My nephew, Brian, is a big and fast football player. Well, he played football in college and is now in training for a pro day (NFL and other league coaches gather to watch players go through their paces) at the end of March.
He told me that at the training center he is using, they have special treadmills that can go up to 26 miles per hour (and support lots and lots of weight).
At the start of his training session, they had him do 8 second, 14 MPH sprints. We talked just the other day and he told that he had just managed to finish a 6 second sprint at 21 MPH.
Twenty-one miles per hour....and we are not talking about a lean, stringy human here. We are talking about over 250 pounds of muscle and bone, moving in a highly coordinated fashion; every motion, every muscle use has go to be optimized....
That is amazing. Go, Brian, go!