A crunch is one of the most common abdominal exercises, but it fails to accomplish the two most common goals of abdominal work: protecting your lower back from injury and toning your mid-section.
If you can perform one single crunch, you have a six pack. Whether you can see it is a matter of body fat. Decreasing body fat is a function of cardiovascular exercise and sound nutrition. Crunches may enhance the appearance of your rectus abdominus, but this comes with some risk.
To understand the risk, let’s talk about your core–which is designed to stabilize the spine. Comprised of the transversus abdominus, deep spinal extensors, diaphragm and pelvic floor, your core acts to minimize movement of your spine. This is a positive for your spine because a stable spine is a healthy spine. Crunches and pelvic tilts require flexion of the spine (think of slouching in front of the computer): the opposite of stability!
Crunching and slouching place your spine in nearly identical positions. We know slouching is not good for our spine, but crunches remain a very common exercise. The repeated flexion of your spine produced by crunches places stress on your vertebral discs and ligaments. Over time, this cumulative stress can increase your risk for lower back injuries, including disc herniation and lumbar radiculopathy, commonly referred to as sciatica.
Instructing proper engagement of the transversus abdominus is beyond the scope of this article, but a good starting point is to focus on pulling your belly button inward, toward your spine. This should be done without holding your breath and without moving your spine (no pelvic tilts!). Try to hold your contraction for 10 seconds and repeat 5 times.
It might take a few weeks of practice to become proficient with this movement, but it is worth the investment because it is the foundation of true core exercise. When you feel as if you are getting the hang of it, start engaging your core for 10 second intervals during different activities, such as walking or sitting in your car for the duration of a red light.
Exercises like planks, side planks and pallof presses correctly emphasize stability of the spine. You can even work your core by keeping your stomach firm while performing other exercises, such as pushups, rows, or squats. The difference is that your ability to keep your stomach tight should be the limiting factor for these exercises. For example, if you can perform 15 pushups with good form, you are doing a great job of strengthening your chest and triceps. However, if you want to focus on your core, you would perform only as many pushups as you can with your transversus abdominus engaged. If you feel your stomach fatigue at seven repetitions, the exercise is done because you have fatigued your core.
Bottom line: If your goal is to work your core or decrease your risk of lower back problems, you can do far better than a crunch!
