MUSCLES ENGAGED 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. 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 Kneel down on one knee with your other leg out in front of you just past 90 degrees. Step 2 Keep your back straight and your hands at your side as you slowly push forward and stretch the hip flexors open. Step 3 Gently pull back to the starting position and then push forward again for 5-10 pulses.