joking as side wanna improve the power of your punch a good punch comes from the legs so when your gonna through one bend you knees slightly and spring you torso forward as you throw the punch the power comes up from you the legs especially the one you have placed to the rear also good deltoids improve the punch sorry but biceps have nothing to do with extending your arm as you do when throwing a punch if anything you wanna work on your triceps helping to snap your arm out quicker.
