Stand with your feet shoulder-width apart, knees slightly bent. Raise the right knee up until it creates a 90-degree angle. Bring your arms up in front of you so that your hands are in line with your shoulders.
While keeping your hips square, hinge at the hips and lower your torso until it's parallel to the floor. While you do this, extend the leg behind. The key here is to coordinate the movement of the torso and the legs.
In one controlled motion, come back to the starting position.
Continue this for 45 seconds on one side, rest, then another 45 seconds.