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. Equipment Used Medicine Ball A medicine ball (also known as an exercise ball, med ball, or fitness ball) is a weighted ball roughly the diameter of the shoulders (approx. 14 inches). Medicine balls come in a variety of weights from 2lbs. to 30lbs. and can be made of hard plastic, dense rubber or synthetic leather material. Exercise Instructions Step 1 Start in a standing position with your feet shoulder width apart while holding the medicine ball at chest height. Step 2 Alternating legs, step forward into a lunge position while pressing the medicine ball over your head at the same time. Step 3 Push your body back up to the standing position while lowering the medicine ball back to your chest and repeat with the other leg.