Trending The expert continued: "Bring yourself into a box position, so your wrists sit under your shoulders and knees under your hips. Take a Pilates ball in between the thighs and squeeze into the ball. “Lift your knees around two to three inches off the floor and start to make small squeezes into the ball continuously. Reset when you need to!” Side Plank with rotation (both sides) Targeting the side of the abs can help whittle down the midriff. "Lie on your side, feet together and one forearm directly below your shoulder. ‘Knit’ the rib cage in and raise your hips until your body is in a straight line from head to toe," she said.