Don’t believe it just because you read it on the internet. Or because an ‘expert’ wrote it. One exercise physiologist and personal trainer who wrote to me certainly didn’t. Fair enough. But ‘prove it’ when referring to why NOT to do something can be a little tricky…

So, somewhere I had written this:

“Exercise ‘knowledge’ does women a diservice, by having us believe that we must… perform crunches and planks to exercise our abs”

There was a context, about core and pelvic floor function being a whole body issue etc, but this was the sentence quoted:

“What kind of scientific evidence do you have to say:

[insert my quote above] ?

I am a research scientist and have found nothing to support your comment. Please be more specific and support with a research. Thank-you.”


Where indeed?

And because I find that often if one person is asking, others are wondering… I thought I’d share some of my answer.

To clarify, I’m not saying there is no benefit to a plank, or that they are ‘bad exercises’. I’m rather partial to the occasional plank myself. I’m saying they won’t always be the best exercise, depending on who’s doing them and how. I’m suggesting that this isolated, isometric exercise, performed when the core muscular system is not functioning optimally, may not be either effective or beneficial.

A plank can be a very effective ab exercise. But it would not be recommended by most Women’s Health Physiotherapists for the postpartum woman. Not until her core is restored and functional again.

You can read some medical comments on appropriate exercise here. And here’s some guidelines on what it is ok to feel postpartum… and what isn’t, and when you should stop doing that thing you’re doing, which may be a plank…

Postpartum core strength is about a whole lot more than holding a plank.

A great article that describes the complexity of factors likely to be relevant to the postpartum core can be found on Diane Lee’s site here. For science-focussed resources on pelvic and core health research, as well as Diane Lee (always heavily research-referenced), other professionals well worth reading are Julie Wiebe PT and Biomechanist Katy Bowman. The Integrative Pelvic Institute and Pelvic Guru are also great evidence-based resources.

I also love this very insightful and resource-packed article on the real meaning of scientific proof, also by Katy Bowman.

What I am suggesting, is that the commonly held belief that planks are the best ab exercise, is inadequate for dealing with the multi-fascial, multi-functional, multi planar complexities of a non-functioning core.

Thats my point. Not that these exercises are bad. Rather that they may inappropriate in some cases or at some stages of postpartum recovery.

The rationale behind this assertion of mine is not a particular research paper that told me so, but rather it is based on study and collaboration with medical and fitness professionals’ research, knowledge of biomechanics (whole body alignment), pelvic floor function, breathing mechanics and fascial systems. It’s also based on the great many examples of clients and patients who have restored their core with exercises such we would recommend, as well as many examples of women who did traditional ab exercises such as crunches or planks postpartum, and experienced detrimental effects.

As far as I’m aware, ‘Proof’, where proof refers to a long-term, double-blind study, that a specific isolated exercise may be effective for some (for example an athlete with a functioning and strong core) but inappropriate for others (for example a postpartum woman with diastasis recti and pelvic floor disorder) doesn’t exist. If it does, then please let me know in the comments here. But I believe there is (fortunately, actually) little approval or demand for studies setting up a defined group of people to do something potentially harmful to observe just how bad the outcomes might be. And incidentally, *not doing a plank* is not a particularly risky strategy, so there’s only so much evidence beyond being mindful of how it looks and feels, that we surely require to make that choice?

In the same way that there are recognised recommended exercise adaptations and contraindications for the pregnant woman, so is also the case in the postpartum period. It doesn’t mean no woman should ever sky-dive or play contact sports, merely that it’s not considered to be a great idea when pregnant or recently post-childbirth… We don’t need 2 comparative groups of women to participate in that study to be confident that it’s sensible advice.

To further clarify on the basic facts of the exercises themselves: Isolated ‘ab work’ such as a plank or crunch (indeed any high load exerting movement, like a push up, pull up or lift) increases intra abdominal pressure. As in, it creates increased load that must be contained – this is simply the physics-based biomechanics of the movement.

The core’s function is to withstand load (pressure) and to facilitate transfer (movement). If it can’t withstand relatively low load, for example when standing, (evident from a pooched out, or domed stomach typical of a diastasis), then it definitely won’t be able to withstand very high load (such as holding full body weight in a prone position like a plank).

Further, performing higher frequency or higher intensity high load, high pressure movements, will not strengthen an already non-functioning muscle group. It needs to function effectively, before it can strengthen. See more on ‘When Are You Ready To Crossfit or Plank?’ here.

I’m not at all convinced that planks should be recommended as the ‘go-to’ exercises for improving ab function and strength for postpartum women. I think we need a core that works first. We empower ourselves with as much information and evidence as we can. We observe and we feel how our bodies respond to the demands placed on them. And then we think critically and make a choice to keep doing what we’re doing or change what we’re doing.

It’s important to say too, that this post isn’t actually about planks. It applies to any exercise – hence my reference earlier to all high-load or high-intensity exercises. Prone, supine, standing… isometric or dynamic, any plane, any position:  If your alignment and form is ‘out’, if your core isn’t ready, the exercise won’t have the desired effect and could exacerbate the problem.

But on this occasion, I was asked about planks 🙂