I think this is one of the biggest things amateur athletes ignore in their training. It is so obvious if you simply look at olympic sprinters VS. olympic distance runners. Sprinters have monstrous legs due to strength training and distance runners have twigs for legs, because there training involves only running for miles and miles.
Sprinters have to focus a good majority of their training on weight lifting to build up their fast twitch muscles in their legs. Fast twitch fibers can be further categorized into Type IIa and Type IIb fibers. Both these types of fast twitch muscle fibers are imperative to strengthen for any sprinter. And they can only become stronger by lifting heavy weights.