We all want a toned, flat stomach. No surprise there. But since many women are still relying on crunches to get it, we want to make one thing clear: Crunching is not the most effective abs workout. “Crunches work only the muscles on the front and sides of your abdomen, but it’s important to target all the muscles of the core to get more defined abs—including lower back, hips, and upper thighs,” says Lou Schuler, co-author of The New Rules of Lifting for Abs. “Core exercises like the plank help train muscles to stabilise the spine and pelvis so you can avoid back pain and improve posture”, Schuler says. “They…