From block clearance to sprint running: Characteristics underlying an effective transition

Abstract The aim of this study was to characterize the specifics of the sprint technique during the transition from start block into sprint running in well-trained sprinters. Twenty-one sprinters (11 men and 10 women), equipped with 74 spherical reflective markers, executed an explosive start action. An opto-electronic motion analysis system consisting of 12 MX3 cameras (250 Hz; 325,000 pixels) and two Kistler force plates (1000 Hz) was used to collect the three-dimensional (3D) marker trajectories and ground reaction forces (Nexus, Vicon). The 3D kinematics, joint kinetics, and power were calculated (Opensim) and were time normalized to 100% from the first action after gunshot until the end of second stance after block clearance (Matlab). The results showed that during the first stance, power generation at the knee plays a significant role in obtaining an effective transition, representing 31% of power generation in the lower limb, in the absence of preceding power absorption. Furthermore, the sprinter actively searches a more forward leaning position to maximize horizontal velocity. Since success during sprinting from the second stance onwards involves high hip and ankle activation, the above-mentioned three characteristics are specific skills required to successfully conclude the transition from start block into sprint running.