Abdominal crunches are a great core-strengthening exercise that requires minimal equipment and space. It is just too bad that a lot of people are doing them incorrectly.
The muscle targeted by the abdominal crunch is primarily the rectus abdominis (or six-pack muscle). This is accomplished by engaging the abdominal muscles through lifting the upper body off the ground and this is often one of the first exercises that people learn. Unfortunately, when an exercise is taught to a young child, that child often misunderstands the mechanics of the exercise, and because of his or her youth and relative flexibility, doesn’t realize the damage that he or she might be doing to his or her body. As that child gets older, he or she will often continue doing the exercise incorrectly until the years of accumulated damage finally catch up to the now adult man or woman, often derailing his or her efforts.
The biggest mistake that most people make is in their execution of the movement. When correctly doing a crunch, the bottom of the ribs and the top of the pelvis should remain a relatively equal distance apart and the lower part of the spine should remain off the ground. Compare this to what is often seen at the gym. Often the abdomen will be completely flexed and the spine will be curved into a ‘C’ shape. By doing the exercise this way, a great amount of pressure is placed on the lumbar spine and over time can contribute to a spinal herniation. Contributing to the pressure placed on the low back is that by over-flexing the abdomen, the body’s natural posture will change and, as a result, the front of the pelvis is pulled upward and this gradually increases the day-to-day pressure on the low back, making injury more likely.
A safer, more core-focused crunch requires a different conception of how the exercise is performed. The first and most important thing is that the idea of the exercise is not to flex the abdomen, but to engage the muscles instead. This is accomplished by picturing the body as two separate pieces connected by hinge located at the hips. So when performing the exercise, the only part of the body that should bend in a significant way is the hips. The back and the abdomen should hold their natural shapes throughout the exercise. Now with this covered, let’s go step-by-step through a proper crunch.
WARNING: If you have a pre-existing back injury, consult a health professional before proceeding.
1) Lay on your back with either the legs straight out or with the knees bent to 90°. The upper back and the sacrum (the large triangular bone at the base of the spine) should be in contact with the floor and the lower portion of the spine should be off the ground. If you place your hands flat on the floor and level with the belly button, you should be able to slide both hands under your back and use the fingertips of one hand to the touch the fingertips of the opposite hand. Your spine should maintain this shape throughout the exercise.
2) Now place your hands on your abdomen. This will allow you to feel the muscles engaging as you perform the movement.
3) Slowly lift your head and shoulders off the floor using your abdominal muscles. Your upper back and sacrum should remain in contact with the floor as you perform this action. If you picture a string coming out of your belly button, think of someone pulling directly up on this string. You should feel the belly muscles under your hands tense up. Hold the tension for a second and then slowly lower your shoulders and head back to the ground.
4) As you perform this exercise, remember to breath. If you catch yourself holding your breath, take a break as this is often the first sign of fatigue. The proper pattern for beginners is to exhale as the muscles are engaged and to inhale during the relaxation phase. Some Pilates instructors advise using the opposite of this patten (exhaling during the crunch and inhaling during the relaxation phase) but the most important thing is to breathe.
5) Repeat this exercise as many times as you can before a) you can’t maintain proper form, b) start shaking, or c) can’t keep your breathing regular. You will see more benefits from this exercise by doing it right a few times as opposed to doing a lot of repetitions with poor form or execution. In fact, by pushing too hard, you risk engaging in the same bad habits described above. This is a lifetime exercise, so there is no need to rush, but within a relatively short period of time, you should see improvements in posture and a reduction in back pain. A smaller waistline may also result.