User blog comment:Almerzskie/chapter 601,.Luffy's new technique?gear 2 with a new style?/@comment-3079795-20101026045215

we haven't seen gear third yet but this is what I hypothesized. That Luffy can somehow use Busōshoku Haki within his bones to make them stretch and essentially put himself into his gear third form. This way when he exits gear third he won't need to blow all the air out of his bones, making him smaller.