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. Hamstrings The hamstrings play a crucial role in many daily activities, such as, running, jumping, walking and cycling. Strengthening your hamstring muscles help to protect your knees from injury by absorbing the stress placed on the knee. Weak hamstrings can lead to knee injury. Exercise Instructions Step 1 Start in a split lunge position with your feet about shoulder width apart and your knees and hips flexed at a 90 degree angle. Step 2 Jump up and quickly switch your stance so the opposite foot is in the front landing with your feet shoulder width apart. Step 3 Make sure you keep your back upright and your chest proud throughout the entire exercise.