Caporegime
sprinting - known to be a great mass builder (look at the professional sprinters, large muscles are the result of explosive sprinting.)
dont be so naive. the type of sprinters that can get away without doing weights, and be like a world class sprinter, are sprinters that are world class (and then its only a few of them).
the majority will not be genetically gifted enough and WILL do weights.
Another thing to remember, sprinters arent that big really, they just look 'big' due to being completely cut.