The original motivation to create the bench press shirt was to create a stiff and supportive shirt to reduce the risk of injury. Bench shirts can be made from a multitude of materials including: canvas, denim, polyester. They come in single-ply and multi-ply, with extreme compression they support the deltoid and pectoral muscles to handle extreme weights. The single-ply, as the name infers is one ply of material, the multi-ply offering multiple layers of material. Most single-ply shirts have a closed back, and most multi-ply shirts have an open back; however there are nuances to this and the legality will range from federation to federation. The shirt is no replacement for strength, they allow the lifter to maximize their technique to a much higher degree than raw. As the weight is lowered, the shirt stores energy, which is then released when the lifter pushes the weight up. Make no mistake, mastery of these shirts is extremely difficult and can take a very long time, but the used properly can be a work of art and give your CNS new adaptations that are unachievable lifting raw.