The forces applied to the starting blocks are an important aspect of a sprint start. For achieving the most effective start, however, the relationship between these forces and block clearance has not been clarified. In this study, an experiment was conducted with collegiate sprinters in order to elucidate this relationship. The 19 male participants performed a start dash from the blocks as in a typical sprint race, and the forces applied to the front and rear starting blocks, as well as to the ground during the first step, were measured with force plates. The following results were obtained. Based on the impulses applied to the starting blocks, the horizontal impulse component had a greater effect than the vertical impulse component at block clearance. Furthermore, at block clearance, the horizontal component of the impulse applied to the front block accounted for a large proportion of the total horizontal impulse applied to the starting blocks. However, there was a significant correlation between the horizontal component of the impulse applied to the rear block and the total horizontal impulse applied to the starting blocks. The horizontal component of the impulse was affected by the duration of force application to the blocks. Moreover, the horizontal component of the impulse applied to the starting blocks was unrelated to block placement. This indicates that the component was affected by the position of the sprinter relative to the front and rear blocks. Lastly, the horizontal impulse component at block clearance affected the sprint start until grounding of the first step, after which this relationship differed according to the starting strategy and grounding skill of individual participants.<br>