Posture is more and more becoming over-looked, especially in the “pain science” world.
If we find someone has pain in their spine it is important to consider posture or spinal biomechanics could be a causative or contributing factor. Furthermore, when looking at someone with knee, pelvis, shoulder or hip pain it is important to assess their spine.
Many suffer from altered posture and biomechanics of the spine due to genetics, conditions, pathology, pain, past injuries or repetative or sustained lifestyle habits which could contribute to pain, that is in fact "explained".
What is ideal posture?
There is no such thing as the perfect spine. Our postural type is determined by our genetics (Seaha et al) including i) our collagen which influences our flexibility, ii) bone density, iii) the integrity of our spinal discs, iv) our pelvic and hip bony structure, and v) our developmental milestones (Cil et al 2005). Postural control and balance within the spine appears to be an unconscious response moderated by neurocontrols to keep us within our base of support.
The Roussouley Classification (Roussouley et al 2005) collected imaging on thousands of people with asymptomatic spines and suggested four common types of spinal posture exist in the population i) long kyphosis (5%) ii) flat back (23%) iii) well balanced (37%) and iv) hyper lordotic (25%) . Czaprowski et al 2018, also suggested sway back was another.
In regards to the degree of curvature, there are broad averages within the population. The inwardness at the low back (lumbar lordosis) should measure approximately 32-56 degrees (L1-L4), the outwardness at the mid back (thoracic kyphosis) should measure approximately 26-46 degrees (T4-T12) and inwardness at the neck (cervical lordosis) should have a head offset on average 83 degrees (spino-cranial angle) (Bernhardt et al 1989). "Hypo" refers to less than the average and hyper refers to more than the average. When looking at the spine, there is a lot of variety out there, the most important factor in whether posture is linked with pain lies within spine balance and whether the pelvic-spinal curvatures are harmonious.
A spine that is balanced refers to one where the ear lines up with the back of the sacrum (which is bone at the base of our spine which attaches to the pelvis), as well as the back of the shoulder, back of the knee and back of the ankle. The other important factor in whether posture is ideal is whether the pelvic structure (pelvic incidence) matches our spinal curvatures, that is the pelvic incidence and lumbar lordosis are within 10 degrees of each other. A close correlation between the pelvis and spinal curves, specially lumbar lordosis, is ideal as it is a mechanism for the body to position its centre of gravity. More to the point, what this all means is that an ideal posture is one that is ergonomically advantageous while standing/ walking and mechanically effective and efficient while completing tasks of daily living (Kendall).
What is not ideal?
Aside from common structural variations including scoliosis, scheuermanns hyperkyphosis, and degenerative scoliosis, there are many cases in which the primary curves of the spine do not fit the "common"/typical in some way. It is important to remember the clinical presentation of juveniles/ adolescents with non-structural versus structural disturbances of body posture may be similar, it is more obvious in adults as the spine becomes less flexible. If the patient is able to change these postures with spinal movement (repeated at least 3 times for accuracy and when not limited by pain) it means they are not structural, and instead are "functional" postural variations that are amenable to change.
If we notice a rib prominence in forward bend such as in Idiopathic scoliosis, no improvement of hyper-kyphosis in extension such as in Scheuermann’s hyper -kyphosis, then there is a structural variation. If you on observation or radiographically notice i) the spine off-balance more than 2cm ii) the pelvic position does not fit the overall curvatures of the spine, iii) they have developed compensatory postures, iv) they have pain with repeated movements or sustained standing or sitting, then it may be good to explore further.
For the therapists out there, relaxed standing radiographs can give us fallible information if used in conjunction with a good physical assessment!
Pelvic incidence is a fixed clinical measure of sacral orientation in the pelvis. The close correlation between pelvic incidence and lumbar lordosis is a mechanism for the body to position its centre of gravity. The more sloped/ tilted toward perpendicular our sacrum is the higher our pelvic incidence. The higher the pelvic incidence the greater the lumbar lordosis, this often predisposes to hyper-curvature of the spine and that is normal for that person. The lower our pelvic incidence, the lesser the sacral slope/ the more horizontal and the more inclined toward hypo curvatures, and again that is normal for that person. Average pelvic incidence is 55 deg +/- 10 deg (Schwaab et al 2012). Posture is considered ideal when the pelvic incidence and lumbar lordosis are within 10 degrees of each other. When there is a mismatch of >10 degrees, there is a correlation of pain (Schwaab et al, Smith et al). In the case of spinal balance, postures are considered ideal when the plumb line (ear to back of S1 vertebrae) are aligned when standing within 2.5-5cm (SVAO). Where there is >5cm off balance there is an increase in pain (Smith et al). This is when posture is not ideal. Therefore, the ideal spine is one which is balanced, the spinal curvatures match the pelvic incidence, and the length-tension relationships of muscles at front and back and sides (agonist and antagonist musculature) are equal. Adults with spinal deformity more likely to end up having pain and functional issues due to postural changes are those with a pelvic tilt of 20 degrees or more, pelvic incidence mismatch of >10degrees and off balance central plumb line >5cm (Tarran & Shwab et al 2013).
For those who do not have standing imaging to refer to, try observation with anatomical landmarks to get an idea.
Stand in a relaxed posture. Do a quick scan of the body. Start with side on. Notice the curvatures of the spine, where they are located and how they look?. Check where the head, shoulders, hips, and ankles are - they should line up. Check whether the tailbone is quite pronounced or perhaps quite flat - this gives you an idea of sacral slope and whether their spinal curvatures fit their sacral slope. If there are hyper / exaggerated spinal curvatures then expect a pronounced tailbone, and if there are hypo spinal curvatures, then expect a flat tail bone pelvis parallel to floor. If there appears a mismatch, then it is worth investigating. Look at the spine from front on. Then look at their postural control under load and with movement tasks.
How is posture linked to spinal pain?
Each of the altered postures can disturb the physiological loading of the musculoskeletal system in a specific way, which may lead to a functional disorder, even though there is no “pathology”. Researchers now widely recognise links between mechanical loading and the biological responses of human tissue. Long before structural “pathology” (for example, disc herniation), changes are occurring in tissues as a result of mechanical loading (Smith et al 2008).
Understanding that even slight changes in posture or the biomechanics with compromised posture may affect efficiency and how we load structures, is an important indicator of the need for early intervention in postural correction (Sparrey et al). Poor posture and spinal mechanics is usually due to poor stamina of our muscles that hold us up against gravity (local and global spinal stabilisers), and/or poor cooperation of these muscles and our active movers (mobilisers). If the muscles designed to hold us up against gravity do not have enough stamina as they are weak/atrophied/ under active (hypotonic) then the muscles designed to move us take over and become reduced in flexibility and overactive to provide support (hypertonic). This can create tension/ discomfort and even pain, as well as increased load on our joints, ligaments and discs.
Another reason could be deficits in awareness of body in space (proprioception and neurocontrol). These have been correlated with spinal deformities in growing children (Lowe et al 2000, Cil 2005). In terms of changes in posture and biomechanics with age, we lose intervertebral disc height and hydration, they become less spongy, and in response to things we do in our daily life, often less forgiving. The cartilage in our joints also thins and we end up losing some height and feeling a bit compressed. Twin studies (Batisa et al 2009) have shown that genetics plays the biggest role in whether we will have pathology in our spines or not and that this is not directly related to environmental factors!. Types of postures can predispose us to certain types of pathology (Czaprowski et al 2018). How? Well, the load distribution in our spines directly effects where degeneration occurs most (Stokes 1976). Excessive or abnormal mechanical loads may lead to adaptations in the tissues of the spine (Stokes et al 1976). We know that a decreased inwardness in the low back (lumbar lordosis) and increased outwardness/ hunching in mid or low back (thoracic and lumbar kyphosis) are hallmarks of an ageing human spinal column along with decreased spinal flexibility (Terran et al 2009, Sparrey et al 2014).
The ability to compensate for altered posture or pathology will determine whether or not we have pain. Healthy individuals employ unconscious postural correction strategies to maintain balance for tasks such as running, lifting, bending, squatting and sitting. I mentioned above that disharmonious posture is correlated with pain, as is being off balance (>5 cm). But sometimes our body can adapt and deal with this well, while others cannot. Those with a lesser ability to compensate for natural age related postural change develop altered/ compensatory postures to stay upright. In patients with postural deformities, the strategies to compensate for a loss of balance that are consistent across individuals.
How do I improve my posture?
Most people will not need to correct their posture, but where posture is the likely contributor to pain and disability it needs to be addressed. The body is such a wonderful adapter to our lifestyle changes and ageing, but in some cases, it cannot adapt quickly enough, or perhaps it doesn't know the strategies and we much teach it. A more individualised and specific approach to spinal management is warranted for those with back pain.
Correcting posture is not as simple as teaching the spine to become straight. Remember the massive variation in the population in spinal posture!! They are all common types! When planing corrective exercises, it is important to ensure the exercises are based on i/ the individual evaluation of posture, especially when the posture does not match one of the common types mentioned, and ii) the analysis of the posture in the usual sustained or repeated positions for the person (Czaprowski et al 2018). Therefore the program is individualised, specific and functional for them.
Improvement of one’s posture is cued through elongation, ribcage expansions and forward/backward/ sideways rotations and translations as these cause significant changes in the spinal curvatures (thoracic kyphosis, lumbar curve, and pelvic tilt and scoliosis) (Deed et al 2002).
Consideration of all the muscles in the trunk is required. Restoring the length of muscles is important, referring to whether their shortened or lengthened. Bergmark and Richardson et al indicate that muscle lengthening may not be related to muscle weakness but can be analyzed in respect to its over or under activity (hyper- or hypoactivity). When our inner supporters are weak, our larger muscles designed to move us become overactive and decreased in flexibility to provide much needed support. Under activity (hypotonicity) is common in the local stabilisers and overactivity (hypertonicity) is common in the global stabilisers/ mobilisers but this isn’t always the case.
We should not necessarily strengthen one and stretch the other, but rather reduce activity through regaining the activity of the stabilisers, in this example, the gluteus maximus, and through strengthening both muscles in the corrected posture and the range in which they're weak (Bergmark).
Special consideration especially in adult spinal deformity should be given to maintenance of lumbar lordosis and conditioning of the deep paraspinal muscles (deep and superficial). Don't stop here! The muscles that hold us upright and hold our joints together (local stabilisers -multifidus, transverse abdominus, interspinalis, semispinalis, internal oblique, diaphgram and pelvic floor) and (global stabilisers- trapezius, erector spinae, glutes and adductors) and the active movers (mobilisers -rectus abdominus, external oblique, quadratus lumborum, psoas, hamstrings, qaudrciceps) must cooperate to allow for appropriate transfer of load during functional activities.
Once correct posture can be achieved and controlled through movement it is important to integrate into functional exercises including squatting, sitting, standing and walking and any other activities relevant to them.
If you have recurrent/ persistent spinal pain that is due to pathology or "yet to be explained", it is important to see a therapist who has an understanding of posture and spinal kinematics. This includes someone who knows how to i) assess spinal posture and your biomechanics, especially those of your sport of choice, ii) correct dysfunctional postures, iii) condition the muscles of the trunk (all of them), and then iv) integrate these postures with control into their desired activities/exercise/sport.
This forms the basic methods I incorporate when investigating, treating and managing spinal pain as a physiotherapist.
References
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