[sidebar]Instead, you should work up to doing crunches. These are similar to sit ups but you’re bringing only your head, shoulders and upper back off the floor. Crunches are much more effective because they specifically target your abdominal muscles—not your hip muscles, which are used during a full sit up. If you’re still having trouble doing crunches, start with pelvic tilts. Lie on your back with your knees bent and feet flat on the floor. Pulling your abs in, press the small of your back into the floor so that your pelvis tilts upward. (This is a very small movement; your buttocks should not come more than an inch off the floor.) Hold for about three seconds and then slowly release. Do 8 to 12 of these at least three times a week. This will help strengthen your abs and make crunches more effective. By maintaining a pelvic tilt when you’re doing crunches your abdominal muscles work harder. Another important thing to remember is to use your abdominal muscles throughout the day. Tighten your abs (but don’t hold your breath) when you’re sitting and standing so you maintain good posture. Slouching just stretches and weakens your abs. More from Prevention:8 Flat Belly Shortcuts
