Step 1: Sit down and place your hands under your shoulders with fingers pointing forward. Lift the hips off the floor and walk the feet out until they’re completely extended. Look up at the ceiling. This is your reverse plank position.

Step 2: Flex the feet to make it easier and squeeze the glutes to keep the hips lifted. You should not feel this in the lower back. Pull the belly button into the spine.

Step 3: Lift one leg up as far as you can without dropping your hips. This distance will vary for each individual.

Step 4: Replace the leg on the floor and switch sides. Exhale as you lift; inhale as you lower. Source: