I was thinking about it in the context of sports, where you do a lot of short sprints broken up by lighter movement. 

There's a difference between fast run and Sprint. 

I see a Sprint as a 90% or greater effort.

Like you're really trying to hit top speed not just run at a good pace. 

Maybe you could do it once but you won't be able to keep that pace up for a mile.

ProofOfWorkFitness

But what if you sprinted like 50m and then jogged 100m? Could you launch right into another 50m sprint?