User blog comment:Guts!/Anime Depiction of Luffy's Gear Second/@comment-972068-20130528014001/@comment-972068-20130529020147

Everything in the Wiki has a source. It must have a source or else it's simply incorrect, floating information. If the Wiki makes up information, that's bad. Since we're discussing an element from the series, we should only look at evidence from the series itself and see what we can conclude.

By the way Guts, Luffy's training was mostly for Haki, not Gear Second. Also, again, his entire body.

We can also look at evidence from science in general. I could be wrong, but I'm fairly certain it's physically impossible for your blood rate to increase in one area specifically. It's pretty much a constant thing throughout. So, scientifically, the claim "Luffy can activate in one particular area" is completely false.