MUSCLES ENGAGED Triceps Triceps are an often forgotten muscle group. Triceps are located on the opposite side of the biceps at the back of the upper arm. Well strengthened and defined triceps make the arm look bigger and sleeker (reducing the "flabby arm" look). 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 Place your hands beside you on the bench with your feet placed out in front of you. Step 2 Keeping your back straight and your tailbone close to the bench, lower yourself until your arms are at a 90 degree. Step 3 Raise yourself back up to the starting position by fully extending your arms and contracting your tricep muscles. Repeat action.