Why Crunches Don’t Work…
Written on October 20, 2008 at 7:30 am, by Eric Cressey
Q: I noticed that you include reverse crunches in Maximum Strength, but not standard crunches. Why is it acceptable to have lumbar flexion during a reverse crunch, but not during a standard crunch?
A: This is a great question – and there are a few components to my response.
First, we use reverse crunches in moderation and only in our athletes who are healthy and those who have extension-based back issues (i.e., more pain in standing than sitting, tight hip flexors, anterior pelvic tilt, dormant glutes). We wouldn’t use it in folks who have or have had flexion-based back issues (generally, this equates to disc problems and more pain in sitting).
Second, keep in mind that this is unloaded lumbar flexion; we wouldn’t add compression to the mix.
Third, and most specific to your question, reverse crunches target the posterior fibers of the external oblique more. Given the points of insertion of these fibers, you can address anterior pelvic tilt without affecting the position of the rib cage.
Regular crunches shorten the rectus abdominus. While this can help with addressing anterior pelvic tilt, you also have to realize that shortening the rectus abdominus will depress the rib cage and pull people into a more kyphotic position. This is not a good thing for shoulder, upper back, or neck health.
So, in a nutshell, if we are going to have any sort of lumbar flexion in our training, it has to be a) unloaded, b) in the right population, c) implemented in lower volumes, and d) offering us something that addresses another more pressing issue (e.g., anterior pelvic tilt).
Combat Core is an exhaustive resource on high-performance core training that I’d encourage you to check out as well.