We have great flat bench gym for sale, with options that will suit any gym. Good technique is important to any workout, and our comfortable flat benches help users work out to the best of their ability while doing a wide variety of exercises. A flat weight lifting bench is going to get used a lot in busy gyms for all kinds of free weight dumbell exercises, so get a good one that will last a long time. It is the staple exercise for building muscle mass and strength in the chest. The primary muscles that are worked in a bench press are the triceps brachii and pectoralis major with the anterior (front) deltoids, traps & back as secondary muscles used in the flat barbell bench press. It is the staple exercise for building muscle mass and strength in the chest. The primary muscles that are worked in a bench press are the triceps brachii and pectoralis major with the anterior (front) deltoids, traps & back as secondary muscles used in the flat barbell bench press.