From drive to max velocity across 100 meters
A sprint is usually divided into the drive phase, a transition, and a max-velocity phase. Out of the blocks the sprinter is in a forward lean with a low projection angle, pushing the ground backward over relatively long ground contacts to accelerate. As speed builds the body gradually rises toward an upright posture, stride length and frequency increase, and ground contact times shorten dramatically.
By the max-velocity phase contact times can fall to around a tenth of a second, so force has to be applied very quickly. This is why elite sprinting is described as a problem of force applied in a short time rather than simply how much force a runner can produce.
What changes phase to phase
The shift from acceleration to top speed is gradual, not a switch. Posture rises, the foot strikes closer to under the hips rather than far ahead, and the emphasis moves from pushing the ground horizontally to applying large vertical forces in a brief contact. Most sprinters reach top speed somewhere in the middle of a 100 meters and then work to decelerate as little as possible.
Exact phase lengths differ by athlete, event, and level, so the diagram shows a general pattern rather than fixed distances.