A couple of years ago, I told my husband to stop doing sit-ups.He stared at me in disbelief, midcrunch. “They’ll hurt your back, and there are much more efficient ways to train your core,” I pressed. He finished his rep.Last week, he showed me an article in The New York Times that shared my same “anti sit-up”sentiment. “So, what did you think of the article?” I asked hopefully.  “Hmm, I don’t believe her either.”Why do we insist on doing sit-ups?Is it because of those Presidential Fitness tests from grade school? Boot camp workouts?  Commercials for eight minute abs? Is it because beautiful bodies in the movies perform various iterations of them: Rocky grunting through straight-body reverse lifts. Richard Gere in “An Officer and a Gentleman” doing thousands upon thousands of basic sit-ups. “Kung Fu Panda” executing the hanging from the knees variety?MORE: Beauty Benefits of Exercise Usually, when an expert give us license to stop doing something that takes time and lots of effort, we sigh with relief and never look back.But not sit-ups.We find it impossible to believe we’ll be OK without them.  It’s like we’re afraid our abdomens will balloon out under the pressure of our organs.When it comes to abdominal training, many myths abound, asserts Stuart McGill, a professor of spine biomechanics at the University of Waterloo in Canada and a noted expert and clinician in spine function, in his book “Low Back Disorders.” Some common sit up beliefs with little or no backup evidence:-        Performing sit-ups will improve back health.-        Yoga and Pilates classes are good for the back.-        Bending the knees when doing sit-ups takes the strain off the back.-        Strengthening the core muscles protects the back.To understand why sit-ups and other forms of high intensity abdominal training are unnecessary and often damaging, you need to appreciate the functional role of your abdominal muscles. Your abdominals and other core muscles keep your upper body (your torso) stabilized on top of your lower body (your pelvis) during movements such as walking, running, pushing, moving side-to-side, etc.If they did not engage during movement, the torso would lag behind the lower body, and you would look like one of those giant inflatable air dancers waving, swinging and flapping in the wind. Given this basic function, the abdominals are rarely a primary mover but mainly a stabilizer. They’re a set of muscles designed to combat the effects of gravity and inertia, a job with very long hours. These muscles require more endurance than they do strength.So among all of the abdominal exercises that exist, what makes sit-ups so sinister?  Their popularity.QUIZ: Take the Body Health QuizMany common abdominal exercises, including leg raises, should be avoided as well, but sit-ups are the most common and most propagated. Here are six reasons to leave sit-ups behind:1. Your abdominals prime function is to stabilize. They should be trained as stabilizers and not as primary movers. In other words, you’re not going to lift your luggage with your abdominal muscles.  Rather, your abdominals will help stabilize your spine and protect your back as your shoulders and arms do the primary lifting.2. Your abdominals function in conjunction with other muscles in the torso as well as the shoulder girdle and pelvis.  Therefore, integrated, functional movements provide challenge enough for these muscles. Sit-ups train the abdominals in a position completely removed from the demands of their natural function.3. Sit-ups create high compression forces in the spine that, with repetition, increase your risk of back injury. McGill and Axler found that a basic sit-up inflicts about 730 pounds of compression on the spine, the action limit set by the National Institute for Occupational Safety and Health. This means that workers who experience repeated loads any higher than that of a sit-up have increased back injury rates. Your discs can withstand flexion (curving forward) and compression only so many times before they bulge or herniate. The damage is cumulative. Why not use these times for actual living situations rather than exercising? (Hint: if your back does not tolerate sitting for lengthy periods, likely the effects of repeated compression and flexion have already begun to show.)4. Your spine is supported and stabilized by many muscles along the front, sides and back of the torso. McGill uses a fishing rod as the model for the spine, with the various muscles of the trunk acting as guy-wires coming off the rod at many levels and in many directions, all pulling at just the right tension to keep the rod straight. If you strengthen any one muscle or group of muscles to a larger degree than another muscle or group of muscles, it can create an imbalance in the pull or the activation of muscles in the torso, causing instability and buckling in the spine.5. Sit-ups are not the key to a flat stomach. High-resistance abdominal training can create hypertrophy in the abdominal muscles and will not lead to a flat abdomen any more effectively than functional activities will.6. Sit-ups generate an outward and downward pressure in the abdomen. For women who have had children, this pressure can exacerbate the separation of the rectus abdominis muscle along the front of the abdomen, as well as aggravate pelvic floor laxity and weakness, perpetuating poor pelvic organ function and incontinence.MORE: Beauty Tips for ExercisersNow you’re probably thinking, “OK.  You’ve taken away everything precious to me. What the heck am I supposed to replace it with?”Following are the two most basic and beginner abdominal exercises recommended by McGill. He provides other basic and more advanced core exercises in his book “Ultimate Back Fitness and Performance.”-        Curl-Up: Lie on your back with one leg bent 90 degrees and the other extended flat on the floor. Place your hands under the arch of your lower back. Lift your head and shoulders just off the floor by using your abdominals to curve your thoracic spine (mid back), leaving the neck (cervical spine) and low back motionless. Hold up to eight seconds, while continuing normal breathing, and repeat several times.-        Side Bridge: Lie on your side, with your elbow and hip supporting you and your knees bent 90 degrees. Straighten your torso until the hip lifts off the floor and you are supported by your forearm and side of your knee. Hold the position as tolerated (with proper form and no pain) and repeat several times.You don’t have to damage your back or aggravate other conditions in the process of obtaining a strong, resilient and beautiful core.In coming articles, we’ll focus on functional exercises that give you the endurance your core needs and help you achieve the look that you desire.