Pullups are normally reffering to your hands being in a pronated position whereas chinups your hands are in a supinated position. Check them out in the muscle exercise directory for form and muscles involved etc.
If you check out the ExRx directory, this is not at all how they are defined.
Chin http://www.exrx.net/WeightExercises/Lat ... hinup.html
Pull http://www.exrx.net/WeightExercises/Lat ... ullup.html
Both use pronated grips.
I personally do not like this chin=sup and pull=pro classification. They should all be called pull ups (since they all involve us pulling ourself up) and chin should be if the chin's over the bar. Supinated's usually the easiest way to get the chin over the bar, yeah, but a lot of people don't manage to do that, and many manage to do it with prone, so we should call it sup-up or pro-up to describe pull ups using specific grips. Neut-up or hammer-up for the palms-facing-each-other kind.
I'd really like to understand how ExRx distinguishes between chins and pulls though, because looking at the animations they use, they seem incredibly similar:
In pull-up description: "Pull body up until neck reaches height of hands." How to understand "until neck reaches height of hands"? Need reach "neck begin" (chin) or "neck end"?
Honestly, I call these neck-ups. Chin-up should just mean touching the chin to the bottom of the bar. Reason being, we call the fullest RoM a sternum-up or chest-up but clearly that's only touching the bottom, not the top.
i rarely support extremists but in this case i'll make an exception. i'll 2nd for pull is overhand, chin is underhand.
I oppose, naming something "chin" based on forearm rotation is not logical etymology.
I know this book I reviewed here viewtopic.php?f=25&t=8000
calls it a 'chin up' with a prone grip and a "reverse chin up" when using a supine grip.
People like to try and pretend there is consensus, but there isn't, and this shouldn't be something we decide democratically either.