Back belt benefits
Reduce pressure on the spine
Some studies have confirmed that wearing a belt while lifting weights increases intra-abdominal pressure by up to 40 percent, while one study reported that intervertebral disc pressure decreased by 50 percent. Increased intra-abdominal pressure is similar to inflating a balloon inside the abdominal cavity. The pressure within the abdominal cavity pushes the spine to support it from the inside, while the core muscles in the abdominal wall and lower back press on the spine from the outside. This internal and external pressure stabilizes the spine and reduces the pressure the spine receives when lifting heavy weights. This is how lifting belts can help protect against back injuries while lifting. Not because of the belt that provides support, but because of the way the body interacts with the belt that provides support for the spine.
Belts create better body biomechanics
Research shows that when lifting weights, wearing a lifting belt reduces the amount of spinal flexion (forward curvature of the spine), spinal extension (backward curvature of the spine), and lateral flexion of the spine (turning from side to side), but increases the amount of Flexion in the hips and knees. In other words, the belt forces you to raise your legs more than your back, which is exactly the biomechanical position you want to use when lifting something off the ground. These are also the biomechanics you want to use while squatting with a barbell.
How do I wear it?
When wearing the belt, it must be properly positioned and tightened. Oftentimes I've seen lifters move the belt to a more comfortable position under their bowels, although this goes against what they have learned about belt use. Obviously, the belt should not be too loose, although many make the mistake of making it too tight. A belt that is too tight to tighten your abdominal wall will work properly against you. Take a breath (hold it), put the belt in place and brace the abdominal wall. Draw the belt tight enough to restrict the position of the slightly supported abdomen for maximum benefit.