MUSCLES ENGAGED Chest Strengthening the chest muscles will help you push things easily and effortlessly. The muscles in your chest help stabilize your shoulder joint, which reduces your vulnerability shoulder joint injuries. Working your chest muscles also has an aesthetic factor (body contouring). Shoulders The shoulder is the most movable joint in the body. However, it is an unstable joint because of the range of motion allowed. This instability increases the likelihood of joint injury, often leading to a degenerative process in which tissues break down and no longer function well. Exercise Instructions Step 1 Start in a push-up position with your hands right beneath your shoulders and your back flat. Step 2 As you descend into the push-up, pull your knee up to your elbow. Step 3 As you press out of the push-up, return your leg back to the starting position and repeat on the other side.