China Guy - they’re SIX? Seriously? When the hell did that happen? God, I think this means I’m getting old.
Yep, almost six and a half actually. And turning into quite the Americans, but both still speak Chinese. Almost unbelieveable though how much progress Serena has made the past 9 months in the US, and it started literally the first week we were here. She’s got a LONG ways to go but every day is progress even if she’s getting outrun by her sister.
Never happened when the kids were of reasonable age, over 8. Never happened at all with the older one. The younger one sometimes lost it when quite young. I have fast reflexes - I caught her arm and then just held her immobile until she settled down - usually in tears. It then turned into talking and hugging.
While my daughter is too young to “hit” (she does pop me in the face on a regular basis in the course of her frequent unscheduled “unfocused infant flailing!” times), with my younger cousins-once-removed I’ve tended to prefer the following:
For young children–a stern no, and then gently preventing them (by blocking or holding their wrist) from doing it again until they get distracted.
For older children/preteens–again with the stern no, and a timeout/sending them to their room, or other punishment that implies they’re acting like a toddler.
For teenagers–a brief lecture on the pitfalls of a “might makes right” society, delivered while/after wrestling them to the floor and sitting on them. (this is one of those 6-0-250 behaviors, in that if I wasn’t 6’0" and 250lbs I’d not get away with it as often.)
Of course it depends on the child and the reason. My oldest (22) I can’t even imagine hitting me for any reason other than playfulness. We have raging tickle fights occasionally and I KNOW she has some upper body strength because of the way she flails them about as she runs away. 
Her younger sister has special needs; borderline autism spectrum, sensory processing disorder and mixed expressive-receptive language disorder. She gets really frustrated sometimes and while she’s never come out and hit me, I can see it happening and my reaction will depend on the circumstance. It will never ever include hitting her back. She has kicked at me when trying to resist me holding her hand, which she loathes. She is very affectionate but she needs to initiate or it makes her skin just crawl. If I ask her to hold my hand she’s usually okay with it for brief periods like crossing the street, but if I just grab her hand she will protest. I can’t really punish her for something out of her control, but she knows she will be forced to hold my hand whether she fights it or not so she’ll usually remember to grab mine first. If I made a big deal and punished her for something like that it wouldn’t be productive at all.