In fact, Alwyn Cosgrove, C.S.C.S., blames the dead for our obsession with crunches. He says, "If it weren’t for dead guys, we’d probably never have started doing crunches. That’s because for years, much of our knowledge of the way muscles work was based on the study of human cadavers. By looking at the anatomy of corpses, modern scientists figured that the function of our abdominal muscles must be to flex the spine. Which is exactly what you do when you perform a crunch, a situp, or any other move that requires you to round your lower back. As a result, these exercises were popularized as the best way to work your abs.
"But the reality is that your abs have a more critical function than flexing your spine: Their main job is to stabilize the spine. In fact, your midsection muscles are the reason your torso stays upright instead of falling forward due to gravity. So your abs and lower back actually prevent your spine from flexing.
"The upshot is that if you want better results from your core workout, you need to train your abs for stability."
So what exercises should you do to work your abs?
First of all, you want to perform exercises that focus on core strength. The primary function of your core (the muscles that surround and corset your spine) is the stabilization of the spine and pelvis. There is some debate about the exact number of muscles that should be included in the term “core.” However, contrary to popular misconception, core is not a synonym for abs.
For a healthy, sleek, and functional midsection, you need to work all the muscles embedded in the front, back and sides of the core.
Forget traditional crunches or sit-ups, they’re inferior for core strength and terrible for your back. Variations of planks (including side planks), “bird dogs” and anti-rotation exercises are superior to crunches and sit-ups for a fit and healthy core.