Principle Component Analysis of the Mechanics of the eccentric and concentric Phases of the Hopping

Abstract

Abstract The Stiffness of humans could have a substantial effect on motion efficiency by the influence in the Stretch-Shortening cycle. The purpose of this study was to investigate the relationship between mechanics of the negative eccentric and positive concentric phases of hopping; to identify the relationship between stiffness and stretch-shortening cycle during submaximal cyclic motions. stretch-shortening cycle on the optimal performance of the cyclic movements. Materials and Methods: To calculate the leg stiffness, knee, and ankle joint stiffness and also angular velocity of the 30 young male with the age range of 18-33 and weight range of 60-88 kg during hopping, we used motion analysis and force platform system. Results: the results of the Principle component analysis showed that all of the ankles related parameters were classified on the first PC. Pearson correlation coefficient also showed that there is a significant relationship between joint stiffness, negative and positive mechanical energy and angular velocity (P<0.05, P<0.01). Conclusion: Due to the results of this study, it seems that during cyclic motions, the ankle joint is the main joint to determine if leg mechanics, more than knee joint. also, it was shown that there is a strong relationship between ankle joint kinematics and energetics of negative and positive phases of hopping. These relationships of ankle joint kinematics and energetics show that the stretch-shortening cycle in ankle joint is considered important so that all of the mechanical parameters of the negative phase have contribute to the increase of the positive phase of hopping and performance.