2014 Volume 59 Issue 2 Pages 887-904
Block clearance at the start of a sprint is a crucial phase of the race. However, the relationship between the force applied during the block clearance phase and the block clearance movement from the set position has not been entirely clarified. In this study, we examined this relationship by focusing on the behavior of the center of gravity of the whole body during the block clearance phase in a crouching start. Eight sprinters performed a starting dash from a starting block, as would occur in a sprint race. During the block clearance phase, the forces applied to the front and rear starting blocks were measured, and the block clearance movements were analyzed. The force applied during the block clearance phase was evaluated for whether it was close to the horizontal direction on the basis of the BLC (BLC=horizontal component of the impulse applied to the starting blocks/impulse applied to the starting blocks). There was a significant relationship (p<0.05) between the BLC and the angular displacement of the angle of the trunk during the block clearance phase. Also, the BLC was related to the rotational movement in the block clearance phase. In the entire block clearance phase for a high-BLC subject, the extensional movement occurred after the rotational movement. These sequences in movement of the whole body resulted in the center of gravity of the whole body being close to the horizontal direction. Furthermore, there was a significant relationship (p<0.05) between the BLC and the trunk angle at foot strike on the first step. Thus, during the block clearance phase in a crouching start, it is important for sprinters to accelerate their whole body close to the horizontal, applying their force to the starting block. This acceleration may result in horizontal movement of the body with lowering of the torso.