Mechanics of standing and crouching sprint starts

The aim of this study was to compare the kinetic and kinematic parameters of standing and crouch sprint starts. Parallel starts (PS), false starts (FS), jump starts (JS) and crouch starts (3PS) were compared. Eighteen participants performed each start on a force plate and six infrared cameras captured the three-dimensional coordinates of 36 retro-reflective markers. Performance during a five-metre sprint (T_5m) was analysed. Duration of the start phase (T_start), mean values of horizontal and total ground reaction forces (GRFs) (F_{x_mean} and F_{tot_mean}), ratio of force (RF), maximal power (P_max) and kinetic energy (KE) of each limb were calculated. Significant differences were found for T_5m, T_start, KE, P_max, F_{x_mean}, F_{tot_mean} and RF for the crouch start compared to the other starts (P ≤ 0.05). Significant correlations were found between T_5m and T_start (r = 0.59; P ≤ 0.001), and T_5m and P_max, F_{x_mean} and RF (-0.73 ≤ r ≤ -0.61; P ≤ 0.001). To conclude, the crouch start resulted in the best performance because T_start was shorter, producing greater P_max, F_{x_mean} with a more forward orientation of the resultant force. Greater KE of the trunk in each start condition demonstrated the role of the trunk in generating forward translation of the centre of mass (CM).