Load your muscles eccentrically by gently lowering the bar to your chest. The muscles in your body must operate both concentrically and eccentrically as you lower and push the barbell during the bench press. Concentric muscle contraction occurs when you lift the weight straight up, while eccentric muscle contraction occurs when you lower the weight below your chest. Lifting weights requires both types of contractions. When you bench press, you are working both your upper and lower arms muscles. The triceps on your upper arm and the deltoids on your shoulder are the two largest muscles in your upper arm. The pecs, rhomboids, and middle delts are the main muscles in your chest. Your triceps are also involved in pulling down weights during the bench press. While keeping your elbows tight against your sides, squeeze the bar hard enough so that your triceps touch it at the top of your movement. To effectively work all the muscles you need to during a bench press, you have to be able to lower the barbell below your chest. This allows the muscles of your back to be involved in the exercise. When you lower the bar too high, you risk straining or tearing these muscles. Lowered bars require more effort from your leg muscles since you can't use momentum to help you lift heavy weights.