Slow motion sprints are great learning tools.
Young runners, pay attention to his contact and contact time. The ball of his foot (NOT toe or heel) touches directly below his body in a loaded position, ready to deliver force to the ground. DIRECTLY BELOW even though it looks as if he is reaching. This is at top speed, you are not seeing the start, which in almost all other sports is the more important part. But watch the contact of the foot w/ the leg drive that he uses to propel himself fwd.
REACHING actually causes a runner to slow down. They are stopping themselves little by little with each step, they are wasting energy and they end up w/ extra contact time w/ the ground mostly b/c it takes them a long time to get the foot back to directly underneath the body where it can deliver force to the ground again. Ultimately wasting their speed talents.