Step 1: Grab something with some weight to it – a book, a ream of printer paper, a hand weight if you have one.
Step 2: Stand with your feet slightly wider than hip-width apart.
Step 3: Hold the book out in front of you, about four inches away from your chest with your elbows bent.
Step 4: Contract your abs. While keeping your hips stationary, rotate your torso and the book from side to side.
Step 5: Do 30–50 reps.