Matters three states. Despite it being the least dense of all, gas (or, air) is a powerful thing. Both the pressures held to keep our body upright and the gases exchanged to keep our bodies going are intimately interwoven. Air moves in and out of our lungs to fuel and exhaust our cellular machine, and with it the pressures of our thorax and abdomen are effected. Both the driving muscles of respiration and core stabilization have a significant overlap, and with this there exists a complex connection between respiration and our bodies ability to hold itself up and against the challenges of our environment.
Our human body has and can be described as a torso with five limbs, the neck being the fifth. From a gestalt, ten thousand foot view of our selves we could simplify the situation and states that we are built to move via these limbs (push, pull, reach, press, look, leap) around and through our torso. In order to give our limbs sufficient leverage, our torso/middle must be held sufficiently stable.
Although by no means exclusive, one of the most obvious signs of the inability to ideally function at ones middle is low back pain (LBP). Unfortunately, LBP also happens to be a very common ailment for humanity, and statistically, we are not good at its long term management. In the western world alone LBP is cited as one of two most common causes of disability, the second being mental health (1). It is so common, it is estimated that 80% of us will experience it in our lifetimes (2). Think of it as the influenza of orthopeadic issues; debilitating, but for most only temporary, and for a few catastrophic.
Not only is LBP a common and debilitating issue, but it is also an expensive one. In addition to contributing to lost wages, large medical expenses and increased risk of other health problems (3), LBP is estimated to annually directly and indirectly cost the United States 100 billion dollars (4). Because of it being so common, debilitation and expensive, a lot of research and effort has been put into attempting to change the situation.
Now in order to find a solution, typically one must first understand the problem. To start, one must understand what the ideal function for the lumbar spine even is.
There have been various models over time offered as to how the human spine buttresses and stabilizes itself against gravity and the forces of living, and the one proposed by Panjabi in the last two decades (5) that is most widely accepted. He suggested there could be seen as three general interlinked subsystems that together contribute to spinal stability:
1. Osteoligamentous sub system (the passive support via bones, ligaments)
2. Musculoskeletal subsystem (the active support, their strength and endurance)
3. Central nervous subsystem (the timing of it all)
Panjabi then suggested that a breakdown in one or more of the three subsystems would result in unideal forces on the spine, micro trauma, injury, pain and or pathology. Thus far, this theory seems to have held true. A slew of research has been produced showing that individuals with low back pain have delayed timing of the musculature that stabilizes the spine when sudden loading occurs (6, 7, 8), as well as decreased endurance of their trunk musculature (9, 10). Armed with this insight, there came the hope that we could rehabilitate folks with LBP via progressively teaching them to activate the muscles of their abdomen and trunk, and couple this with limb movements and/or demands. This is what is known throughout gym and rehab clinics as core stabilization exercise.
But we should the ask….
JUST HOW HELPFUL IS TRADITIONAL CORE STABILIZATION TRAINING IN TREATING LOW BACK PAIN?
The answer may be “not very”.
A large study (11) looking at the available literature on the effectiveness of spinal stabilization on low back pain found it to be ineffective at reducing pain or disability in acute low back pain.
When low back pain was chronic, spinal stabilization exercise was shown to be more effective at reducing pain and disability compared to no care at all, or folks simply being given an educational handout. However, the same study found spinal stabilization exercise to be equally effective as manipulation and/or general exercise in aiding chronic low back pain. A few years later more literature had come out (12) reaffirming the same thing; in the long term it does not seem to matter if you do specialized traditional core stabilization or just general exercise (you end up in the same, not so good place).
So; whether we moved, are moved, or move with a splinting intent, it all seems the same.
Thus it seems that we understand how to help people in the short term, but obviously there are individuals and situations we are failing. Without a doubt folks with LBP are roughing their backs up, but apparently the current/traditional model of strengthening/ rehabilitating this are is just not sufficient. Perhaps this requires us to look at how we frame what we address.
ENTER ITRA-ABDOMINAL PRESSURE
Now core stabilization exercises teaching pre-activation of abdominal musculature with challenges to the trunk and limbs, but the thing is; it is not as if we are built to splint our abdominals at all times. We can be quite relaxed and yet still prevent our spines from buckling.
So what exactly provides this “soft stability”?
Enter intra-abdominal pressure. This is the perfectly timed and co-ordinated fluctuating muscular co-contraction of the diaphragm, pelvic floor and surrounding abdominals. Even at rest there is a low level resting tone to all of these muscles, and a constant gradient of pressure within our abdominal cavity. As we inspire, our diaphragm (the main muscle of inspiration) will contract, flatten and descend, drawing air into the lungs and thoracic cavity. In order to make room for the diaphragm descending and moving the abdominal contents (organs), the pelvic floor will descend as well and the abdominal wall expand via a control eccentric contraction. With exhalation the diaphragm returns to its domed resting position, as well as the abdominal wall and pelvic floor.
In this way there is a constant undulating wave of respiration that contributes to postural sway, aiding to hold the human body both steady and loose in order to react to the changing demands of the environment.
If there is an increase in demand in the body beyond routine sitting, standing walking, then increased trunk stiffness will be needed. This can be created via simply an increase in IAP. The main modifier of IAP is the diaphragm. Since the contents (organs) of our abdominal cavity are largely non compressible this can be done via holding the abdominal wall and pelvic floor isometrically taught as the diaphragm contracts, there by causing an increase in IAP. If even greater IAP is needed, the abdominal wall can tighten harder and concentrically contract (shrinking the abdominal cavity area further). Think of pushing on a ballon on all sides and you will get the idea.
Although one can learn to increase their trunk stiffness/IAP through training, IAP is reflexive; we cannot help but adjust it in response to loading. This is why lifting limits are placed post surgically on individuals who have had abdominal surgery; the strain of lifting more than 10lbs would stress the healing scar, and 25lbs would blow it open (13). You cannot avoid it. Even in a healthy, intact abdomen, the strain can be notable; if you want to intimately understand the relationship between respiration, IAP and ones core musculature, just get a decent cold (rhinovirus). Whether it is chronically sneezing, coughing or both, after a couple of days you will be sure to feel the effects on your abdomen.
In fact, a chronic cough is considered a possible risk factor for developing an abdominal hernia (14), and anyone who has had the unfortunate experience of a hernia or abdominal surgery knows the terror associated with an impending cough or sneeze when recovering from such a situation. The pressures one can build inside feel enormous when the wall has been breached.
Now, as stated, the main modifier of IAP in the human body is the thoracic diaphragm, and the manner in which it performs this function has actually been observed and measured in a laboratory setting. A study examined how the diaphragm and abdominal musculature responded to sudden, rapid limb movement in healthy individuals (15). What they found was that in all subjects the diaphragm contracted 20 milliseconds prior to the onset of any arm musculature, regardless of the phase of respiration they were in, and coincided with a co-contraction of the abdominal wall. The researchers observed that the diaphragm switched from being a breather to a postural stabilizer in order to best hold the subjects steady (it increased IAP). So; the diaphragm is programmed to aide in postural stabilization, not just respiration.
But what happens when there are significant dual demands for respiration and postural stability? To examine this the same researchers again performed this same study, but this time compared it to a situation where the subjects had to respire with more difficulty (16). What they found was that when the subjects began to have difficulty breathing, their diaphragms quickly switched back to its primary role as a respirator. The take home message; Our body will always prioritize air over keeping ourselves upright. We may crumble without sufficient IAP, but we will most certainly die without air.
So that is a brief look at how our trunk manages the dual demands of respiration and postural stability in normal folks without LBP, but we should ask; how does this differ from how folks with LBP breath/steady themselves?
The answer is; quite a bit.
RESPIRATORY & DIAPHRAGMATIC FUNCTION IN INDIVIDUALS WITH CHRONIC LOW BACK PAIN
Backed by the knowledge that the IAP is a major contributor to core/trunk stabilization, a group of researchers (17) set out to investigate if there were differences between how individuals with and without chronic low back pain breath during a basic lifting task. What they found was that individuals with chronic LBP across the board tended to perform lifting tasks with more air in their lungs than their healthy/pain free counterparts. In other words; They performed lifting activities hyperinflated.
A second study took it a step further, and actually observed the diaphragm in real time during a postural demanding task in individuals both with and without chronic low back pain (18). They essentially had two groups of individuals lay in a live MRI and measured the excursions of their diaphragms under three conditions; at rest and with a 2o second isometric arm and leg challenge. What they saw what that at rest there appeared to be no difference between the groups; their diaphragms behaved the same. However, once there was a challenge placed on their limbs, notable differences were observed.
In the chronic LBP group there were significantly smaller excursions of the diaphragm with respiration (the diaphragm splinted) compared to the healthy group. In addition to this there was an abnormal coordination of the diaphragm observed during inspiration w/both limb demand tasks in the LBP group. This abnormal coordination suggested increased sheer forces on the lumbar spine compared to the healthy group.
So there seems to be a difference in respiratory habits and diaphragmatic coordination between folks with LBP and without when performing strenuous activity, but is the link between respiration and core, trunk, postural stability deeper than that?
What happens when one has trouble with respiration? Do disorders, problems or diseases of the respiratory system have an effect on disorders of trunk stabilization?
It appears that yes, they do.
In fact, it has been shown that just by having respiratory disease, one is two times as likely to have low back pain than in the general population (19). This makes sense; if respiration is a significant driver/adjuster for IAP, then having less than ideal respiration would result in less effective trunk stabilization. This same study also looked at the association between the incidence of pelvic floor dysfunction (the floor of the core) and low back dysfunction and found similarly increased (2.5x in fact) correlations between incontinence and low back pain (19).
The take home from this is: if you can’t maintain the roof or the floor, the pressure cannot hold no matter how strong the walls are.
In fact, just by getting short of breath, one begins to actually behave as if they have low back pain. Researchers looked at the effects of inspiratory muscle fatigue on postural strategies, and whether this differs from individuals with and without chronic/recurrent LBP (20). What they observed was that’s individuals with recurrent LBP took very rigid postures in order to steady themselves, regardless of if they were out of breath or not. The healthy individuals, conversely, took a loose and coordinated postural strategy to steady themselves when at rest. However, once short of breath, the healthy individuals became posturally splinted, just like the LBP group.
So; getting short of breath seems to make you act like you have LBP, or, having recurrant LBP makes you act like you are short of breath posturally.
Now, this all seems to come back to the function of a major, central muscle in the human body: the thoracic diaphragm, our primary muscle of respiration.
DIAPHRAGMATIC ANATOMY AND FUNCTION
The thoracic diaphragm is an incredible, central and far reaching structure in our body. It can be described as two muscles in one (a costal and a crural portion), with a right and left side. Interestingly, the diaphragm is asymmetrical; the right diaphragm is larger than the left, with the right crural tendon insertion reaching lower on the lumbar spine than the left (21). This asymmetry is theorized to lead to predictable pulls and patterns on our body, much like the way gravity always pulls us back to the earth (22).
Now the thoracic diaphragm is a complex muscle with complex functions, three main ones in fact:
1. Respiratory; it is the primary muscle of inspiration.
2. Postural; it is the major modified of IAP, and has a direct pull on the lumbar spine.
3. Sphincter; it is a main component of our lower esophageal sphincter.
What dictates how well the diaphragm can fulfill its three major roles in respiration, postural stabilization and sphincter is its position. This is where we come to a concept known as the diaphragms zone of apposition (ZOA). This is the domed resting position of the diaphragm at full exhalation prior to the commencement of inhalation. The greater the domed resting state, the more effective pull the diaphragm has to draw air into the body. Essentially, the bigger the ZOA, the better. The picture below, does a good job of illustrating both an ideal ZOA (left and center) and an unideal ZOA (right).
In the situation in the CENTER, the diaphragm is supported to allow for an effective downward pull, driving pressure DOWN into the abdominal cavity (contributing to IAP), and effectively drawing air into the lungs. In addition to this, the diaphragms attachments to the spine in the CENTER is positioned so that the pull is directed upward, effectively decompressing the lumbar spine with every inspiration. With every breath we can effectively pressurize the abdomen and decompress the lumbar spine. Brilliant.
Conversely, in the situation on the far RIGHT, the diaphragm is not supported in an effective starting position/ZOA, and thus the pressure of its contraction is driven anteriorly, poorly contributing to IAP, and poorly drawing air into the lungs. In this situation, one will be force to recruit accessory breathing muscles in order to inspire (cervical spine, shoulder girdle). In addition, and very significantly, the pull of the diaphragm contraction during both inspiration and postural demands is no longer upward, but more anterior. This effectives shears the lumbar spine, much like what the researchers observed in the previously noted study (18).
Now what determines how big/ideal ones ZOA may be is the activity of ones abdominal wall; the abdominals serve to oppose the diaphragms pull on the rib cage during inspiration (23, 24)! How effective they are at this can be observed by the position of ones anterior/lower rib cage, and this is where we come to the concept of rib flare (see image below).
Flared ribs (the image on the right) are essentially the outward sign of a diaphragm unopposed by an abdominal wall. This appears consistent with the hyperinflated tendencies and flattened diaphragmatic position described in the the chronic low back pain population (17, 18). It should be noted that in a position of an effective ZOA, the abdominals have a better length tension (stronger pull). In the case of a flared rib cage/flattened diaphragm, the length tension is poor, and the abdominals will be effectively weaker. Think of a situation where your arms are in a awkward position attempting to lift something; it may be possible but it won’t work out well.
So that is the ideal position for both respiration and core/trunk stabilization via production of IAP, what are other components that make up ideal resting respiration? Most significantly, there is the rate, volume and quality of respiration.
At rest, our body is not burning much energy, and therefore needs the bare minimum in terms of oxygen and carbon dioxide exchange. Normal resting respiration is listed in the literature as 10-15 breaths per minute, but like ones BMI, normal is not always ideal. Ideal resting respiration rate is more a lot the lines of 8-10 breathes per minute. Remember, if your just sitting/standing there, you aren’t burning a lot of fuel. Hyperventilation (written about HERE), and breath holding are two common disorders of breathing rate and volume, and can wreck havoc on ones well being and durability if not addressed.
So that is the rate of respiration, we could then ask what muscles should drive respiration?
A general rule is that the diaphragm should do the majority of the work, and the accessory muscles of respiration(scalenes most notably) should only perform at a minimum to aide with inhalation via lifting the ribs up and out (24). Exhalation is mainly passive (at rest, with effort this differs), with the diaphragm and accessory musculature relaxing, allowing passive recoil of the chest wall to push air out of the lungs/chest cavity (24).
That is all good and fine, but often all we have is simple observation. So, what should resting respiration should it look like?
It is quite simple: the ribcage should expand circumferentially, and the abdominal wall as well. This should be able to occur independent of spinal movement (24), and without flaring of the lower ribs throughout the respiration cycle (meaning; ones abdominal wall is able to support and oppose the diaphragm). The rate and volume of this expansion and collapse will be based on the metabolic needs and postural demands of the moment. At rest, again, they are quite low, thus respiration should appear fairly gentle.
What one may want to glean from this is that both excessive accessory/thoracic respiratory habits as well as excessive abdominal breathing can be problematic. Yes, one can over belly breathe, but this is typically only seen when one has consciously practiced to do so. Many well intentioned practitioners from all walks of approaches have mistakenly taught individuals to “breathe diaphramatically” by simply pouching their bellies, while not actually correcting the position and action of the diaphragm at all. Essentially, unless a ZOA is effectively attained and held by an abdominal wall, the diaphragm cannot function as a respirator, no matter how much one would like it too. Again this returns to the position resulting in the ability for a structure to function.
With that being said, how should air enter and leave the body? As written about much more extensively HERE, respiration should be predominantly nasal. In and out via the nose, or, at the very least; in through the nose, out through the mouth.
So that is a brief summary of resting respiration, we then need to come to the meat of it all–
How should one respire with effort?
Arguably no different. One should be able to maintain trunk stability and respire all without sacrificing trunk/pelvic position, as well as the freedom of movement of your neck and limbs, all while maintaining full quality of movement patterns.
What will change is the amount of tone the muscles of the trunk will have to create in order to provide postural stability for the task(s) at hand. As seen in the previously presented research (15,16); as the demands for postural stability increase, the diaphragms ability to act as a respirator, and the abdominal walls ability to remain relaxed to allow for expansion will decrease, all in order to hold the trunk steady. The question is then, what exactly does this look like?
There are several components to consider, and we can start by asking–
How should the abdominals kick in?
Answering this question is likely beyond the scope of this article, in that a great deal has been written and debated about this, and currently it is quite controversial. Unfortunately, the answer seems to be; it depends. There is a camp that feels that the the deeper layers of the abdominal wall, pelvic floor and the diaphragm need to be trained to kick on prior to the more superficial layers (since this is what is often seen on studies in healthy subjects). This is often known as the abdominal drawn in maneuver (ADM). There is another camp that feels that although this might be what happens, it is difficult to teach this, and so one should just be trained to engage their abdomen and let the body take care of the timing. This is often known as abdominal bracing.
Regardless, there needs to be even, effective abdominal tone in order to support the lumbar spine and trunk in general from collapsing during challenges. Just like the walls of a ballon, the pressure needs to be uniform and sufficient throughout to maintain the pressure. It should be noted that abdominal bracing has been shown to be more effective at both stiffening the lumbar spine (25), as well as activating and strengthening the abdominals than the drawn in maneuver (26). The things is, like previously stated, the abdominal muscles are not need to be firing intensely at all times; only as needed, when needed.
Essentially, ones abdominals need to kick in on time, at an effect intensity, and they need to last as long as necessary to maintain the needed IAP of the moment.
RESPIRATION PATTERNING DURING ACTIVITY, EXERCISE, CHALLENGES
So that looked at the quality of abdominal tone that needs to occur in order to steady the trunk and support the ribcage against the pull of the diaphragm. But how should one breath when bracing during an activity? The answer again appears to be; it depends, but mainly, it depends on the activity. What follows is a very brief overview of a complex concept, that will warrant future writings of a great depth.
At times a physical demand is so intense that it appears best to not breathe at all. By drawing air into the lungs, and holding it while bracing ones abdonimals, a high level of trunk stiffness can be created. This is known as the Valsalva Manuever (VM), and it is considered unavoidable when performing heavy lifting to the level of greater than 80% ones 1RPM (27). Without a doubt known to all of us, VM works via tonically contracting both our diaphragm, abdominal wall and pelvic floor, allowing for a stable and high IAP to be held. There is controversy whether VM is dangerous in that it can lead to extremely high (but temporary) blood pressure levels, but currently the health risks of it remain unknown (27).
The complication really comes in when you need to do something more than once. After all, one will need to breath.
Timed Exhalation/Inhalation With Effort
When efforts are of a moderate intensity, and last longer than a handful of seconds or repetitions, respiration will need to be performed and the timing considered. One portion of respiration has been known, and recently shown to be highly effective at buttressing the spine, and that is exhalation, particularly that of forced exhalation. Although exhalation is a process that is primarily passive when the body is at rest, the abdominals (particularly our obliques and transverse abdominus) are our muscles of primary forced exhalation. They function to force air out out of the lungs! In doing this they also decrease the area of the abdominal cavity, effectively increasing IAP.
A great way to experience this is via blowing up a ballon, holding the ballon in one hand and your other on your abdomen. You will feel both the strain of you abdominal wall in the effort to push air out, as well as the amazing contraction that is required via your abdominal wall in order to do so. The value of incorporating blowing up ballons has been previously described in the literature (28), and for the interested warrants further reading.
In fact, forced exhalation has been shown to be highly effective at recruiting abdominal musculature (29), even more so than than abdominal draw in maneuver (30), and is equally as effective at stabilizing the spine with a sudden load when compared to abdominal bracing (31). This knowledge is nothing new, as martial arts has taught this for centuries. Forced exhalation is essentially the martial arts “kai”; the burst of air often accompanied with a cry or a shout that is so often heard in athletics. Previously misunderstood as an attempt to startle or frighten an opponent, it has always been a method of producing power in a movement.
In this way, when strenuous efforts are sub maximal, and repeated in succession, it is at times useful to train ones self to exhale with effort, and inhale with recovery. The thing is, the exhalation for effective strength will have to vary in size, as a full exhalation is often associated with relaxation, and can result in a loss of power. The use of forceful pushes of air while pressurizing the abdomen has been eloquently described by Pavel Tsatsouline (32), and is analogous to barreling down during a bowel movement (only in this case the pelvic floor is locked, to actually prevent one). Small bursts of air will escape as pressure is maintained with movement, but a full exhalation will not necessarily occur. The less strenuous the movement, the more air can escape, the more strenuous the activity, more air will have be kept in to maintain the needed high IAP. This is referred to as power breathing, and can be seen as a bridge between a valsalva maneuver and full respiration with easier activities. Note; power breathing will only work and be effective if there is an effective ZOA present to aim the pressure downward into the abdomen. Position is key!
Breath Entraining For Endurance
When activities are of an endurance quality, ingraining ones respiration with the movement being performed will be ideal to allow for the most economical locomotion (24, 33, 34). This is known as breath entraining, and is observed in many elite professionals performing their sport (24, 33). Examples are timing inhalation and exhalation with steps during running, as well as during phases of rowing. When the movement has to last for any length of time, efficiency and rhythm is key, and it is in this way that the link between locomotion an respiration is most clearly observed. But, again, the ZOA of the diaphragm must be obtained for maximal efficiency. It cannot be repeated enough.
Now it is not as if issues with attaining and sustaining effective IAP with durable movement patterns are exclusively seen in just problems of the local anatomy. The effects can and often are far reaching throughout our systems. Since our bodies are five limbs attached on our trunk, problems with the function of the trunk often effect the function of the limbs. Our parts do not often function independently of one another.
Ideally these things described should be reflexive in order to allow for effective reactions to the demands of life. However, these reactions may need to be regularly practiced to allow the habitual response to be maintained. Our bodies are always adapting, whether we like it or not, and it is our own responsibility to ensure our adaptations are of the kind we desire. No one ever said strong, durable athleticism was easy, or a birth given right. But, with great intent, and effective practice, it can be cultivated and owned.
The next time a world class athletic event is being viewed, do not simply observe and admire how the great athletes move, but listen to how they breathe with their movements. For them the efficiency is something more natural, for the rest of us, it may take more work to achieve.
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