Sprinting is great, what was you program like?
Well I was just starting out.
There are some tennis courts by my house, so id do a dynamic warmup ( some lunges on the court,squats,squat jumps and some joint mobility drills ) then id start sprinting.
The court is about 30 yards, so the first week i did 3 sprints 2x a week, then every 2 weeks i bumped it up one sprint.
I was @ 5 sprints 2x a week before i got put on the disabled list......I was getting lean too