Arching in the bench press is not cheating. It is good technique. There is more to arching than just trying to lift more weight. In any bench press variation, whether it is flat, incline, or overhead, arching positions your pecs in a more effective length and alignment to produce force. That means more tension in the muscle and better potential for hypertrophy. It also puts your shoulder blades in a stronger and safer position, giving you better joint support and reducing the risk of injury. So

You SHOULD arch when you do a bench press. Even if your goal is the build the muscle. Of course the degree of arch should be different with a bodybuilding bench press compared to a powerlifting bench press, but arching your back, especially your upper back is what you SHOULD be doing if you want to build pecs. Arching protects your shoulders. Arching increases pec activation If you’re a powerlifter, arching a little bit harder decreases the range of motion which allows you to press more in compe