This exercise is a wonderful exercise to build hip strength to help stabilize your hip and pelvis for walking but also to reduce shearing at your low back that can create back pain. Be particular with this exercise, it's easy to cheat. Start in a standing position, core engaged. The leg that you stand on will get a great stabilization workout if you keep your hip under you. Don't let it drop to the side. Keeping your knees beside each other bend your knee lifting your heel toward your bottom. Do not arch your back. Slow and controlled. Add Ankle Weights or Exercise Bands for more of a challenge. You should feel this in your hamstring muscles that are located at the back of your thigh.