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Breathing & Bracing pt. 2

By Michael Edgar

If you’ve been following along since part one of this two-part series on breathing and bracing, then I respect your fortitude for continuing along this muddy journey with me. If you haven’t had a chance to read part one yet, I’d recommend (clicking here) then coming back to this research review article.

Recapping where we left off, part one involved breathing physiology and mechanics, the mechanism of action and efficacy behind breathing techniques, mouth versus nose breathing, and sleep apnea. Part two aims to cover the musculature involved in breathing under load as it relates to bracing and the pelvic floor musculature (PFM), PFM’s apparent importance in relation to diastasis recti of the abdominal musculature (DRAM), and finally, various measurement techniques of DRAM and the current beliefs surrounding DRAM symptomatology.

You Want To “Activate” Your Diaphragm? Lift Weights.

To start this off, we’ll be looking at a study by the infamous, Stu McGill (1). In this study, they investigated the relationship between spinal integrity in relation to ventilatory demands, in regard to activation of torso musculature (1). They did this through an isometric versus dynamic loading task in which individuals were induced to increase ventilation through a 10% CO2 mixture (1). To make things a little more uncomfortable, participants had an intra-abdominal pressure (lAP) catheter fed down their oesophagus to the stomach and anchored with a nose clip (1). Generously enough, the investigators used a 2% xylocaine jelly to lightly anaesthetize the nasopharynx, although subjects were still unable to close their mouth (1). As a side note: surface EMG does not offer an accurate means to measure IAP. Although, an alternate pressure sensor can be used, which involves insertion into the rectum, so I guess, pick your poison (1-3).

Based on the current methodology, by not allowing participants to close their mouth and therefore glottis to induce breathing, IAP was roughly 10mmHg and rarely exceeded 50 mmHg (1). This is in stark contrast to IAP during typical lifting tasks with a closed glottis (Valsalva maneuver), in which these values are typically over 100mmHg and have been reported to reach 300mmHg during extremely heavy lifts (1-3). They found that during such activities, whether isometric or dynamic, the abdominal wall musculature only had minor changes to activation, while the diaphragm saw an almost two-fold increase in work output to sustain ventilatory volume (1). On a humorous note, it seems that to improve our diaphragmatic breathing ability, we just need to load people while they lift and force them to keep their mouth open.

Things get a little more complicated once we understand that the diaphragm acts as a multi-functional muscle involved in ventilation and postural control (4). Similar to the study above, participants were induced to hyperventilate through an elevated CO2 mixture while performing a repetitive shoulder activity (4). Although this is the case, the results showed that unlike abdominal musculature which prioritizes spinal stability, the diaphragm prioritizes ventilatory ability (4). Even though activation increased, the results showed diminished postural activity (4). During activities which require simultaneously high postural and ventilatory demands, it appears the diaphragm is overridden to prioritize ventilation, in contrast to the abdominal musculature which prioritizes postural control (4). Therefore, is increased activation a good thing, bad thing, or not important? Personally, I don’t have the answer, but I do believe humans have innately developed efficient means to handle coordination of multiple external and internal demands, which may not be as easy to change as simply cueing someone to breathe deeper into their belly.

The Pelvic Floor – The Mitochondria of the Core?

Now that we understand, to a degree, how the abdominal musculature and diaphragm work together, we can look to the research regarding the synergistic action of the pelvic floor musculature. This area of research has been popularized as therapists claim that appropriate activation of the pelvic floor requires one to maintain relaxed abdominal muscles. One study looked at the activation of the PFM during various exercises but the three to note are the abdominal test (partial sit-up), maximal pelvic floor contraction, and isolated PFM contraction, in which participants were told not to activate the abdominal muscles (5). The results were quite interesting as the abdominal test showed the highest levels of PFM activation, greater than the maximal pelvic floor contraction. In all tests, IAP stayed relatively stable also (5).

Now some people may say that the degree of activation does not matter, and it’s the ratio between abdominal muscle activation to pelvic floor activation that matters. That being said, even with the isolated pelvic floor contraction, activation in the abdominal muscles was seen and attempts to isolate PFM recruitment failed (5). In addition, this exercise only resulted in a 25% MVC of the PFM, in which requirements for strength training and adaptation are no longer met (5).

What does this mean? It shows that coactivation of the PFM during abdominal muscle exercise is inevitable and specific PFM cueing may be unnecessary. There may be more merit to simply cueing individuals to use both muscles instead of attempting isolation during simple exercises as IAP tends to stay relatively low despite the movement used. A small caveat to this study is that the highest variance in muscle activation occurred between subjects, but not between exercise trials for each patient (5). To build on this, four other studies looked at this phenomenon and found similar results (6-8). Two studies by Sapsford et al. manipulated spine flexion and extension, and seated or standing position in two different populations: individuals without a history of incontinence and those with a history of incontinence. In both, they found similar activation in the PFM and abdominal muscles (6-7). The third study found that when subjects, with or without chronic low back pain, voluntarily activated their abdominal muscles, it resulted in increased pelvic floor muscle activity (8). These studies further illustrated that the increase in pelvic floor pressure occurred before the increase in the abdomen pressure and therefore was not simply a matter of increased IAP, stating that this response is most likely pre-programmed (6-8).

Finally, a study by Thompson et al. looked at the muscle activation patterns in a highly specific group of symptomatic women during PFM contractions and a Valsalva maneuver (9). By this, I mean they used transabdominal ultrasound to identify women that depressed their bladder base when attempting to perform a PFM contraction who also had a history of incontinence (9). To be noted: you can have incontinence when elevating the bladder base too, but they did not include these individuals within study (9). The results of this study were very interesting. Symptomatic women tended to have higher PFM contractions at rest but lower contractions during a PFM exercise, although IAP was the same (9). In addition, symptomatic women had higher levels of PFM activation during a Valsalva maneuver despite the same IAP (9). A very interesting caveat of this study, noted in the discussion, was that after data collection, subjects were allowed to observe the direction of the bladder base movement on ultrasound; 62% of the women were able to perform an elevating contraction within one biofeedback session (9). Sadly, they did not follow-up if this truly changed symptoms such as incontinence though (9). My best guess is that it did not, as I previously stated, women with bladder neck elevation can still have incontinence.

Overall, these studies highlight that torso musculature, in conjunction with PFM activation, is potentially an automatic response. More so, that simply cueing someone will not change how their body recruits muscles in the region to any substantial degree, or at the least, we may need an ultrasound for biofeedback. Overall, it seems more complicated than we initially thought and a purely reductionist approach to symptom relief seems too simplistic at the given time (5-9).

Diastasis Recti of the Abdominal Musculature (DRAM) – A Gap in Knowledge

A discussion regarding the pelvic floor and abdominal musculature would not be complete without delving into the research surrounding diastasis recti of the abdominal musculature (DRAM). DRAM is the separation of the muscles along the midline of the abdomen, which typically involves widening and thinning of the linea alba (10-12). This widening results in an increased distance between the rectus abdominus muscles, increasing the inter-rectus distance (IRD) (10-12). The threshold to diagnose a ‘pathological’ DRAM differs in the literature but can be defined as greater than 2.7 cm at the level of the umbilicus (10-12). Other studies have defined DRAM as an inter-recti distance of greater than 2cm at the level of the umbilicus or 4.5 cm above or below the umbilicus (10-12). More so, some studies have considered widening of greater than 2.2-2.3 cm, as identified by ultrasound measurements, as pathological DRAM (10-12). It appears that even in the current literature, a set criterion point to diagnose the condition is nebulous.

Either way, the condition is typically seen in women during and after pregnancy, as the IRD increases as pregnancy continues (10-12). The incidence varies between 66% and 100% in the final trimester of pregnancy with rates of DRAM being approximately 53% post-delivery, within a 24-hour window (10-12). In the 12 months post-delivery, up to 36% of women have this condition (10-12). From a physiological perspective, it has been considered to be related to several factors, including the hormonal-based elastic changes of the connective tissues, mechanical stresses placed on the abdominal wall by the growing fetus, and displacement of the abdominal organs (10-12). Several risk factors for developing the condition include, multiparity (number of pregnancies), maternal age, childcare responsibilities, heavy lifting, and a higher body mass index (10-12). Anecdotally, many claim regular exercise prior to pregnancy and during the antenatal period seem to reduce the risk of developing DRAM and reduce the size of DRAM. Additionally, exercises are frequently prescribed to postnatal women who have DRAM in an attempt to reduce its severity.

Specific Exercises for Specific Conditions?

Based on the controversy around the topic, I looked into the literature regarding exercise utility for reducing DRAM. A study by Khandale et al. in 2016 found that exercise could reduce DRAM in postpartum women (10). All women had vaginal delivery, a diastasis rectus larger than 2 finger width (more information on this method later) and were willing to join in the study (10). In the study, the finger palpation technique was used, in which participants would lie with pillow beneath their head and feet, then perform a modified sit-up (10). The therapist would then palpate, with their fingers, horizontally on participants linea alba (10). Their aim would be for finger width to fit the distance between the internal borders of two rectus abdominis muscles (10). They performed a total of five separate exercises and overall, found a significant reduction of the IRD (10).

Perfect, isn’t it? Well, not exactly. There were some glaring issues with this study as no participants were blinded to the intervention, and all voluntarily signed up (10). Even worse, there was no control group. For all we know, this could have just been natural history and even if the exercises helped, was there anything specifically important about the ones prescribed? Or, is movement, in general, simply good enough (10)? Lastly, the finger breadth test has been questioned in the literature as a valid measure with potentially high risk of bias, a discussion I will build on later in this article.

Building from this, I found a systematic review on the topic, offering a more encompassing analysis on the efficacy of exercise for DRAM as a preventative method and rehabilitation technique (11). Eight studies were included, four studies examined interventions during the antenatal period to reduce the risk of developing DRAM, and four studies examined the effects of postnatal interventions (11). All interventions included some form of exercise (11). As alluded previously, measurement of DRAM varied heavily as three studies used digital or dial calipers, two studies used a tape measure, and two studies did not specify (11). As you can see, we already are running into some issues but to make matters worse, the inter-recti distance that was considered to indicate DRAM varied also.

In regard to DRAM prevention, exercise reduced the chance of developing DRAM and reduced the IRD compared to inactive individuals (11). Although this seems promising, they did not differentiate between individuals who had been active for long durations prior to pregnancy versus those who simply started exercise prior to pregnancy as a preventative measure (11). Therefore, this could simply be that individuals who exercise, in general, over longer periods tend to adapt and have stronger musculotendinous tissue. More so, they did not find that exercise during pregnancy improved the recovery time from DRAM when controlled for parity and mode of delivery (11).

In contrast, exercise as a rehabilitative method for DRAM seems to have insufficient evidence to draw conclusions regarding its applicability at the current time (11). That being said, exercise has been shown to have a multitude of other benefits, such as improved strength and cardiovascular health. Therefore, activity during this period should be encouraged. We may just need to change our narrative towards the goal of such exercises, prescribe exercises meaningful to the individual, and avoid suggesting that such exercise will reduce DRAM.

Measuring the Gap – “Measuring Something In Finger Units May Not Be Best”

The efficacy of the intervention is only as good as the measure used. By this, I mean that we can’t truly know if an intervention, such as exercise, is good for the treatment of DRAM without an appropriate measurement tool. Therefore, let’s take a step back and look at the research regarding the utility of various measurement techniques for DRAM. A systematic review on this topic investigated 13 articles and found six predominant techniques (12):the finger width method, tape measure, ultrasound, MRI , CT and arguably the gold standard, intra- operative measurements with a ruler (12). One major issue with the studies including the finger width method is that no standardization procedure was described (12).

In regard to the finger width method, poor agreement was seen between assessors (12). Although, when one assessor did the test then redid it at a later time, they tended to have slightly better reliability (12). This level of agreement was observed even when experienced physiotherapists did the measures (12). That being said, zero literature in this review had described the actual utility of the test to determine if someone has DRAM or the severity of the condition (12). At best, we simply know that different assessors tend to be poor when it comes to its standardized utility (12). Therefore, although this method is convenient, it does not offer an appropriate means to diagnose, let alone assess DRAM at the current time (12). Things get a little worse when we look at the utility of the tape measure in diagnostic accuracy for DRAM, as it has been shown to have very poor ability to detect the condition compared to intra-operative tape measurements or CT scan (12).

When calipers were used and compared to ultrasound, both techniques were found to have relatively good levels of agreement, although this was only seen above the umbilicus (12). When measures were done below the umbilicus, systematic differences of 0.74-1.43 cm were found (12). Although this may not seem large, considering a diagnosis of DRAM by some definitions can be made at 2cm, this is a gross difference (12). Overall, there appears to be a lack of standardization in palpatory methods such as utility of calipers, tape measures and the finger width method, which in turn, despite clinical feasibility do not offer great means of assessment (12). Given this, it appears in a clinical setting, digital calipers may offer the most pragmatic approach when measuring above the umbilicus. However, ultrasound technology has improved to the point that handheld devices are available on the market (12). Therefore, if one is truly aiming to specialize in this area, it may be best to invest in the appropriate technology and education for ultrasound reading.

DRAM Pathology – Another Form of Over-Medicalization?

At this point, we know DRAM is a common experience regarding pregnancy, the birthing process, and the post-partum period. It has been postulated to be associated with adverse health consequences, such as lumbo-pelvic instability, low back pain, and incontinence (13). A systematic review investigated this topic, looking at the presence of DRAM, in relation to low back pain, lumbo-pelvic pain, pelvic pain, incontinence, and pelvic organ prolapse (13). The review included 12 studies, with a total of 2242 participants, of whom 229 were controls and four were males (13). Five of the studies used the finger-breadth measurement to determine presence of DRAM (you now know my pet peeve with this assessment method) (13). Measurement of DRAM was recorded during a curl up contraction or in a resting position, showing further variability in the measurement technique (13).

Although this is the case, they found no relationship between DRAM and lumbopelvic pain, low back pain or pelvic girdle pain (13). More so, they found no relationship between DRAM and incontinence, although a small association was found between the presence of DRAM and pelvic organ prolapse (13). Therefore, my final question based on this literature is: Is DRAM something we need to demonize or is it simply an adaptive response? I tend to air on the side that our bodies are resilient and gatekeeping someone’s entry to exercise and movement, simply due to a widening of abdominal tissue is doing more harm than good for that person. Look at the person in front of you, not their questionable diagnosis, and find activities that are best suited to their lifestyle and goals.

Take Homes

1. Abdominal and diaphragmatic muscle recruitment tend to be predominantly outside our conscious control.

2. The diaphragm prioritizes ventilation while the abdominal musculature prioritizes stability when both systems are simultaneous challenged.

3. Stop trying to recruit the pelvic floor muscles without the abdominal muscles.

a. All you’re doing is activating all of them less.

4. Exercise may be an appropriate preventative strategy for DRAM but its utility in its rehabilitation is questionable.

a. Don’t worry though, exercise has a lot of other benefits.

5. Exercise specificity for DRAM doesn’t seem to matter.

a. Instead, focus your exercises on what the person likes.

6. The finger width method for measuring DRAM is poor at best.

a. Although convenient, you’re better off with digital calipers or ultrasound.

7. DRAM is not a life-sentence to low back pain, pelvic pain, or incontinence… It’s not even related. However, there may be a small relation to pelvic organ prolapse.



1. McGill SM, Sharratt MT, Seguin JP. Loads on spinal tissues during simultaneous lifting and ventilatory challenge. Ergonomics. 1995 Sep 1;38(9):1772-92.

2. McGill SM, Sharratt MT. Relationship between intra-abdominal pressure and trunk EMG. Clinical Biomechanics. 1990 May 1;5(2):59-67.

3. Blazek D, Stastny P, Maszczyk A, Krawczyk M, Matykiewicz P, Petr M. Systematic review of intra-abdominal and intrathoracic pressures initiated by the Valsalva manoeuvre during high-intensity resistance exercises. Biology of Sport. 2019 Dec;36(4):373.

4. Hodges PW, Heijnen I, Gandevia SC. Postural activity of the diaphragm is reduced in humans when respiratory demand increases. The Journal of physiology. 2001 Dec;537(3):999-1008.

5. Neumann P, Gill V. Pelvic floor and abdominal muscle interaction: EMG activity and intra-abdominal pressure. International Urogynecology Journal. 2002 Apr 1;13(2):125-32.

6. Sapsford RR, Hodges PW, Richardson CA, Cooper DH, Markwell SJ, Jull GA. Co‐activation of the abdominal and pelvic floor muscles during voluntary exercises. Neurourology and Urodynamics: Official Journal of the International Continence Society. 2001;20(1):31-42.

7. Sapsford RR, Richardson CA, Maher CF, Hodges PW. Pelvic floor muscle activity in different sitting postures in continent and incontinent women. Archives of physical medicine and rehabilitation. 2008 Sep 1;89(9):1741-7.

8. Kahlaee AH, Ghamkhar L, Arab AM. Effect of the abdominal hollowing and bracing maneuvers on activity pattern of the lumbopelvic muscles during prone hip extension in subjects with or without chronic low back pain: a preliminary study. Journal of manipulative and physiological therapeutics. 2017 Feb 1;40(2):106-17.

9. Thompson JA, O'Sullivan PB, Briffa NK, Neumann P. Altered muscle activation patterns in symptomatic women during pelvic floor muscle contraction and Valsalva manouevre. Neurourology and Urodynamics: Official Journal of the International Continence Society. 2006;25(3):268-76.

10. Khandale SR, Hande D. Effects of abdominal exercises on reduction of diastasis recti in postnatal women. IJHSR. 2016;6(6):182-91.

11. Benjamin DR, Van de Water AT, Peiris CL. Effects of exercise on diastasis of the rectus abdominis muscle in the antenatal and postnatal periods: a systematic review. Physiotherapy. 2014 Mar 1;100(1):1-8.

12. Van de Water AT, Benjamin DR. Measurement methods to assess diastasis of the rectus abdominis muscle (DRAM): a systematic review of their measurement properties and meta-analytic reliability generalisation. Manual therapy. 2016 Feb 1;21:41-53.

13. Benjamin DR, Frawley HC, Shields N, van de Water AT, Taylor NF. Relationship between diastasis of the rectus abdominis muscle (DRAM) and musculoskeletal dysfunctions, pain and quality of life: a systematic review. Physiotherapy. 2019 Mar 1;105(1):24-34.

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