You’ve probably heard it before, but you really don’t have to do another crunch. (No, really—don’t. They’re bad for your posture, among a host of other ills.) Instead, use these exercises to firm, flatten, and contour your waistline by training your abs, obliques, and back muscles to resist bending motions and stabilise your core, which is what they’re designed to do. Get a flat stomach before summer with progressive weekly ab workouts that work
