This exercise is my secret weapon to help tighten and shrink my waistline. It works the deep abdominal muscles (obliques, transverse abdominus) that many abs exercises don’t reach.
How to do it: Lie on your left side with your knees straight. Prop your upper body up on your left elbow and forearm. Raise your hips until your body forms a straight line from your ankles to your shoulders. Hold this position for 30 seconds. Turn around so that you’re lying on your right side and repeat.