Applying Dynamic Neuromuscular Stabilisation (DNS) to common barbell squatting faults
The problem: Poor squatting architypes propagated by dysfunction breathing patterns and a lack of intra-abdominal pressure.
The article is split up into: introduction, physical faults, explanation of intra-abdominal pressure, and finally application to common faults.
Squatting has become the go to exercise for most gym goers, but unfortunately it is not as simple as we would like. Walking into any commercial gym there will be at least three guys/girls squatting with horrific technique, slowly counting down the days until a blown disc/career-ending knee pain. Even observing some of the professional fitness models/physique competitors, subtle but dangerous errors can be identified which leads to the question – why are even coaches teaching this simple movement incorrectly?
When done correctly, the squat is a safe and highly effective way of training nearly every muscle in the body. Squatting is not just a strengthening exercise, squatting in fact incorporates a number of different bodily control systems. As you unrack the barbell, it becomes a freely moveable object, which means YOU have to stabilise it. Perceived instability forces the neurological system to coordinate smaller stabilising muscles that lay close to joints to perform the task of neuromuscular stabilisation.
Learning to coordinate these small integral muscles can prevent future injuries by maintaining joint health. This is why overtraining the leg press machine is a bad idea. Leg pressing is a “unidirectional externally stabilised movement” – you can only push one way and you don’t need to stabilise the load, so you only train the “prime mover”. Too much strength in the prime mover can theoretically pull your joint out of its central position (centration) and lead to microtrauma; which is why focusing on these smaller stabilising muscles is so important for longevity in training.
Unfortunately throughout our life we all pick up bad movement habits: mid-back slouching, pulling shoulders forward, anterior pelvic tilt, pronation of the foot, knock knees; we could go on. These postural faults show us that our bodies are innately lazy and follow regular dysfunctional patterning. We will always pick the path of least resistance.
When developing any high-level motor skill, we pick up on subtle technique errors by consistently auditing movement patterns, with the view of progressing towards increased efficiency. Most of us need to take an ego check and start over again if we want to be successful in skill acquisition.
Part 1 – Physical faults/Positioning
Centre of mass and the mid foot
Understanding what we should be doing while squatting means we need to understand the behaviour of the weight in relation to gravity. Once you understand this, you will be able to effectively coach yourself. First we need to get some terminology out the way:
- Centre of mass: the area in which all the mass focuses, as the barbell becomes heavier the COM will become considerably lower;
- Mid-foot: this is the sweet spot, the exact midpoint between your toe and your heel;
- Fulcrum: the axis of rotation (ideally the hip joint);
- Bar path: the movement of the bar as viewed from the side (most commonly);
- Moment arm: The distance between the fulcrum and the load
There are two rules within barbell training “the COM stays over the mid-foot” and “the bar path should be vertical at all times”. These basic principles are HUGELY simplified in order to give an overview.
High bar vs low bar with relation to the mid foot
The main issue for casual gym goers is bar placement. Our natural instinct is to put the bar high on the shoulders which, as you lower into your squat, means the weight will deviate significantly from the mid-foot creating a huge shear force across the spine (a much larger moment arm) and an increased space between the fulcrum and the weight – most probably a sore low back too.
This happens when we have a high bar placement with low bar mechanics. When squatting high bar, we expect a closed knee and ankle angle with an open hip angle, creating a more upright torso which keeps the COM over the mid-foot. These high bar mechanics are unnatural for beginners, thus what we often see is a closed hip angle, with more open knee and ankle angles, leading to a more horizontal torso, thus pushing the COM away from the mid-foot.
To rectify this, we need to either reprogramme the high bar motor pattern or move the bar further down the back into the low bar position. The low bar position will negate or reduce the excessive sheer stress created by having the bar too high up the back.
Looking at the two pictures, we can see by placing the bar further down the back, we can keep the COM much closer to the mid-foot, creating a more fluid vertical bar path, bringing the fulcrum closer to the COM and increasing the amount of weight that can be lifted.
Part 2 – Biomechanics and intra-abdominal pressure
Your back is not particularly happy when being forced to bend under heavy load, spines (when loaded) prefer to be locked in a neutral position. Patwardan AG (2000) found that the cervical spine, when loaded in a flexed posture, was able to resist 40N of pressure. However, in “spinal neutral”, the cervical spine can resist loads of up to 250N. Your spine is made of vertebrae, separated by discs, with smaller facet joints located posteriorly. When spinal alignment is maintained, the back is an incredibly resilient structure. However, when even the smallest “kink/malalignment” appears, we predispose ourselves to injury. If you are lifting any type of weight with a bent spine, you are most probably increasing the chance of a serious spinal complaint (for most beginner/intermediate level lifters, the Chinese weightlifting team seem to be including a lot of loaded spinal flexion).
Intra-abdominal pressure and the diaphragm
Imagine an empty cardboard box – easy to crush when you push on it. Now inflate a balloon in it – almost impossible to crush now.
Our lumbar spine is a sultry projection that joins the pelvis to the ribcage, it looks incredibly precarious in contrast to the large pelvic basin and 360 degree bony structure of the ribcage. However, the lumbar spine can be stabilised a lot like the cardboard box.
When you take a deep breath into your abdomen you create “intra-abdominal pressure” (IAP) which is similar to the inflation of a balloon in a cardboard box. The deep breath fills the abdomen and pushes outwards against the core muscles, creating an incredibly strong lumbar spine. This is why the inclusion of a belt at heavier weights is something worth investigating. The belt creates even more force for the intra-abdominal pressure to push against, I do not believe it creates any weakness or atrophy of these muscles (articles).
Types of breathing dysfunction; respiration and the diaphragm
The diaphragm has two main jobs – respiratory and postural. We will first examine the respiratory function.
The diaphragm is a large sheet muscle that transverses the bottom of the thoracic cage; it creates a muscular dome between the lungs and the abdomen. The muscle spans from the xiphoid process (sternum) all around the costal margins (ribs) inserting onto T12 (spinal column) there is a large central tendon that runs from the crest of the dome.
There are a number of “holes” or apertures in the diaphragm, the oesophagus being one of the most relevant for us (more on this later). As the diaphragm contracts it pulls downwards, lowering the pressure in the thoracic cage, thus pulling in air fresh for respiration. This movement is performed on average 30,000 times per day and I cannot emphasise enough how important this is – if you gave a client an exercise to do 30,000 times per day, you would make damn sure they did it properly. So why do we neglect to teach our clients proper breathing habits? Most probably laziness or ignorance. Correct diaphragmatic mechanics will not only effect respiration, but also the ability to generate IAP.
Faulty breathing patterns: Chest breathing
Chest breathing, you have most probably heard of it, but do you really understand it? Can you assess it properly? And do you understand how it can relate to lower back pain, neck pain, and even possibily gastrointestinal reflux?
Chest breathing is an acquired fully integrated subconscious motor pattern. There are a number of aetiologies in my opinion, most prominently poor postural function such as desk work. A desk worker's posture (thoracic kyphosis, scapula protraction, glenohumeral internal rotation, forward head carriage) sets the scene for the diaphragm to switch off; by pre-activating the accessory, and at the same time placing the thoracic cage in downward rotation (thoracic kyphosis), you literally force the diaphragm to switch off and the accessories to take over the moment.
Prolonged stress/anxiety can also lead to a chest dominant pattern. When stressed the body is conditioned to produce a “flight or fight” response, this is the body's way of getting ready for action. Blood pressure is raised (and shunted to muscles), pupils dilate, digestion stops and, importantly for us, the breathing rate increases.
As the breathing rate increases, the body utilises the accessory muscles, reducing diaphragmatic excursion. Our primitive stress response is designed for single transient events (eg, a caveman being chased by a lion). However, in today’s society our stress is less likely to be a single transient event, and more likely to be low-level stress over a long period (work). Physically this leads to maladaptive patterns, including high blood pressure and chest breathing.
Chest breathing utilises muscles such as the sternocleimastoid, scalenes, upper trapezius and pec minor to force the ribcage upwards.
Products of faulty breathing mechanics with relation to intra-abdominal pressure (IAP): the postural function of the diaphragm
The diaphragm's most relevant function to us is postural in nature. The IAP mechanism's integral lynchpin is conscious control of diaphragmatic excursion. The intra-abdominal pressure mechanism is a hydraulic amplifier, it is comprised of a number of muscles in the abdomen: diaphragm superiorly, transverse abdominis/internal oblique’s laterally, pelvic floor inferiorly and low back musculature posteriorly. Please note this list is not exhaustive, more details of exact musculature is easy to find, but does not concern our topic's overview.
Now, if you can visualise our 3D structure you can almost imagine it as a barrel full of grapes (not sure why we use grapes). Taking this analogy further, if we wanted to create maximal tension in our barrel (to crush the grapes) we would need the lid of the barrel to travel downwards into the barrel, crushing the contents, but more importantly creating maximal pressure across all aspects of the barrel (outwards pressure, pushing against the sides and bottom of the barrel).
The lid that travels downwards in this analogy is the diaphragm, it is the diaphagm that creates the tension in the IAP mechanism. We aim for isometric contraction in all muscles of the IAP except the diaphragm, which contracts concentrically (everything else is held still while the lid descends). So you can see why inhibition of the diaphragm in clients who exhibit chest breathing is such an issue when squatting! Their grapes are not squashed!
Clinical applications of faulty diaphragmatic activation
So here I provide three studies in relation to our topic. Firstly we will use a study from the Prague school of rehabilitation. This study, published by Pavel Kolar in 2012, assessed the excursion (movement) of the diaphragm in healthy (control) subjects against chronic back pain patients. Pavel found the chronic lower back pain patients to have significantly less excursion in their respiratory function of their diaphragm and less postural control, thus leading us to assume that chronic pain inhibits the function of the diaphragm and further compromises the stability of the lower back/core.
Next I have a study published in 2014 by Helen Bradley and Joseph Esformes. In this study the authors investigated the correlation between faulty movement patterns (assessed through the FMS, if you don’t know what that is I suggest you find out) and breathing pattern disorders (such as faulty diaphragm mechanics). The FMS (functional movement screen) is used to assess an individual’s movement capability and thus susceptibility to injury, and was developed by Gray Cook. The authors found a positive correlation between BPD (breathing pattern disorders) and poor motor control. The authors deduced that “poor diaphragmatic control could result in muscular imbalance, motor control alterations, and physiological adaptations that are capable of modifying movement”.
Finally and taking a slight detour, I give you a study on diaphragmatic control and GERD (gastinoesophageal reflux disease). We talked earlier about the holes (apperatures) in the diaphragm and we mentioned about structures that travel through the apparatures, one being the oesophagus. GERD occurs in brief, due to a ring of muscle in the lower oesophagus being too relaxed, allowing stomach acid to travel up from the stomach through the diaphragm into the oesophagus. This study showed an increase in the tone of the lower and upper oesophageal sphincters with appropriate postural control of the diaphragm.
So we can conclude correct use of the diaphragm is not just a hypothetical concept, but a clinically useful endeavour for us to pursue with our clients.
Applying the IAP to squatting faults
Very common in females (Instagram models particularly), allowing your back to overextend at any point will create a “hollow back” appearance, keeping your chest up is an unhelpful cue as it encourages these athletes to maintain an arched back. By loading in extension, your push the facet joints together (apposition), often leading to painful joint inflammation and fixation, which is often felt in the mid-back area. You also reduce your ability to fill the abdomen with 360 degrees of pressure as your ribcage has become dissociated from the pelvis.
Upwards rotation of the ribcage brings the diaphragm away from its optimal position, hugely reducing its capability to perform its postural function. The lid of the barrel cannot descend to create the maximal pressure needed. This type of dysfunction is known in dynamic neuromuscular stabilisation as “scissoring dysfunction” and leads to occult anterior instability.
In this picture, we can see the diaphragm's axis has become more oblique meaning the barrel of IAP is unable to swell out symmetrically, reducing the client’s ability to generate optimal IAP, also predisposing to anterior instability and posterior facet syndrome.
Butt wink – probably the single biggest squat fault which is highly debated. As with everything you read on the internet, take any advice with a pinch of salt. There is in reality no one way to do things, no absolutes, so instead with my knowledge of spinal mechanics (more correctly, Stuart McGill’s knowledge of spinal mechanics) we can only give an opinion.
The spine is being loaded and asked to cyclically undergo flexion/extension with butt winks, as we know the spine is made to move as a whole and segments are made to distribute movement across large areas. The butt wink creates movement focused on the lower lumbar spine alone (coincidently the most common area to blow a disc). This constant and repetitive flexion extension cycle is thought to chip away at the outer layers of a disc, theoretically predisposing to disc injury.
This dysfunction can be thought of to be opposite to hyperextension in many ways. In hyperextension fault, we angulate our ribcage away from our pelvic floor. However, in flexion, we angulate our pelvic floor away from the ribcage. As the pelvic tilts posteriorly, the transervse plane of the pelvic floor muscles are taken out of alignment with the now properly positioned ribcage and diaphragm, again impacting the barrel's ability to generate maximum force safely.
All opinions are my own and do not represent secondary parties.
Luke Thomas Neal
North Down Chiropractic
34 Grays Hill, Bangor
With thanks to www.rehabbs.com
Patwardhan AG 2000 “Load carrying capacity of the human cervical spine in compression is increased under a follower load” Spine, 25(12) 1548-54 http://www.ncbi.nlm.nih.gov/pubmed/10851105 [accessed 2/3/2016]
Kolar P, Sulc J 2012 “Postural function of the diaphragm in persons with and without chronic low back pain” J Orthop Sports Physical Therapy 42:352-362 http://www.ncbi.nlm.nih.gov/pubmed/22236541 [accessed 2/3/2016]
P Bitnar, J Stovicek, 2015/16 “Leg raise increases pressure in lower and upper oesophageal sphincter among patients with gastroesophageal reflux disease” J of Bodywork and Movement Therapies, in press. www.sciencedirect.com/science/article/pii/S1360859215002909 [accessed 02/03/2016]
H Bradley, J Esformes, 2014 “Breathing pattern disorders and functional movement” The International Journal of Sports Physical Therapy, 9:7 28-39 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3924606/ [accessed 2/3/2016]