yogabook / movement physiology / posture

Posture

As the only exclusively bipedal hominid, humans have undergone many adaptations to their skeleton and musculature compared to their predominantly or exclusively quadrupedal predecessors. These include, for example, the enlargement of the ROM of the hip joints (the original hind legs) and their anatomical standard position shifted by 90°, the differentiation of the hand into a versatile tool made possible by the relief of the arms (original forelegs) with the enlargement of the ROM of the associated limb joint (shoulder joint) and, perhaps the best known adaptation: the double-S shape of the spine instead of the C-shaped convex spine. Today this is designed in such a way that pyhsiologically the gravity perpendicular of the partial body weight of the arms with the head and upper body (at least close to anatomical standard position) runs through the connecting line of the two acetabuli, so that this partial body weight can be kept upright with a minimum muscular effort.

The skeletal geometry and muscular equipment are optimal for a person who predominantly works in a standing position. Today’s civilized life, however, suggests significantly different movement and posture patterns to people, for which they are not sufficiently adapted, or conversely, with their existing equipment they only remain stable in certain parameter ranges and otherwise have to accept side effects or compensate.

For example, sitting posture with a backrest that millions of people practise every day has many undesirable effects. First of all, hip flexion and knee flexion cause corresponding shortening of the hamstrings, most clearly in the monoarticular biceps femoris caput breve, as well as in the hip area, especially in the hip-flexing iliopsoas. Furthermore, the muscles that are supposed to balance the above-described partial body weight cranial to the hip joints, i.e. the hipflexors and hip extensors, tend to atrophy due to the lack of necessity for their work and thus lose their ability to cope with everyday situations other than supported sitting with ease or at all, so that the sedentary lifestyle is reinforced. But not only does the strength of these muscles diminish, their daily „working range“ (here we must actually speak of a lack of work) shifts from anatomical standard position by around 90°, and for many hours of the day no fraction of the ROM is used at all except for the one seated position, which leads to corresponding contractures, so it is no wonder if the office worker feels stiff at the end of the office day, without compensation he is stiff at the end of the day and becomes a little stiffer every day. In the leg area, the biarticular gastrocnemius should be mentioned, which is an important calf muscle for bipedal locomotion and also atrophies and tends to shorten. However, this behavior not only weakens the calf muscles, which are kept strong by standing and walking upright and ensure good venous return flow with the muscle pump and venous valves, but can also lead to contractures and restrictions in walking and running behavior as well as to shortening and weakening of the Achilles tendon, later on achillodynia and even rupture. This is followed by many disorders of the foot, which have the shortening of the triceps surae from the gastrocnemius and soleus as a risk factor and can in turn cause consecutive damage to the more proximal musculoskeletal system. A further factor is that the weakening of the above-mentioned muscles is also accompanied by the weakening of their tendons, so that there is a significantly increased risk of insertional tendinopathies or tendon ruptures, for example.

In addition to the effects on the lower extremities, the muscles of the trunk also slacken, as leaning against the back drastically reduces the need for their work. The autochthonous back muscles (erector spinae) and abdominal muscles as the most important postural muscles but also the most important moving muscles of the upper body, largely lose their competence, which in turn contributes to the reinforcement of the sedentary lifestyle. Depending on the exact position of the pelvis and the support of the back, this often leads to overstraining of the autochthonous back muscles accompanying the thoracic spine, which then usually manifests itself in a one-sided dragging pain next to the spine. The initially one-sided occurrence is a consequence of the frequently scoliotically altered back; due to side discrepancies, one side is predisposed to discomfort.

A closer analysis of sitting behavior often reveals a kyphosis of the lumbar spine, which occurs when sitting furniture is used without lumbar support or when this is leveraged by the distance of the buttocks from the backrest. Lumbar spine kyphosis is a massive risk factor for intervertebral disc problems. It causes and maintains them and repeatedly triggers the corresponding symptoms. Furthermore, many muscles of the autochthonous back musculature span several or many spinal segments, so that the wakening of the muscles of the lumbar spine kyphosis has a kyphosing effect on the thoracic spine. However, the kyphosis of both areas suggests compensation in the cervical spine area so that a reasonably upright posture of the head is possible and overexertion of the eye muscles is avoided. If a high screen resolution or a small display of the edited content or even just of the control elements adds to this, the head is pushed forward relative to the thorax, which almost completes the unpleasant full picture of the office worker. The combination of hyperlordosis of the cervical spine and head-forward posture that enlarges the lever arm predisposes to lasting disorders in the cervical spine and even intervertebral disc problems. The incorrect posture becomes really complete when the shoulder blades are also slightly elevated due to psychomental tension. The work performed by the levator scapulae and trapezius pars descendens then sooner or later causes painful tension in these muscles, and often also tension headaches originating in the neck.

The thoracic spine/shoulder/neck area is also often affected by the consequences of office work in other ways. Depending on the given parameters, orientation towards a VDU, nowadays mostly a computer, entails several risks and side effects. Manual operation of the common input devices mouse and keyboard tends to keep the shoulder blades in a certain protraction, which is additionally promoted by the convergent forearms and the slight internal rotation of the upper arms required when using a keyboard as an input device. The resulting redistribution of the body masses compared to standard anatomical position shifts the center of gravity forward, which is why all too often people compensate by means of hyperkyphosis of the thoracic spine so that the autochthonous back muscles are less strained. As people are usually more homo oeconomicus than homo exercitus, they avoid training their back muscles accordingly when doing so, which can be quite strenuous, and instead give in to the economy of sitting in a bowed position. The internal rotation of the upper arms also contributes to tension in the muscles that cause it, especially the deltoid pars clavicularis. If, on the other hand, the shoulder blades are habitually held retracted and a ridig effort is made to keep the upper body stretched, this can lead to a steep position of the thoracic spine in the long term.

If a shortening of the hip flexors is acquired through frequent sitting without compensating for the effects, this will also have an effect when standing if the shortening has reached a certain level. It is then no longer possible to hold the pelvis upright with the knee joints extended. This is all the more true if the muscular competence to do so in the form of sufficiently strong and enduring hip extensors is no longer present or was not acquired in the first place. But even with good competence, the hip extensors would have no chance of erecting the pelvis against contracted hip flexors, and so the person will inevitably stand with a hollow back. The person will give in all the more as the attempt to erect the pelvis would involve noticeable to massive effort.

If, in the physiological case of sufficiently strong hip extensors and sufficiently flexible hip flexors, it is sufficient to hold the pelvis upright with the hamstrings, their use alone will no longer be sufficient for a certain degree of shortening of the hip flexors, but the gluteus maximus must also be acquired, which the person is likely to perceive as unnatural. The hollow back when standing is also found when walking, as the push-off phase of the rear leg includes hip extension – if this was possible. Alternatively, the pelvis must be kept tilted forward, which leads to hypertrophy of some parts of the musculature in the lumbar spine area, which would not necessarily be pathogenic in itself, but the resulting hypertonus is.

It would provide relief in this respect if the knee joints were slightly bent, but this is usually not the case because the associated effort especially in the quadriceps is shied away from. After all, it is not necessarily strengthened or kept strong during largely sedentary activities.

The negative effects of predominantly sedentary activities include other phenomena. If this behavior is already present in childhood and adolescence, for example, the flexors and extensors of the knee joint will also remain underdeveloped, which can lead to compensatory hyperextension of the knee joint with weakening of the ligament structures when standing, which means joint instability of the knee. In addition, the habit of avoiding any effort of the hip extensors can develop, which is easily achieved by extending the hip joints, which leads to a clear and clearly pathogenic incorrect posture of the lumbar spine and, consequently, of the parts of the spine further up.

The back takes on a completely different relevance in a psychosomatic sense, regardless of daily posture, as for many people it is the first area in which stress has a physical impact. It is not for nothing that the rate of people presenting to their doctor with back pain of various kinds is so high. This is almost always at first a foremost functional and not a structural pain. The type of strain is highly variable and does not only relate to working life. Private life or aspects of it can also have a psychosomatic impact. It is also possible that the sum of the demands from different fields of life is greater than can be borne in the long term.

Many misconceptions are endemic in connection with the term hollow back. In many places there is a real fear of making a hollow back or having a hollow back. This should be clarified a little. In common parlance, a hollow back is the term for a hyperlordosis of the lumbar spine, i.e. it affects the area L1 to L5. A distinction must be made between a more or less permanent „habitual“ hollow back and a temporary hyperlordosis of the lumbar spine, for example for exercise purposes. The hollow back itself can be more or less pathogenic, depending on its extent and duration. A significant habitual hyperlordosis of the lumbar spine can, for example, lead to spondylolisthesis or spinal stenosis, both of which can cause neuroradicular symptoms, i.e. pain radiating down the leg, numbness or sensory disturbances and even motor deficits. The tone of the back muscles can also increase to such an extent that the pressure on the intervertebral discs is chronically increased, especially in conjunction with kyphosis of the lumbar spine, as is often the case when sitting, which will sooner or later lead to structural damage (discopathies such as disc protrusion or herniation), which can also cause neuroradicular complaints.

The hollow back is often the result of or associated with shortened hip flexors, which tilt the pelvis forward (at the top). Without eliminating the causative shortening, the hollow back is unlikely to be alleviated. On the other hand, hyperlordosis of the lumbar spine, for example in the context of a head-up dog pose, urdhva dhanurasana (back arch) or setu bandha sarvangasana, is not capable of causing any damage to a back that is not already massively damaged. It will, however, increase the tone of the lumbar spine-accompanying autochthonous back muscles a little, so that the performer may seek compensation.

For many people, it is not easy to feel whether they have/make a hollow back in any posture. This applies to sitting and standing or walking, but even more so to more unusual postures, especially if they involve hip flexion and extension of the back. If it is possible to palpate the spinous processes with the fingers of one hand, it is easier to make a statement. If the spinous processes protrude (visually or palpably) from the back, it can be assumed that the opposite of lordosis is present, namely kyphosis. If they do not protrude visibly, there are still many possibilities: a steep position of the spine, a physiological lordosis or a hyperlordosis. If the pelvis is now tilted alternately in both directions in the hip joints, it can usually be assumed that there is no hyperlordosis up to the point at which there is a noticeable increase in the tone of the muscles of the lumbar spine. If you go back a little from the point at which the noticeable increase in tone occurs in the direction of the straight back, you will find the physiological lordosis, or if you do not want to assume a single exact angle as physiological, the interval that can be regarded as physiological with a blurred edge. This method can be used in most postures and is also practicable for people with even less pronounced body awareness.