Abstract
This study investigated the influence of the intention to lean the body forward on spatiotemporal and ground reaction force variables during the acceleration phase of a sprint. Fourteen active adults performed two 50 m sprints (with and without the intention to lean), during which spatiotemporal variables and impulses were obtained using a long force platform system. Effect size (Cohen’s d) was used to examine the differences between the two trials. We found that running speed and net anteroposterior impulse did not change by the intention for all steps. However, step frequency increased in the initial two steps through decreases in support time and flight time by the intention. Moreover, these shorter support and flight times were caused by a decrease in the vertical impulse. The propulsive impulse did not change during the initial part of acceleration phase, but the braking impulse decreased at the first step. This study demonstrates that an intention to lean the body forward leads to a smaller braking impulse and a higher step frequency through shorter support and flight times and a smaller vertical impulse during the initial part of the acceleration phase of a sprint.
Highlights
Sprinting is an essential ability in many sports and is a basic exercise in a physical education class
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FTat at the the initial initial five toto ninth steps increased through the the intention. These results demonstrate that theintention intentiontotochange changebody body posture posture may may result intention. These results demonstrate that the result in in aa change changeininlocomotor locomotorpattern patternwithout withoutproducing producingaachange changeininrunning runningspeed
Summary
Sprinting is an essential ability in many sports and is a basic exercise in a physical education class. To accelerate to a high maximal speed, sprinters theoretically need to produce a substantial positive net anteroposterior ground reaction force (GRF) during the support phase of each step. Kugler and Janshen [9] found that faster athletes produce a smaller resultant force compared to slower athletes, but the GRF vector of the faster athletes is directed more horizontally than that of slower athletes. The direction of the GRF is more important than its magnitude for effective acceleration This concept has been confirmed in recent studies [8,10,11,12], and to direct the GRF vector more horizontally is one of the key instructions for improving sprint acceleration performance from a practical perspective
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