I’m sorry, I got that song stuck in your head, didn’t I? I just couldn’t help myself…
Today I wanted to have a little chat with you folks about intra-abdominal pressure (IAP)-what is it, how can we use it to maximize our patients’ benefit from therapy, and is there such a thing as too much? Now I do also want to throw out there that the research on this topic is not 100% clear, and as with anything else in the study of human beings and movement, it may be subject to change as new information comes out/studies are done. So this blog post is based on our current understanding of the topic at hand and I reserve the right to retract it if the evidence changes in 5 years!
What is intra-abdominal pressure?
Now, do realize, this is a fairly complicated concept and can and has been the subject of entire book chapters, articles, blog posts, and CE courses (I teach half and full day CE courses on this topic), so a fully comprehensive explanation is not likely in a simple blog post. However, to put it simply, intra-abdominal pressure is a key component of our dynamic stability system. “Old” spine stability teaching was that our spinal support comes directly from the action of muscles that connect to the spine and the way we increase stability is by tightening or bracing the muscles to prevent the spine from moving. We now know this isn’t accurate, and it is actually detrimental to teach people to (not) move this way. The more current concept of intra-abdominal pressure essentially says that when all the muscles making up the “core canister” (diaphragm, pelvic floor, abdominals, multifidus, obliques, etc.) are contracting together and in a balanced way, that generates a pressure within the abdominal cavity, and the pressure provides support to the spine. This is one of my favorite resources for understanding the concept of this canister and intra-abdominal pressure in general: http://www.juliewiebept.com/individual/the-diaphragm-and-our-internal-pressure-system/.
One of the key things to understanding this concept is that in an ideal scenario, IAP control should not be dependent on a bracing strategy for movement. In fact, while a bracing strategy can provide some short term symptom relief, it may set patients up for non ideal movement strategies that can have consequences down the line. When we teach a bracing strategy, we are essentially teaching our patients to increase their intra-abdominal pressure-which does provide spine support; but at what cost?
Too Much IAP?
We are probably all too familiar with the Valsalva maneuver as a movement strategy-we show people how to do a movement, or ask them to activate a muscle and then realize that their facial color is slowly darkening into red or purple as they hold their breath. We tell them to breathe, but do we really fully realize what is happening here?
A breath holding strategy is one (very effective, if not terribly functional) way to increase intra-abdominal pressure. However, in an ideal scenario, we don’t necessarily want our patients to be limited to an increased pressure system for support in movement. When there is an over reliance on increased IAP, problems such as prolapse, hernias, and incontinence can develop, and in the long term, there can be consequences in the joints as well (stiffening, over activity of muscles attached to specific joints, etc.). There are some situations where an increase in IAP is a beneficial and necessary movement strategy (think Olympic style weight lifting); however, many patients rely on this strategy for “typical” daily movements, and then increase even beyond that point for harder/more athletic movements, and that is where we can see a problem. Leakage of urine while coughing, sneezing, laughing, running, or lifting is a major red flag that can suggest that there is an over reliance on increased IAP as a movement strategy with the weakest point (pelvic floor) “giving” under that pressure. By the way, this is not a problem exclusive to women. Male patients who experience the “shart” (or sometimes urine leakage, but bowel is more common for men) during activity are experiencing the same problem, just slightly different symptom due to anatomic differences. Of course, there are multiple factors that can be a part of these symptoms and I am not trying to suggest that movement strategy is the one and only thing that ever needs to be addressed-but, if your patient with low back, hip, or pelvic girdle pain also experiences incontinence of any type, it may be worth further exploration!
Maximizing Therapy Gains
So how do we use this information to maximize our patients’ therapeutic benefit? Again, I could talk about this for days-but to put it simply, we need to move beyond just teaching muscles to activate and also teach them to coordinate. As with anything therapy related, we should be providing our patients with skilled intervention, meaning that our plan for teaching them core control should be just as patient specific as any other intervention. Some patients are going to need to start with a very basic proprioceptive awareness of where muscles are and what it feels like to activate them. Some are going to need to learn to hold a muscle contraction during pressure. But hopefully they all get to the point where we are teaching them a MOBILE movement strategy-not brace or tuck/hold, but core (and therefore IAP) control while moving.
The nice thing is, our body does know how to do this, so we don’t have to be able to figure out how to teach patients to turn on muscles (that, by the way should be firing within microseconds of one another) in a specific sequence. We do need to cue the brain to where it remembers those movement strategies and begins to use them again. How do we do that? My generic suggestions (which will need to be tweaked for each patient):
- Identify and remove barriers to movement-including joint or soft tissue restrictions that are making it difficult or painful to move AND hitting “CTRL+ALT+DELETE” on the compensatory motor patterns as needed.
- If need be, teach how to activate/feel individual muscles and then control how hard they are being activated-remember, the amount of muscle activation should be equivalent to the load you are asking it to work under, we don’t want people doing maximal contractions for all movement! Realize that much of the “benefit” of this stage is in regaining proprioceptive awareness of the muscle and improving communication between that area and the brain and treat it appropriately.
- Teach people to breathe! Diaphragmatic breathing can be such a key component to core control and mobile support/IAP control (there are tons of resources out there on this, or I am happy to write a follow up blog post if there is interest). If you can get people to associated diaphragmatic breathing with correct movement, it can also be a very helpful strategy for maintaining good control as you move into high level activity where movements are too fast to have a conscious core control strategy.
- As soon as you reasonably can, incorporate movement (especially segmental spine movement and rotation/lateral movements) into their exercise routine. Get them breathing through the movement and focusing on balance and control vs “stability.” Watch for signs that their motor control isn’t ideal: breath holding, asymmetry, and substitution patterns are big red flags for this!
- Don’t forget that in addition to conscious control, the core needs to have anticipatory control and reactive control-so add in higher level activities, unbalanced surfaces, etc. as needed to facilitate this.
We have an awesome opportunity with every patient that walks through the door-we can teach them movement patterns that will be functional and serve them well throughout the rest of their lives. I would challenge you to think beyond “stabilization” when it comes to neuromotor retraining! As an aside, you may notice that many of your patients who report stress incontinence or pressure during exercise report a decrease in these symptoms-hooray for unloading the pelvic floor and preventing more severe future problems!
Abboud et al. Effects of muscle fatigue, creep, and musculoskeletal pain on neuromuscular responses to unexpected perturbation of the trunk: a systematic review. Frontiers in Human Neuroscience. 2017 epub.
Diamond et al. Trunk, pelvis, and hip biomechanics in individuals with femoracetabular impingement syndrome: strategies for step ascent. Gait Posture. 2018: 11.
Park WM, Wang S, Kim YH, Wood KB, Sim JA, Li G. Effect of the Intra-Abdominal Pressure and the Center of Segmental Body Mass on the Lumbar Spine Mechanics – A Computational Parametric Study. Journal of Biomechanical Engineering. 2012;134(1):11009-NaN. doi:10.1115/1.4005541.
Stokes IAF, Gardner-Morse MG, Henry SM. Intra-abdominal pressure and abdominal wall muscular function: spinal unloading mechanism. Clinical biomechanics (Bristol, Avon). 2010;25(9):859-866. doi:10.1016/j.clinbiomech.2010.06.018.
Tavashi et al. Causal effect of intra-adominal pressure on maximal voluntary hip extension torque. European Journal of Applied Physiology. 2018:118(1). 93-99.