User blog comment:Pacifista15/Seriously, Luffy?/@comment-3202520-20111123075930/@comment-3986064-20111123134104

Just that elephant Gatling is enough to drive a man to exhaustion, it was not the wound. It was Luffy's body not being able to handle that much awesomeness just as it always happened. After he defeats his enemy, he collapses. Same as with Arlong, Croc, Enel(I'm not very sure here), Lucci, Moriah and after the WB war sent in a coma by Ace's death(Akainu). So ofc he has to has to collapse after beating Hody.