[NorthStrong]

It's important to consider that sprinting is the highest velocity / stress that the human body can achieve. So if any world class sprinter tried to run an all out sprint, their training for the next week or so would be down, simply due to the fatigue induced by that sprint.

That same principal applies to all sports, and is why people train using both specific and general means, as well as training submaximally for the most part.

A marathoner does not run marathons to get better at them, they run portions of the race, work on running technique, etc. A 100m sprinter will run tempo runs, 40m sprints, etc.

Charlie Francis has a lot of great information on this topic, as he is / was the best sprint coach in the world really.

An interesting anecdote is that Ben Johnson used to be able to squat 600x5 (i believe that's the right amount of reps). He was pretty damn strong and fast.

Because fast is a product of strong, and strong is a product of big. That is why sprinters are jacked. They're jacked to facilitate their ability to be strong, which enables their speed to happen. (more or less)