Side plank with leg raises

Place your right elbow on the ground. Extend both legs out so that your body is in one straight line, balancing on the outside edge of your right foot. Flex both feet, and reach your left hand to the ceiling.
Keeping your spine lengthened and your abs engaged, lift your left leg up just higher than your top hip. Then slowly lower it back to your bottom leg.
Keep your waist up and lifted, and don't sink into your bottom shoulder.
Do three sets of 15 to 20 repetitions on each side