Let's bring some science into this as there is going to be a lot of varied opinion. Various quotations from the Godfather of spinal mechanics, Stuart McGill.
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"Those who have never had a previous back injury appear to have no additional protective benefit from wearing a belt.
• Those who are injured while wearing a belt seem to risk a more severe injury.
• Belts appear to give people the perception they can lift more and may in fact enable them to lift more.
• Belts appear to increase intra-abdominal pressure and blood pressure.
• Belts appear to change the lifting styles of some people to either decrease the loads on the spine or increase the loads on the spine.
There is no question that belts assist in generating a few more Newton-meters (or foot-pounds) of torque in the torso through elastic recoil of a bent torso that is stiffened with a belt. However, if a neutral spine is preserved throughout the lift this effect is diminished. In other words, to obtain the maximal effect from a belt, the lifter must lift poorly and in a way that exposed the back to a much higher risk of injury!
Evidence suggests that people change their motor patterns, together with their motion patterns when using a belt. The evidence suggests that these motor control changes can elevate the risk of injury should a belt not be worn in a belttraining athlete."
Source:
http://www.nsca-lift.org/hottopic/do...s - v3.pdf