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. Chest Strengthening the chest muscles will help you push things easily and effortlessly. The muscles in your chest help stabilize your shoulder joint, which reduces your vulnerability shoulder joint injuries. Working your chest muscles also has an aesthetic factor (body contouring). Exercise Instructions Step 1 Start in a standing position with your feet shoulder width and our arms at your side. Step 2 Hit the deck into a push-up position with your chest and thighs on the ground. Step 3 Jump back up to your feet and jump up vertically.