User blog:U.V.I.R/All Might on steroids?

Me and my friend were talking yesterday, and we thought of something. How and why does All Might change his body into a more muscluar form when using One for All? I mean, he told Deku that he should strengthen his body so it could handle it, and when Deku uses One for All he just uses his body, not change into another form. So why does All Might, and how?

Also when Deku was feeling down, All Might had told him that he too was quirkless. So what is it? Does he have a secret quirk? My friend and I's theory is that HE IS ON STEROIDS, but that was mostly a joke.... or was it?

Comment your theories.