the spring constant and damping coefficient of the model by analyzing the barbell’s oscillation on the shoulders. He also calculated the spring constant by the theory of bending of beam. Finally, he formulated an optimal control problem based on the proposed kinematic model to optimize jerk.
The advantages of the proposed method are its simplicity, flexibility and no need for any equipment except a camera. It will help coaches or weightlifters improve their jerk technique based on correct numerical evaluation.
For the details, please refer to his paper “Kinematic Analysis and Optimization of Jerk Considering Elasticity of Weightlifting Bar and Damping Effect of Body in Clean and Jerk” in “Engineering Reports” (EI).
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