There are two types of breathers. Belly breathers that breath intto their abdomen, and chest breathers that breath into their chest. Chest breathers are by far the most prevalent and belly breathers are supposedly uncommon, although I think the numbers are higher then realized.
I am a belly breather--always have been, never tried to make it happen. From a health standpoint it is supposed to be extremely beneficial. From a high rep squat standpoint--it is hell. When I used to do high rep squats exclusively I kind of taught myself how to chest breath while squatting. let me tell you, it isn't like riding a bike, you (I anyway) forget how.
When I realized I hit a wall on deads and wasn't going to rack pull 590 x 10 as planned I decided to do high rep safety bar squats off a box. My goal was 315 x 30. I kept my belt one notch looser so I could breath better. Not wearing a belt is not an option for me as I have herniated disks, and a herniated belly button--both sides fucked
I did continuous reps until 20 taking LITTLE TINY breaths, at 20 I stopped and tried to rest pause, I forgot how to chest breath so I was breathing into the belt which got me very, very little oxygen when I needed a LOT. After about 20 seconds of this foolishness I buckled down and did 5 more reps, my legs were not done, but the oxygen debt was suffocating. I missed putting the bar in the saddles and almost had a BIG accident because I was so out of breath.
I racked it, hit the stop watch and waited 90 seconds and banged out 15 reps and missed the saddles again.
Moral of story, if you are doing high rep squats and are a belly breather and can get by without the belt, don't use it. If you need it, don't be afraid to rack the weight, get some oxygen debt settled and go on. The key is stimulating growth, not BB orthodoxy.
IA