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 squatting position with your arms straight, holding the medicine ball by your knee. make sure too keep your buttocks out and your back straight throughout the exercise. Step 2 Stand up and twist across your body and press the medicine ball over your head. Be sure to keep your core engaged during the trunk twist and fully extend your arms when pressing upwards. Step 3 Lower the medicine ball twist back down to the position you started with and repeat.