Sit-ups are one of the most popular core training exercises for people of all ages. Everyone does sit-ups, but most people have no idea why. As it turns out, they actually cause more harm than good. A basic sit-up creates about 730 pounds of compression on the spine. Too many sit-ups, and you could be facing serious spinal injuries instead of showing off your toned tummy. The point of your abdominals is to stabilize the torso, meaning they need endurance more than strength. So the next time you hit the gym avoid sit-ups. There are better, safer ways to work your way to a flat stomach!