The weight lifting belt is designed to protect the lumbar region of the spine while lifting extremely heavy weights. Often used in exercises such as squats and deadlifts, it performs this protective task by pushing the abdominals and core muscles in toward the spine, therefore creating a wall of muscle that helps maintain proper lifting form and in turn, keeps the back from hyper extending which may cause serious injury.
Studies have shown that another potential benefit of the weight lifting belt aside from support and injury prevention is that those who wear a belt during heavy load exercises can reduce spinal shrinkage. A study performed showed that those who wore a belt lost 2.87mm of height vs. those that didn't who experienced a height loss of 3.59mm. 1
Weight lifting belts should not be relied on too heavily save for very heavy lifting and competitions. When relied on too often, the weight lifting belt may cause the abdominals and core muscles to become underdeveloped due to the assistance offered from the belt. Proper form and technique should always be used; a weight lifting belt is not an excuse to break form. When opting to max out on exercises like deadlifts or squats, it is recommended to use a weight lifting belt.
The lifting belt should be securely positioned above the hips (or partially on the hips depending on the size of the belt) with the rear portion across the small of the back. Some belts have a much larger area in the rear that allow for a very strict and controlled movement. If the front of the belt is falling down onto the thighs while lifting, one should double check their form and make sure the back is kept straight and properly aligned while performing the exercise.
1 Effect of a weightlifting belt on spinal shrinkage - N D Bourne and T Reilly
Centre for Sport and Exercise Sciences, School of Health Sciences, Liverpool Polytechnic, UK