The role of the starting block in sprinting and its influence on a crouch start

Abstract

The role of the starting block in sprinting and its in‰uence on a crouch start. Japan J. Phys. Educ. Hlth. Sport Sci. 60: 667 684, December, 2015 AbstractStarting blocks are required for sprint starts in competitive races. Here, we examined the functional role of starting blocks at the start of a sprint. The participants were 9 sprinters (height: 174.8 ±3.7 cm; weight: 69.0±4.5 kg; personal best 100 m time: 10.89±0.34 s) who performed 2 kinds of sprint start: a crouch start with starting blocks (BS), and a crouch start without starting blocks (CS). Two force plates were placed under each block or under the participants' feet in the BS or CS, respectively, and were used to measure the force applied to the starting blocks or to the ground. Another 2 force plates were placed to measure the ground reaction force of theˆrst and second steps after block clearance. The sampling frequency for these measurements was 1 kHz, and kinematic data were recorded using 4 high speed cameras at 250 frames/s. Time from the start signal to take-oŠ of the second step was signiˆcantly longer for CS than for BS, but there was no signiˆcant inter-group diŠerence in the point of touchdown of the second step. The method of increasing the horizontal velocity of the center of gravity diŠered signiˆcantly by group and power in the horizontal direction during the block clearance phase, being signiˆcantly less for CS than for BS. Consequently, the horizontal impulse applied to the ground in CS was signiˆcantly less than that applied to the starting blocks in BS, and the duration of force application in CS was signiˆcantly longer. Furthermore, the horizontal impulse applied by the rear foot in CS was signiˆcantly less than that applied to the rear block in BS, and the horizontal impulse applied during the double stance phase in CS was signiˆcantly less than that in BS. These factors aŠect the extensional and rotational movements in the block clearance phase. Taken together, these results indicate that the crouch start can be eŠective when starting blocks are used. Therefore, starting blocks can be regarded as an essential tool for enhancing sprint start performance.