A sprinter does not run the whole race at maximum speed. Acceleration occupies most of the first half, and the finish is a contest of who slows least.
Acceleration is a long process
Leaving the blocks, a sprinter is stationary and must overcome inertia with each stride, which is why the first steps are short and driven forward rather than upward.
Speed builds progressively as the body rises from the drive position toward an upright running posture, and that transition takes a substantial part of the race.
Top speed is typically reached somewhere past the midpoint, which means the majority of a short sprint is spent getting up to pace rather than holding it.
Why maximum speed cannot be held
Running at peak velocity draws on stored energy in the muscle that is available instantly and depletes within seconds of maximal effort.
As that supply falls, force production per stride declines, and the runner loses ground contact quality before any visible change in technique appears.
Everyone in the field decelerates over the closing metres, so the race is decided by the size of that decline rather than by anyone accelerating late.
What the start actually contributes
Reaction time is a small fraction of the total, and the difference between the quickest and slowest reactions in a field is a fraction of the winning margin.
What matters more is the first few strides, where block setup and body angle determine how efficiently force is directed backward against the track.
A poor start can be recovered from, but only by spending energy earlier, which shortens the phase at top speed and costs more at the finish.
Longer sprints change the shape
Over two hundred metres the acceleration phase occupies a smaller share of the race, so managing the deceleration becomes the dominant skill.
The bend adds a further constraint, since running a curve requires lateral force that is not contributing to forward speed at all.
Runners therefore learn to relax through the middle portion, which sounds counterintuitive but reduces the rate at which the energy supply is consumed.
How training reflects this
Sprint programmes separate acceleration work from maximum-velocity work, because the two use different body positions and different muscular demands.
Short repetitions with long rests develop peak speed, since the point is to reach maximum output rather than to accumulate fatigue.
Speed endurance work targets the decline instead, extending how long a runner can hold near-peak output rather than raising the peak itself.
