Instruct students to stand with their feet shoulder width apart and their hands on their hips. Have them be sure to keep their stomach muscles tight and their back straight in line with your hips. Tell them to lunge forward with one foot, being sure to keep the knee straight in line with the ankle. Remind them not to let the knee go over the toe when they lunge. Have them slowly squat down, gently touching their back knee to the ground, and slowly raise their body back to standing. Step forward and repeat with the opposite leg in front. They can perform the lunges in place, or they can start at one end of the hallway or gymnasium and perform the exercise across the space available. To make the exercise more challenging, students can put their hands above their heads, or even hold a medicine ball, or a heavier object to add more resistance.