MUSCLES ENGAGED 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. Quadriceps The quadriceps (quads) are a group of four muscles on the front of the thigh. They allow your knee to straighten and provide stability when standing. Your quads are the most important muscle group for maintaining the ability to stand and to walk independently. Equipment Used Barbell A barbell is a piece of exercise equipment used in weight training, weightlifting and powerlifting. Barbells range in length from 4 feet (1.2 m) to 8 feet (2.4 m) and vary in diameter. Exercise Instructions Step 1 Start in a wide squat position with your shoulders back while holding the barbell in one hand over top of your shoulder. Step 2 Squat down, leading with your tailbone making sure to keep your lower back flat at the bottom of the range of motion. Step 3 Stand back up pushing through your heels and press the barbell up until your arm is fully extended. Return the barbell to the starting position and repeat.