Quantification of functions of support leg joints during braking phase of cutting motion

Abstract

The purpose of this study was to quantify the functions of the support leg joints during braking phase of cutting motion int the generation of the ground reaction force. The ability of performing a quick cutting motion is an essential factor in ball sports, such as basketball, handball, and tennis. The cutting motion can be divided into two phases. One is braking phase and the other is accelerating phase. Quick cutting motion requires generating large ground reaction force in the approaching direction during the braking phase, where the force is generated by the lower limb joint torques. Participants performed a cutting motion with 180-degree turning movement and sidestep movement with different number of approaching steps. Three-dimensional coordinate data of 47 reflective markers attached to the whole-body were measured with a motion capture system with two force platforms. Dynamic contributions of the support leg joint torques to the generation of the individual components of the ground reaction force were obtained from the equation of the 3-segment multi-linked system of the support leg, where the equation of the motion was derived from the combination of the three equations of motion for the individual segments, such as the equations for constraint conditions arising from the connection of adjacent segments at joints, and the equations for anatomical constraint axes at certain joints. The result obtained in this study shows that the ankle plantar-dorsal and ankle eversion-inversion torque are main contributors to the generation of the individual components of the ground reaction force during the braking phase.