In a competitive swimming race event, the back plate can be placed on the starting block. Although the back plate has diŠerent setting positions, the eŠect of the plate position on start performance has not yet been clariˆed. This study was conducted to investigate the eŠect of the back plate position on the kick-start performance of competitive swimmers. Six male swimmers dived from an instrumented starting block that contained 2 force plates and force sensors to measure the reaction forces exerted by the hands and front and rear feet. Four high-speed cameras were used to obtain kinematic data on the swimmers. The horizontal take-oŠ velocity of the front plate position resulted in a better outcome than the back plate position (p<0.05). In the front plate position, a longer rear foot contact time generated a large impulse, and swimmers were able to achieve a higher take-oŠ velocity. To generate a larger impulse, the contact time on the starting block needed to be longer. However, swimmers were able to achieve a higher take-oŠ velocity using the front plate position without extending the block time. In this manner, the front plate position did not aŠect the time on the block. Moreover, diŠerent setting positions of the back plate in‰uenced the joint angle of the postural set before the starting signal. DiŠerences in the joint angle led to an increase in the horizontal component of the force impulse of the rear leg. Therefore, revealing the relationship between the joint angle of the postural set and start performance would provide detailed information on the optimum start posture for swimmers, including the plate position. Key wordshorizontal reaction force, horizontal take-oŠ velocity, rear foot oŠ time, rear foot reaction force, 10 m-time キーワード水平反力,跳び出し水平速度,後足離れ時間,後足反力,10 m 通過時間