Ab Training

November 19, 2011

Evidence-Based Core Training

First off, I want to apologize for my lack of recent posts to the blog. I’ve been swamped with projects as well as a seemingly endless sea of papers associated with my Ph.D. studies. Hopefully my workload will ease a bit in the coming weeks and I’ll have more time to provide ongoing content.

In the meantime, I wanted to take this opportunity to comment on the reaction by a select few fitness professionals to the review paper that Bret Contreras and I wrote titled, To Crunch or Not to Crunch. A small but vocal portion of the strength and conditioning community seems to feel that it’s heresy to challenge their dogged position that crunches are inherently evil. One strength coach has gone so far as to claim that we were “deliberately trying to be controversial” by stating that spinal flexion exercise is not necessarily a one way ticket to back surgery. Amazing! I’m of the belief that it’s controversial to claim the crunch — an exercise that has seemingly been around since the dawn of man — has no place in a person’s training routine. Go figure…

Here are the facts: Bret and I are not only practitioners, but scientists as well. When we wrote the article, our sole intention was to seek the truth. We reviewed hundreds of peer-reviewed articles on the subject — pretty much every study that was in any way related to spinal flexion — and took an unbiased view in our reporting of what we found. Based on the body of literature, there simply is not sufficient evidence to support the contention that healthy individuals should abstain from performing crunches. Moreover, there is even some research to suggest that it may have a positive effect on spinal health. Should evidence come out in the future that refutes these findings, we’ll be the first to acknowledge it and rethink our position. But as evidence-based practitioners, the recommendations we made in our paper are solidly in line with current research, personal experience, and the needs of the individual. This is the essence of evidence-based practice.

Are crunches for everyone? Certainly not. We clearly state in the article that they should be avoided by those with existing spinal issues such as disc herniation, disc prolapse, and/or flexion intolerance. But understand that the same is true for any exercise. Squats, presses and rows are all terrific exercises, but they may be contraindicated for a given individual depending on his/her goals, abilities, and injury status. As Stuart McGill has been aptly quoted as saying subsequent to publication of our article, “Crunches are neither bad nor good. The most important thing is the assessment to determine what’s right thing for the person in front of you. The next most important thing is to respect the load/posture/repetition variables in your algebra, i.e. don’t overwork the tissue beyond the ability to adapt or beyond its tolerance to failure.” I couldn’t agree more.

Unfortunately, there are those who choose to take a cult-like stance with respect to fitness. Rather than embracing new information, they instead cling to their rigidly-held beliefs and flame against anyone who poses a threat to their stance. This kind of attitude is not only unscientific, it’s unprofessional and can only set back exercise science and have a negative effect on the fitness industry as a whole. Ultimately everyone loses, including the general public who are caught in the crossfire.

Here’s an interesting anecdote. Back in the early 1960’s, a professor from the University of Texas named Karl Klein railed against the performance of deep squats. Klein conducted studies showing that weight lifters who frequently performed deep squats displayed an increased incidence of laxity in the collateral and anterior cruciate ligaments compared to a control group that did not, leading him to conclude that squatting below parallel had a detrimental effect on ligamentous stability. “Anything below a half knee bend,” he was quoted as saying in a 1962 Sports Illustrated article, “is useless and ruinous.” (Side note: The SI article was ironically titled “The Knee is Not for Bending.” Sound familiar? The similarities are eerie).

Now Klein was a distinguished researcher at the time and, as you may imagine, his claims had far reaching implications: The US Army subsequently removed squat jumps from their training protocols; the New York State school system banned deep knee bends from gym class; and the American Medical Association came out with a position statement cautioning against the performance of deep knee exercises because of their potential for severe injury to the internal and supporting structures of the knee joint. The upshot: For years, deep squats were widely considered passe. In fact, due to one man’s crusade, the negative view of deep squats is still being felt 50 years later as some continue to admonish the exercise as inherently dangerous.

Fast forward to today. Research has ultimately refuted Klein’s findings. No correlation has been found between deep squatting and ligamentous stability, including results from studies that attempted to replicate Klein’s methods. In fact, the prevailing body of evidence shows that ACL and PCL forces actually diminish at higher knee flexion angles. I covered this subject extensively in my NSCA Hot Topic article, The Biomechanics of Squat Depth. If you haven’t already given it a read, you may well find it enlightening, especially in the context of the current controversy over spinal flexion exercise. Could there be any parallels between the two topics? As they say, time will tell.

Bottom line is that it’s fine to have an opinion on a subject provided you’re open to other viewpoints. With respect to spinal flexion, I encourage you to read the research and draw your own conclusions rather than being swayed by some opinionated “fitness guru.” With a firm understanding of the available evidence, we can then debate the topic logically, rationally, and civilly to facilitate a better understanding of the issues. We shouldn’t care who is right or wrong, just that we ultimately get it right. Only through an open exchange of ideas can science move forward. This way, everyone wins.

Stay Fit!



  1. I actually got a huge smile when this popped up in my feed. Welcome back Brad. I enjoyed the article in the NSCA journal and appreciate that you’ve put this topic to rest (at least until another pig unfortunately loses his skeleton).

    Despite being a huge advocate of McGill’s work and avoiding excessive flexion I never took crunches out of my programs completely. It just didn’t make sense. To me the reality was that my clients were going to flex at their lumbar spine over the course of their days, there was no avoiding it. I decided that I would serve them best by at least helping them strengthen the muscles responsible for that pattern and, in McGill’s words, groove that pattern.

    I mean, I didn’t want somebody to bench press their weight and not be able to get up from the bench. It just seemed absurd.

    Comment by Jonathan Goodman — November 20, 2011 @ 9:46 am

  2. There is not such thing as a bad exercise. Just bad selection of exercise for an individual

    Comment by Patrick — November 20, 2011 @ 10:38 am

  3. Many thanks, Jon. Appreciate your feedback and your balanced approach to fitness 🙂


    Comment by Brad — November 20, 2011 @ 12:19 pm

  4. Agree with you wholeheartedly, Patrick.

    Comment by Brad — November 20, 2011 @ 12:20 pm

  5. Thanks for the great post, Brad!

    It’s entirely true that if we’re going to advance our profession both in the eyes of the general public – the folks we’re supposed to be helping – and other health care professionals, that we need to grow beyond anecdotes and mythology. The very basics of good coaching require that we verify through repeatable, scientifically sound research the methods we use with our clients! We also need to be humble enough to realize that our field is constantly growing and changing and therefore we need to be open to change.

    Twenty five years ago I was writing articles on performing longer, low intensity cardio work for the best fat loss results – now I still recommend that as a starting point for someone who is deconditioned or orthopedically challenged – but science has since shown us that there are more effective ways to enhance extended fat loss.

    Of course the other giant elephant in the room in regards to fitness paradigms that have finally started to correct themselves is the way that so many fitness pros abandoned static stretching because the “gurus” told us that it was a waste of time. Now we know that dynamic and static stretching both have their place in our programming and it’s simply a matter of knowing where they best fit the needs of our clients.

    I’d highly recommend a site – don’t be a knee jerk skeptic because of who they are – for some great research links in regards to many controversial topics in fitness:

    Some great stuff here on balance training, functional training, knee postioning, etc.

    Comment by Pat Marsh — November 20, 2011 @ 1:11 pm

  6. ACSM promotes partial crunches to 30 degrees to avoid excessive spinal flexion. Are you saying that you should still do full-sit-ups?

    Comment by Tim G. — November 20, 2011 @ 5:13 pm

  7. Thanks for the feedback Pat. Cybex puts out some good stuff. I generally like their work.


    Comment by Brad — November 20, 2011 @ 5:33 pm

  8. Hey Tim:

    The traditional crunch is only performed to 30 degrees of spinal flexion–it is distinct and different than the sit up. The thoracic spine only has about 30 degrees of mobility.


    Comment by Brad — November 20, 2011 @ 5:35 pm

  9. I find that there are four distinct factions in the fitness world.

    1. Those who read research, but have no practical experience to temper their judgements of applicability.

    2. Those who read research and seek to apply the results in practice.

    3. Those who read the writings of those who report only findings in research that support their inflammatory beliefs (i.e., Mercola, Taubes, etc).

    4. Those who think reseach is useless and can only quote Wendler’s popular “You want science and studies? Fuck you, I’ve got scars and blood and vomit.”

    I think we need more of faction number 2…but they are sadly few and far between.

    Comment by Mark Young — November 22, 2011 @ 10:39 am

  10. Couldn’t agree more, Mark. Thanks for the feedback 🙂


    Comment by Brad — November 23, 2011 @ 10:17 am

  11. […] Evidence-Based Core Training -Brad Schoenfeld. […]

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