Come down onto all fours on your mat, then lower your upper body down onto your forearms.
Stack your shoulders over your elbows and hips over your knees. Try to keep your shoulders and hips level.
Engage the abdominal muscles to support your low back and stabilize the hips.
Move:
Float the left leg off the mat. Contract and squeeze your left glute muscles to lift the leg higher than your hip, or to the height where you feel the center glute muscles turn on.
Bend your left knee about two inches, releasing the muscle contraction, and then engage the left glute muscles to straighten the leg again, this time pressing firmly into the left heel. (Imagine pressing so firmly into your heel that it's as if you can feel the glute muscle lifting off the back of the leg.) Repeat this slow, controlled bend and stretch 20 times.
Pick up the tempo and turn the movement into a slight bend and stretch behind the left knee, still activating and releasing the glutes. Repeat 20 times.