Within our introduction to human asymmetry, we discussed how the systems of the human body; visual, auditory, respiratory, neurological, lymphatic, musculoskeletal and so on, are lateralised to the right. Simply put, we are right-sided beings.
To quickly recap, this right-sided bias (remember sided NOT handed…) is compounded internally due to the static asymmetry we see within the body. A larger right diaphragm with a thicker central tendon, a higher resting dome state supported by a liver underneath. In addition to more fibres and attachments to the spine, they are connected between one and two vertebras lower than the left. This asymmetry makes the right diaphragm concentrically effective for respiration, exceptionally good at exhalation phase.
We have a diaphragm that is physically pulling us to the right with each breath we take, occurring on average between 17,500 and 22,600 per day. That’s continual concentric pulling, breath after breath, lateralising the body repeatedly towards the right.
On the left however, the diaphragm is smaller in diameter, central tendon length and tendon width. It’s less able to effectively maintain it’s domed shaped due to the heart above creating downward compression increasing the “flattened” resting position of the diaphragm without the supporting structure below found on the right through the liver. This provides poor abdominal eccentric opposition for respiration and limits effective exhalation.
The left diaphragm has neither the structure or position to come close to preventing right lateralisation of the body compared to the power of 20,000 daily respiratory cycles.
This repeated pull of the diaphragm, effects our human skeleton due to this spine orientation towards the right. Pulling us into right stance, we develop increasing levels of lumbo-pelvic stability on the right. The pelvis and sacrum follows suit rotating right, with the left hemipelvis anteriorly tipping and forwardly rotating whilst the right hemi-pelvis acts in reverse.
To enable the body to remained centre for forward gait, the thorax compensatory orients back to the left to enable forward progression of the torso. This torsion of the body, right rotation below the diaphragm, left rotation above, influences the musculoskeletal system from head-to-toe.
We can expanded further with the concept when we consider that the left-hemisphere of the brain, our social/language dominant hemisphere, contralaterally controls the right side of the body. It leads to an over reliance of the right upper limb in social communication and interaction with the world (reaching, shaking hands, opening doors…) directing the body repeatedly into left trunk rotation from a position of right stance.
In human gait, the upper and lower limbs should work in opposition. As the left leg progresses forward the right arm moves into flexion contralaterally. At stance phase, the body should accept load fully onto the standing leg to enable swing phase of the opposite limb and contralateral arm.
Gait itself is a tri-planar action, involving sagittal plane progression, alternating frontal plane lateralisation below the diaphragm and transverse plane rotation above the diaphragm.
However, with this natural static asymmetry of the musculoskeletal and respiratory systems, we become favourable towards certain phases of walking. Right stance and left swing become dominant, or to give it a respiratory twist, right exhalation, left inhalation become dominant. Remember its not just a pelvis that moves during gait, its a ribcage.
Inefficient ribcage movement equals inefficient walking/running mechanics.
The muscle chains therefore of right stance become chronically overactive, as do those of left swing. We lack the capacity to effectively inhibit these chains to fully alternate back into left stance and right swing. Likewise we lack the capacity for full exhalation with a left diaphragmm, restoring its domed shape, and the alternating full inhalation of a right diaphragm to create the more flattened “pancake” shape of inhalation.
This impacts the way in which we feel and ground the body with the floor. Right stance creates a strong neurological reference of heel contact with the floor as bodyweight shifts posteriorly with lumbar rotation and pelvic torsion to the right. We become familiar and stable in the heel-strike/mid-stance phase of gait on the right side, one of the reason many of us favour a specific standing leg in single-legged exercise as we adapt to this loading pattern of stance. Whilst on the left we become more favourable to the explosive mid-stance/toe-off phase due to this positional influence of joint position on muscular function.
Runners that enter IFT will often present with similar patterns when screened on intake with assessments that measure the capacity to alternate between left and right, not only at a pelvis, but at the ribcage. They’re in many cases locked heavily into this pattern due to the long distances they run on asymmetrically right-biased mechanics. Compounding the 22,000 breathes taken each day pulling the individual into right stance. They are athletes limited to effectively one phase of the gait cycle and one phase of respiration.
Our job at IFT is to establish the dominance of this pattern, how it effects mechanics at the pelvis AND at a ribcage. We aim to develop the capacity to shift diaphragmatic function to the left, promoting full exhalation and competency for lateralisation to the left, anchoring with key muscles to maintain this function. Whilst simultaneously creating expansion of a right ribcage to promote alternating airflow.
We begin therefore to develop the capacity to counter the sequence of respiration we are pulled into every day by our natural asymmetry. Training couples this with facilitation of key muscles for left stance and right swing by coaching an individual to find and reference this muscles and positions in exercises, both ground-based and in standing.
This process aims to take an individual heavily patterned into mechanics of one phase of the gait cycle in both the pelvis and ribcage, and opens up the capacity to effectively alternate and reciprocate with lateralisation from the right side through right heel strike, mid-stance and toe-off, and propel fully onto left with transverse plane pelvic action and accept left stance load in the frontal plane without falling back into our heavily patterned, right-biased mechanics.
The natural asymmetry of the human body is beautifully designed to meet our function as beings that should move with variability in our actions, alternating and reciprocating. However with our tendency towards trying to deliver symmetrical training approaches, as well as our 21st century parafunctional habits, on an asymmetrical system, we create this often predictable imbalance. These patterns are neurological in nature, the brain will always win, it favours right lateralisation for survival, not necessarily for performance.
An understanding of human asymmetry and it’s impact on running mechanics creates a basis upon which to build efficient human movement that appreciates our uniqueness as human beings as bi-pedal animals with systemwide asymmetry.