MUSCLES ENGAGED 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). 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. Exercise Instructions Step 1 Start in a standing position with your feet shoulder width apart. Step 2 Jump down into a push-up position and lower yourself to the ground with full control. Step 3 Press yourself back to the top of the push-up position, jump up and fully extend into the air.