Start in a side plank position on your right elbow, with your feet staggered so your left foot is just in front of your right. You can also stack your feet for more of a challenge.
Reach your left arm up toward the ceiling, and maintain a straight line from head to heels. Try not to let your hips drop toward the floor, and avoid hinging at your hips.
Hold for 15 seconds to one minute on each side (depending on your level).