“Researchers at Southwest Minnesota State University reported in the May 2009 issue of The Journal of Strength and Conditioning Research that using elastic bands in addition to the weight may increase your one-rep max for your bench press. Here’s how you can try it for yourself: Tie each end of an elastic band around a barbell (outside of where you’ll have your hands for the lift) and lie faceup on the bench, slipping the band under your back, underneath your armpits. Lift the bar from the supports and perform the list as usual, being sure that you have a spotter throughout.
Source- The Body Shoppe: Training. Muscle and Performance Mag, December 2009.