Wait ... Are you not supposed to suck in air and push your stomach out while you squat?
Great timing. I'm about to go to the gym right now.
Breathing in and bracing (creating abdominal pressure) is a good thing. It's very structurally stable. Think of a pressurized can versus a can with a hole in it. Which one can stand more weight on it?
And it's not why jacked guys have stomachs that poke out. That's because of the type of steroids they're taking.
I brace on squat, bench, deads, planks, back lever, anything I can. My stomach doesn't jut out when I'm relaxed.
The purpose of a belt is not safety related. It's to be able to create more pressure.
Being punched is not the same as holding weight. And creating stability.
If bracing is such a bad idea... why do strongmen and powerlifters do it? They're smart, they're strong..
Perhaps the way you think of bracing is a little misunderstood. When I brace, I take a deep breath and push as many of the muscles as I can outward. This also contracts them because well.. they can't move if they're not contracted. So this creates a tight wall around a bunch of air that's trying to expand - stiffness. If there was no air there... the muscles can't contract as hard as they could if it were because there's nothing to push against.
Breathe deep. Try to engage as many muscles and feel pressure all the way around your mid-section. Squat.