Start in a quadruped position. Hands under the shoulders, knees under the hips. Maintain a neutral spine throughout, and keep the hips and shoulders level.
Keep the arms straight, grip with the fingers, and extend one leg behind you. Point your toes, squeeze the glutes, and reach your foot back rather than up.
Pause at the top, left hip full extended. Actively reaching your leg behind.
Return to the start, switch sides and repeat for repetitions.