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Relationship between the force applied to the starting block and movement during the block clearance phase in a crouching start.

AbstractThis study aimed to clarify the composition of the phases (acceleration, full sprint, and velocity endurance) in the 50-m sprint as performed by elementary school students, focusing on changes in running velocity. The subjects were 169 boys and 178 girls in theˆrst to sixth grades of elementary school, who performed a 50-m sprint from a standing start. Running velocity was measured using a laser distance meter, which was synchronized with a video camera that recorded the entire sprint. It was found that the running time of the total sprint was signiˆcantly shorter and that maximal velocity was signiˆcantly higher for higher-grade than for lower-grade students. The distances of the acceleration phase and full sprint phase were signiˆcantly longer for higher-grade than for lower-grade students, but there was no signiˆcant diŠerence in the duration of these phases by grade. However, both the distance and duration of the velocity endurance phase were signiˆcantly shorter for highergrade than for lower-grade students.Step length in the acceleration, full sprint, and velocity endurance phases was longer for higher-grade than for lower-grade students. However, step frequency at each phase tended to be almost equal or slightly lower for higher-grade than for lower-grade students. The SL index for higher-grade boys tended to be higher than for lower-grade boys. However, for girls, there was little diŠerence in the SL index at each phase for second-grade students or above. Taken together, the results indicate that the velocity endurance phase comprises the majority of the 50-m sprint when performed by lower-grade students. However, for higher-grade students, the velocity endurance phase is shorter due to the relative increases in the acceleration and sprint phases. This suggests that the distance of the acceleration and full sprint phases aŠects the distance and duration of the velocity endurance phase.