Lie on your back with your arms extended straight over your head so your body forms a straight line. Bend your knees and keep your feet flat on the floor then – keeping your arms locked – contract ...

Whether you're a frequent or infrequent gym-goer, there's a good chance you've done crunches. Crunches are a classic core-strengthening exercise. But while they may seem ubiquitous — heck, they're ...