Begin on all fours. Your hands should be directly under your shoulders, and your knees should be directly under your hips.
Keep your right knee at a 90-degree angle as you slowly raise your leg behind you. Your heel will move toward your butt. At the end of the movement, your thigh will almost be parallel to the floor. Make sure to keep your back flat — no arching.
Squeeze your glute, then slowly return to start position.
Don't allow your knee to touch the floor before beginning the second repetition. Complete 15-20 reps, and then switch legs.