At what point does a lifting belt stop being costume and start doing something?

It is a tool with a specific job, and the confusion in your gym comes from almost nobody stating what the job is.

A belt gives your abdominal wall something to push against. When you take a breath and brace, you are pressurising your midsection, and that pressure is what makes your torso rigid. A belt does not hold you up and it is not a back support in the sense of a brace — it is a surface for you to expand into, which lets you generate more pressure than you can against air alone.

Everything follows from that, including why both camps sound right:

If you cannot brace, a belt does very little. There is nothing to push against a wall you were never pushing on. That is the honest core of the "learn to brace first" argument, and it is not gatekeeping.

If you can brace, it adds to something real. That is the other camp, and they are also right, they are just further along.

So the question is not your squat number, it is whether you already know what bracing feels like. A quick self-test: at the bottom of a heavy set, can you feel your midsection pushing out in all directions — front, sides and back — rather than just sucking in and holding your breath? If yes, a belt has something to work with. If you are not sure, that is the thing to spend a month on, and it is free.

The honest summary: a belt is a multiplier on a skill. Multiplying zero still gives you zero, and multiplying something gives you a bit more of it.

From watching a lot of people go through this, the three mistakes arrive in a predictable order and none of them is buying one too early.

Wearing it for everything. Warm-ups are where bracing gets practised, and a belt on a warm-up set removes the practice while giving you nothing back. Belt the sets that are actually hard.

Cinching it so tight you cannot breathe into it. People assume tighter equals more support and it inverts the mechanism — you need room to expand into it. Tight enough that you notice it strongly when you brace, loose enough that a full belly breath still happens.

Treating it as permission. This is the one that actually causes trouble. A belt makes a heavier weight feel more manageable, so the temptation is to add load faster than your positions can hold. The rounding you were fighting at 90 arrives again at 110, and now there is more weight on it. Progress at the same rate you were, and let the belt improve the quality of the reps rather than the size of the jumps.

One thing worth adding: it is a training tool, not a medical device, and it does not make an unsafe position safe. If something in your back is complaining, that is a conversation for somebody who can actually look at you, not a purchase.

What actually changed for me, since you asked for specifics rather than theory.

I bought one at roughly your position — squat in the nineties, moving but grinding. The week after, the honest effects:

• Top sets felt tighter, not stronger. No sudden jump in what I could lift. What changed was that the last two reps stopped feeling like my torso was folding slightly before my legs gave out.
• My warm-ups got worse for a fortnight, because I wore it for everything and lost some of the bracing I had built. That was my fault and it is the failure mode the sceptics are describing. I now put it on for the top one or two sets and nothing else, which is the setup I would have started with if anybody had said so.
• Position held better across a set of five than a set of two. The benefit showed up in fatigue, not in maximum effort, which surprised me.

On buying: get a belt of even width all the way round rather than one that tapers narrow at the front. You are pushing into it at the front as much as anywhere, and a tapered one gives you less there — which is exactly backwards for the mechanism above. Beyond that, prong or lever is preference; the lever is faster between sets and a nuisance if you want to change the tightness for different lifts.

And it should be much tighter than a normal belt but you must still be able to take a full breath into your belly. If you cannot, it is too tight and you have removed the thing you bought it for.