The sprint start consists of three transitions defined by the instants the hands, rear leg and front leg leave the ground, which delimit three phases. Ground reaction forces produced by 57 sprinters during the block phase were analysed to investigate the performance (average horizontal external power) implications of transition timing and the force production and centre of mass (CM) displacements between them. Better sprint starters exhibited higher horizontal (r = 0.47 for phase two), but lower vertical (r = -0.40), CM displacement across shorter time periods. Additionally, more horizontally-orientated force vectors to reduce CM projection angle at each transition were favourable (r range = -0.62 to -0.45). Coaches should encourage high anteroposterior bilateral force production even though this may compromise (r = -0.41) subsequent front block force production.
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