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Heads up, everybody: We’re excited to share that we also recorded a podcast in which we cover this nuanced topic in an engaging, digestible, and conversational way. It’s episode 4 of our podcast: Yoga Meets Movement Science(!!)

Have you ever been taught to “pull your navel to your spine” in your yoga, Pilates, or fitness class? Other similar instructions you may have heard are “draw your belly inward,” “hollow your abdomen,” and “pull your navel in.” In the yoga world, we also have a similar practice specific to our tradition called uddiyana bandha.

(Note: “bandha” is a Sanskrit word that means “lock.” In the yoga tradition, the bandhas have certain philosophical roots, but in this article I’ll be focusing on the biomechanical explanation often given for them by modern postural yoga teachers in the West.)

All of these navel-to-spine cues are generally taught with the intention of stabilizing the spine by activating two specific muscles of the core region: transverse abdominis (our deepest anterior abdominal muscle) and multifidus (a muscle of the spine). These two muscles are widely believed to be important spinal stabilizers, so by “drawing in,” the idea is that we co-activate these muscles to protect our spine from potential injury as we move.

Today I’d like to examine the common practice of teaching spinal stabilization cues by asking two important questions:

Is our spine an inherently unstable structure that needs protecting in yoga, Pilates, and fitness classes?
If so, are navel-to-spine cues the best means of protecting it?

What is spinal “stability”?

Before we can address these questions, we should first establish what we mean by the term “stability.” Stability has a variety of definitions, but within the context of today’s conversation, stability means the ability of a system to return to an orientation after a perturbation. For example, trees are stable structures. They move and bend with the wind (a perturbation), but after the wind stops blowing, they return to their original orientation.

Likewise, picture a person in plank pose. Suppose someone were to bump them from the side. If the person returns to their original plank position after being bumped (perturbed), they would be considered stable in their plank pose. If, on the other hand, they fall out of plank pose when bumped, their plank pose would be considered unstable (because they could not return to their original position after being bumped).

The same logic applies to the spine. A “stable spine” is one that can return to its position and maintain its structural integrity after a perturbation or “jostling.” An “unstable spine” would be susceptible to structural compromise in the face of perturbations. By this definition, a normal spine is inherently stable. True structural or mechanical instability of the spine is relatively uncommon and typically requires some sort of trauma or surgery.

When we teach navel-to-spine cues with the intention to protect or stabilize the spine, we are presuming that the spine is unstable and vulnerable to injury as the result of the movement we’re teaching. We’re also assuming that this “drawing in” maneuver will serve to stabilize our students’ spines. These are two BIG assumptions.

Where do these beliefs about the spine originate?

About 25 years ago, there was some famous research that found that people with low back pain tended to have a slight delay in the firing of their transverse abdominis and multifidus muscles compared to people without back pain. (This delay was a matter of milliseconds.) Many people interpreted this finding to mean that these muscle timing issues caused back pain, and it was therefore extrapolated that

Transverse abdominis and multifidus are the most important muscles of spinal stabilization
To treat and prevent back pain, people should practice abdominal hollowing (navel to spine) to activate these muscles during their movements
To treat and prevent back pain, people should also practice core stability exercises to strengthen these important muscles. Here are some examples of common core stability exercises:

These early beliefs went on to spawn a huge trend in the fitness, Pilates, and yoga worlds of emphasizing the importance of “core stability” in general, and lots of navel-to-spine cueing specifically.

In fact, I recently polled my Instagram audience with the question “Do you teach or practice ‘navel to spine’ (or similar cueing) in your yoga/Pilates/movement classes?” An overwhelming 70% of respondents answered yes! Clearly today, 25 years after this research was originally conducted, these trends are still thriving.

On second thought…

Although these ideas about the core might seem to make sense on the surface, when we take a closer look, we start to see that the logic underlying them is actually flawed.

For one thing, although research suggests that core stability exercises can help with low back pain, research also suggests that core stability exercises don’t help any more than general exercises do for back pain. It turns out that movement in general can be excellent for low back pain. In most cases, this movement probably doesn’t need to look one specific way (i.e. specially-targeted core stability exercises like bird dogs and dead bugs). Even walking has been shown to be effective for reducing back pain!

Additionally, remember the research from 25 years ago showing that people with low back pain also had delayed core muscle firing? Although people interpreted this to mean that these muscle firing delays caused these people’s back pain (and therefore everyone should practice abdominal drawing-in and core stability exercises), the reality is that this research did not actually show this! The research only showed a correlation between low back pain and these muscle firing delays – it did not demonstrate causation.

In fact, it could just as easily be the case that these people’s muscle firing delays were caused by their low back pain. We truly don’t know either way based on this research! In fact, pain has actually been shown to change muscle activation patterns in other research, so it’s not far-fetched to imagine that this could explain the correlation seen in the research. Therefore, the baseline belief that muscle firing delays cause back pain and should be counteracted with navel-to-spine engagement is an assumption that should be questioned.

But that’s not all!

Later research investigated which muscles are involved in spinal stability and it found that stabilization of the spine is a global job coordinated by all of the muscles of the trunk – not simply the transverse abdominis and multifidus muscles on their own. Additionally, the requirements for spinal stabilization are dynamic and continually changing based on the movement task at hand. And this entire complex process is reflexively (automatically) coordinated by our sophisticated nervous system on a moment-to-moment basis.

With this in mind, is teaching students to pull their navel to their spine the most effective means of helping them create spinal stability? If spinal stabilization is a global job accomplished by all of the muscles of the core, how is emphasizing activation of only two individual muscles via an abdominal draw-in (transverse abdominis and multifidus) helping this process? It’s doubtful that it is – especially considering that research has demonstrated the exact opposite. Navel-to-spine engagement actually decreases spinal stability by reducing activation in the important “outer core” muscles that also help with stabilization!

But all of that aside, another pertinent question is this: how do yoga students know how much to engage their core when they’re instructed to draw in? What percent of maximum is the right amount? How do they know when they’ve achieved that percent? Does it differ depending on the movement task, or should they use the same strategy for everything? If spinal stability is an ever-changing, moving target, how does one single, steady navel-to-spine contraction meet the stability demands of all of our infinitely varying movements?

Tradition versus evidence

These questions hopefully serve to highlight that many of our popular practices of cueing for spinal stability today might be more products of convention than research-based insights. Conscious spinal stabilization is probably not something we need to worry about unless we’re in a very high-load situation like heavy weightlifting. Our spine is also a strong and robust structure that isn’t prone to injury in low-load situations like yoga to begin with.

Additionally, pain is a much more complex phenomenon than most single-cause biomechanical explanations can account for. Many people have tissue changes in their spine that might be labelled as “degeneration” or “damage” and yet have no associated pain or dysfunction. Many other people have low back pain and no associated structural issue in their spine. Low back pain can actually be influenced by any number of factors from the biological, psychological, and sociological realms. It’s therefore difficult to truly know that someone’s back pain is caused specifically by a fraction-of-a-second muscle firing delay. Plus, the biological mechanism for how such a delay could actually create pain isn’t clear.

What we do know, as I mentioned earlier, is that movement can help with low back pain in many cases! And that's one reason why I would never suggest that core stability exercises are not worth practicing or teaching. Bird dogs, dead bugs, and similar movements where we’re intending to hold our spine still while we move our arms or legs are great exercises in general! They engage the core muscles, they present a coordination challenge, and they can serve as an accessible entry point for core strengthening and control.

But we might reconsider some of the language we use when teaching these movements. Are these movements helpful because they target transverse abdominis and multifidus and help stabilize our spine? Probably not. These claims are not very evidence-based and can potentially perpetuate pain for people by suggesting that their spines are unstable and vulnerable to injury.

Additionally, navel-to-spine cueing (uddiyana bandha, drawing in, abdominal hollowing, etc.) might have its place in certain circumstances, but not for protecting and stabilizing the spine. To quote a research study on spinal stabilization techniques,

“Whatever the benefit underlying low-load transversus abdominis activation training, it is unlikely to be mechanical. There seems to be no mechanical rationale for using an abdominal hollow [a.k.a. navel to spine], or the transversus abdominis, to enhance stability.” (Grenier & McGill, 2007)

There’s so much more that could be addressed in this conversation, but in the interest of keeping this piece a reasonable length, we’ll pause here. If you’re intrigued and would be interested in a more in-depth discussion of this topic – plus a full presentation on a modern understanding of the core and spine in general – consider taking the new workshop that just launched on my website: Applied Anatomy for Yogis: The Spine & Core! You can watch it for free with the 7-day trial on my website, and it counts for continuing education hours with Yoga Alliance. I’d be excited to see you there!

Remember to listen to Episode 4 of the new Yoga Meets Movement Science Podcast (!!), where we’ve discussed this whole topic in an engaging, conversational, and informative way. Learning about new ideas through multiple channels (reading and listening!) can be so helpful for reinforcing our understanding and comprehension.

“See” you on the podcast!

References

Grenier, Sylvain G., and Stuart M. McGill. "Quantification of lumbar stability by using 2 different abdominal activation strategies." Archives of physical medicine and rehabilitation88.1 (2007): 54-62.

McGill, Stuart M., et al. "Coordination of muscle activity to assure stability of the lumbar spine." Journal of electromyography and kinesiology 13.4 (2003): 353-359.

Saragiotto, Bruno T., et al. "Motor control exercise for chronic non‐specific low‐back pain." Cochrane Database of Systematic Reviews 1 (2016).

Shnayderman, Ilana, and Michal Katz-Leurer. "An aerobic walking programme versus muscle strengthening programme for chronic low back pain: a randomized controlled trial." Clinical rehabilitation 27.3 (2013): 207-214.

Smith, Benjamin E., Chris Littlewood, and Stephen May. "An update of stabilisation exercises for low back pain: a systematic review with meta-analysis." BMC musculoskeletal disorders 15.1 (2014): 1-21.