Changes in running mechanics. over 100-m, 200-m and 400-m treadmill sprints

Purpose: Compare alterations in running mechanics during maximal treadmill sprints of different distances. Methods: Eleven physically active males performed short (100-m), medium (200-m) and long (400-m) running sprints on an instrumented treadmill. Continuous measurement of running kinetics/kinematics and spring-mass characteristics were recorded and values subsequently averaged over every 50-m distance intervals for comparison. Results: Compared with the initial 50 m, running velocity decreased (P < 0.001) by 8 +/- 2%, 20 +/- 4% and 39 +/- 7% at the end of the 100, 200 and 400-m, respectively. All sprint distances (except for step length in the 100-m) induced significantly longer (P < 0.05) contact times ( +7 +/- 4%, +22 +/- 8% and +36 +/- 13%) and lower step lengths (-1 +/- 4%, 5 +/- 5% and 41 +/- 2%) and frequencies (-6 +/- 3%, -13 +/- 7% and 22 8%) at the end of the 100-m, 200-m and 400-m, respectively. Larger reductions in ground reaction forces occurred in horizontal versus vertical direction, with greater changes with increasing sprinting distance (P < 0.05). Similarly, the magnitude of decrement in vertical stiffness increased with sprint distance (P < 0.05), while leg stiffness decreases were smaller and limited to 200-m and 400-m runs. Overall, we observed earlier and larger alterations for the 400-m compared with other distances. Conclusions: The magnitude of changes in running velocity and mechanics over short (100-m), medium (200-m) and long (400-m) treadmill sprints increases with sprint distance. The alterations in stride mechanics occur relatively earlier during the 400-m compared with the 100-m and 200-m runs. (C) 2016 Elsevier Ltd. All rights reserved.