this is OTT sorta, because it's a soccer kicking question. the same principle should still work in MA.
to kick a ball harder for a shot, if you extend your other arm out kind of diagonal and up, it helps a lot. so if I want to kick with my right foot, I stick my left arm out. then as your right leg comes forward, your left arm comes in. makes sense right? like left jab sets up right cross for power.
now ... I just watched some video that added to that. so let's say your left thumb is pointing in toward your body. if you rotate your arm so that your left thumb now points out, so your palm would be face up, then kick, that makes it even easier to add a little more power. I tried it out and anecdotally, yup. the extra little rotation, kind of wind up, then unwind, makes it all a little easier/better. I'm sure there are many more details when, say, a pitcher pitches a baseball.
my question: how does this work?
TL;DR: twist left arm outward, helps your right kick add power. how?