With your palms flat, raise onto your toes in a high plank position. Keep your hands directly below your shoulders, feet at hips-distance apart, and core engaged. (You can also do this move in an elbow plank position, like Graham.)
Bring your right knee to your right elbow, keeping your body in a straight line.
Return your right foot back to the mat and repeat on the left side.
Do as many slow, controlled reps as you can for 45 seconds.