Dynamic analysis and optimization of snatch lift based on barbell trajectory and on an anthropometric model comprised of six links

Weightlifting requires explosive strength, high speed, and flexibility. The aim of this research is to present a method based on barbell trajectory and on an anthropometric model comprised of six links for dynamic analysis and optimization of snatch lift. First, snatch lift is divided into nine stages based on barbell trajectory, velocity, and acceleration, while evaluating dynamic characteristics. Then, an anthropometric model of weightlifter which is comprised of six segments: shin, thigh, trunk, upper arm, forearm, and head is developed. Since the head accounts for more or less than 10% of body weight, it should be considered as one link of one degree of freedom. Physical properties such as mass and center of mass of each link are not given by statistical data, but by anthropometry and calculation in Solidworks program. Finally, for barbell trajectory as one of the most important performance indices in weightlifting, an optimal control problem is formulated to minimize a criterion function defined as the sum of work done by lifter during snatch lift and solved by using Pontryagin Maximum Principle (PMP). The proposed method is illustrated with case study, showing results in good agreement with ones by analysis of lifter's actual performances. It can help coach or weightlifter to improve the snatch technique.