Influence of Initial Pelvic Tilt on Vertical Jump Height

INTRODUCTION Vertical jumps have been fully studied during the last thirty years. Especially maximal vertical jumps used to be analyzed, which maximal vertical jump height was considered as the main factor of the performance. Maximal vertical jump height depends on effective energy, the sum of potential and “vertical kinetic energy” (i.e. kinetic energy due to vertical velocity) of the body mass center (BMC). Therefore, in order to reach a maximal jump height, it is necessary to increase vertical position of BMC and vertical velocity of BMC as high as possible at takeoff. To understand which patterns individuals use to perform maximal vertical jumps, the body was simplified into a four rigid segment model in the sagittal plane. It was composed of the feet, the shanks, the thighs and the segment “HeadArm-Trunk” (HAT) and of three joints (ankle, knee, hip) [1]. Muscles crossing these joints would produce work when shortening and would contribute to the increase of height of the BMC during vertical jumps. Nevertheless the HAT segment is not a single rigid segment. Especially the trunk could be divided into the pelvis and the rachis which could be divided into several segments. Therefore it could be hypothesis that hip and trunk muscles crossing these joints, resulting from these several segments, could contribute to the increase of the height of the BMC.