User blog comment:12th Supernova/Chapter 784: Spring Theory/@comment-5239749-20150423224108/@comment-130.43.25.188-20150425080751

muscle control sounds right.but i vote for observation haki.he locks his fist to the target(doflamingo ) through observation haki.

changing the jab to a hook isnt that hard.the goal to throw a hook from the start just make look like a jab. and its always more efective after a series of heavy jabs so the opponent focuses the defence to the front.

try faking a low kick  to  a hammer kick.

or the brazilian kick.

as for bellamy showing up that wasnt bad.the onepiece world is more than just the mugiwaras.all characters evolve in some way.its nice to see that.