HOW: Get set-up on your forearms and knees in a modified plank position. While maintaining good form, lift one leg up in the air behind you by performing hip extension, hold for a second then lower back down. Perform on the other side and repeat.
FEEL: You should feel your core muscles and hip flexors working on the side that is not lifted in the air while feeling your glutes working on the other side to lift the leg into the air.
COMPENSATION: Do not arch your back or let your body/hips rotate side to side as you lift each leg. Don't let your hips sag