Abstract
The effect of the inclusion of a high hurdle 13.72 m after the start line on elite sprint start and initial acceleration technique has yet to be investigated or understood. This highly novel study addresses that lack of information in an exceptional manner, through detailed biomechanical analysis of the world's best sprint and hurdle athletes, with data collected in situ at the 2018 IAAF World Indoor Championships, held in Birmingham, UK. High speed videos (150 Hz) were compared for eight sprinters and seven hurdlers for the start and initial acceleration phase of the finals of the men's 60 m and 60 m hurdles. Temporal and kinematic data were supplemented by vector coding analysis to investigate mechanisms by which these world-class athletes translate their centres of mass (CM) up to the fourth touchdown post-block exit. The sprinters and hurdlers coordinated their lower limb and trunk movement in a similar manner throughout the start and initial acceleration phases, which contributes new conceptual understanding of the mechanisms that underpin start and initial acceleration performance. Differences between groups were initiated from block set-up, with the hurdlers utilising a larger block spacing, but with the front block nearer to the start line than sprinters. Even after accounting for stature, the biggest differences in the raising of the CM occurred during the block phase, with hurdlers greater than sprinters (difference in vertical CM displacement scaled to stature = −0.037, very large effect size). Subsequent flight phases showed the biggest differences in the translation of the CM, in part due to longer flight times in the hurdlers, whilst the techniques of the two groups generally converged during the ground contact phases of initial acceleration. In highlighting that similar techniques are used by world-class sprinters and hurdlers, despite differing task constraints, this study has provided invaluable insights for scientists, coaches, and athletes, that will inform further developments in understanding and practice across both sprints and hurdles.
Highlights
It is well-established that effective maximal sprint acceleration is dependent on primarily horizontal external kinetics (Morin et al, 2011; Rabita et al, 2015) and matching segmental kinematics (Kugler and Janshen, 2010; Nagahara et al, 2014; von Lieres und Wilkau et al, 2018), research has not examined what effect the inclusion of a high hurdle has on acceleration performance and centre of mass (CM) projection
Visual inspection of whole body positions adopted by the two groups at key events (Figure 4) showed differences in block spacings and thigh angles at first movement, but otherwise similar patterns were observed at block exit events
With the exception of contact time for ground contacts two and four, all contact and flight times were longer in the hurdlers
Summary
It is well-established that effective maximal sprint acceleration is dependent on primarily horizontal external kinetics (Morin et al, 2011; Rabita et al, 2015) and matching segmental kinematics (Kugler and Janshen, 2010; Nagahara et al, 2014; von Lieres und Wilkau et al, 2018), research has not examined what effect the inclusion of a high hurdle has on acceleration performance and centre of mass (CM) projection. The placement of a 1.067 m high hurdle 13.72 m from the start line introduces an additional task constraint. This is yet to be investigated in terms of its effect on performance in the start and initial acceleration phase, which are critical to optimal overall performance. The absence of an examination of initial acceleration mechanics in high hurdles and a detailed comparison of sprint and hurdle start and initial acceleration has important implications for both coach and athlete development as well as the understanding of optimal performance
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