Kinematic Analysis and Optimization of Jerk Considering Elasticity of Weightlifting Bar and Damping Effect of Body in Clean and Jerk

Abstract

ABSTRACT The purpose of this study is kinematic analysis and optimization of jerk considering elasticity of the weightlifting bar and damping effect of the body. In order for weightlifters to achieve good technical skills in clean and jerk, the elasticity of weightlifting bar needs to be examined. First of all, barbell's trajectory, which leads to derivation of barbell's velocity and acceleration over time, is tracked by using image processing technology such as pattern recognition from video clip filmed the lifter's performance. Since the pull used during the clean is similar to the pull used during the snatch, the focus is set on examination of the jerk. Five kinematic characteristics—“Jerk‐Preparing‐Time,” “Jerk‐Drive‐Velocity,” “Jerk‐Time,” “Jerk‐Offset,” and “Jerk‐Drop” are newly introduced to evaluate the jerk technique. Then, a kinematic model which is comprised of springs and dashpots is proposed in order to simulate and optimize the jerk using elasticity of weightlifting bar. Spring constant and damping coefficient of the model is estimated by analyzing the barbell's oscillation on the shoulders. Besides, spring constant is calculated by theory of bending of beam, as well. Finally, an optimal control problem based on the proposed kinematic model is formulated to optimize the jerk. The methodology is illustrated with case study, showing good agreement with actual lifts. It could be useful for improving the jerk technique.

Keywords

• clean and jerk
• elasticity
• kinematic model
• optimization
• weightlifting bar