You can't move quickly with massive muscles, big musculature is about instantaneous power - look at endurance runners, how many of them have a physique like The Flash, http://covers.cbrd.info/02983f42a0e5967b8997b606646eeac7_xl.....

Batman couldn't even run with calf muscles this big his legs would bang together - http://img2.wikia.nocookie.net/__cb20060923231859/marvel_dc/....

Looking at the DC Comics website none of it seems to be suitable for children.