Put on the belt and pull it as limited as you can. It should not be decrease. If it is decrease, no problem, just go down one inches or two more and punch an extra couple prong gaps. When you have the Rubber Timing Belt on limited, suck in some air and force out your stomach as difficult as you can. This builds up what is known as intra-abdominal stress. The belt is useless if you basically band it on without intra-abdominal stress.
Belts Help with Intra-Abdominal Pressure (IAP)
There have been countless studies done on intra-abdominal stress with a lifting belt. Some facts about IAP:
1) Spinal Loading is reduced.
2) The AIP allows to stiffen the trunk contributing to stabilization. This will seem to improve a lifter's explosive energy without compromising the joint mobility.
3) When doing large squats it has been noticed that there is spinal shrinkage with pain but only when a belt is NOT used.
4) Weightlifting shoulder straps help to minimize trunk rotation. Trunk rotation is the cause of many twisting kinds of returning accidents.
Again, to use a belt effectively, pull it very limited then inhale and force out your stomach as far as you can against the belt. Keep the returning arched returning while performing an improvement. As for breathing during the raise, it is perhaps best to not keep your breath. If you take in a deep breath slowly for Automotive Driving Belt purpose of holding it to build up AIP, you are doing what is known as the Valsalva Move.