Interesting that you request more sources from me (even though I provide 1 from a reputable jounal), but you don't post your own. Not that I would even try call you out. Very well:
Kingma, I; Faber, GS; Suwarganda, EK; et al.
Effect of a stiff lifting belt on spine compression during lifting
SPINE, 31 (22): E833-E839 OCT 15 2006
Ivancic, PC; Cholewicki, J; Radebold, A
Effects of the abdominal belt on muscle-generated spinal stability and L4/L5 joint compression force
ERGONOMICS, 45 (7): 501-513 JUN 2002