Start in a plank position. Move your right leg slightly in toward your center line, and lift your left leg off the ground so your heel is even with your pelvis.
Keeping your torso steady, reach your right arm forward. Really brace through the abs by pulling your navel to your spine. Hold this position for 30 to 60 seconds.
Repeat on the other side for another 30 to 60 seconds, then rest for 10 seconds.