Have used hip/harness belts, probably much wider than the one in the picture, a few times. Used also for dips & chins.
When first using one years ago , was surprise how fast the ability was to add on weight from workout to workout. Reps shot up to 20 or 30+ before I knew it, even with increased added plates. .
I usually put a towel near the lower abs/groin because of the pressure and rub the chain/belt may cause the more weight I used. If leaning somewhat forward like the guy in the video and doing short ROM, than probably not that much pressure against the body. Actually fun workouts after a while. I found that the wider the belt, the easier a heavier weight is to handle...doesn't tend to dig into the body that much.
Usually I straddle two raised platforms/boxes, letting the chain/weights hang in the middle and squatted that way...can go down lower that way. Sometimes directly from the gym floor...depends. I have done belt squats in a rack, finding the balance point with two chains together attached to the rings in the belt. .
Good luck.
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