This is interesting. The first creatures we know of that had high 'warm-blooded' metabolisms were the dinosaurs. And the dinosaurs were the first group of creatures that started using bipedalism. (Not all, of course, not the slow browsers.) Perhaps they became two-legged because once you have so much muscle power that you start rearing up when you try to rush, you might as well go with it and put all the power into the legs that stay on the ground.
It'd also explain why cheetahs have non-retracting claws: those claws aren't primarily for attack, they're for extra grip.
(If I recall correctly, a good sprinter can beat a racehorse off the line - just not over the first furlong.)