I would wear one at about 85% of my max. I like to wear it only on the heavy sets. Warmups I do without. Here’s an example, if you dead 400, you might want to think of it at about 350. Why? form can break down for anyone on the heavy weights or on high reps. That’s when it would help you out. Easy sets I would go without. Don’t overthink this. The Paul chek articles aregood, but i really don’t feel they apply to the competitive lifter. I’ve never "tried to activate " my ta. I personally think it’s a waste of time that causes the average person to buckle over. I woul try to draw my upper body towards my hips. That would provide plenty of stability for a heavy squat and dead without visualizing your stomach drawing in. At the heavier sets I put it on for some additional.