Are belted squats acceptable when rehabbing a back injury?
Depends. What’s the injury? How far are you into the rehab process?
Simple answer- almost certainly not. The belt isn’t going to protect you. Any spinal loading is likely to put your back injury at greater risk.
If you’re asking if ‘belt squats’ are safe, it depends on your injury and how proficient you are at the movement, your build and of course the goal. This is really a personally specific question and I’d need to see you squat, your MRI and what causes you pain. etc.
The biggest approach is to get out of pain before you train again. All of this training around back pain nonsense that I’m seeing is quite misleading.
If the former (Dan addressed this) then I would not.
Hope this helps!