How to sit properly

How to sit properly? Thousands of specialists are trying to answer this question. We all hear that sitting is harmful, and many claim that bending the body in a sitting position causes a herniated spine. What is the reality? While writing my book1, I analyzed the architecture of the human body and the mechanisms that are responsible for both static body positions and movement. I abandoned many established patterns based on classical anatomy in favor of an analysis of the structure and movement of the human bio-machine.

Lack of evolutionary adaptation of humans to long-term sitting in a chair

The chair, as a piece of utilitarian furniture, began to become popular in the Middle Ages. Previously, people used a deep squat, which is now called the Asian or Slavic squat. They sat for a short time on a tree trunk, on a stone, or chest when at home. The chest was a universal piece of furniture in ancient times. They probably also sat for short periods on other simple pieces of furniture and objects without a backrest. A variant of the chair in these and earlier times was a throne, a litter or similar piece of furniture used by rulers to emphasize the lofty office they held. Their subjects probably envied their comfortable and ennobling “royal position”. Today, when most people in the world have fulfilled their dreams of sitting on a chair with a backrest, it turns out that, unfortunately, it is harmful to health for the following reasons:

1. Lack of evolutionary adaptation of the structure and mechanics of the torso to sitting for a long time; and

2. Lack of evolutionary adaptation of the mechanics of the lower limb muscles to sitting for a long time.

The first factor is the inadequacy of the vertical structure of the abdominal-lumbar segment for sitting for a long time. This segment is labeled “B” in Figure 1. It does not have any reinforcement with a skeleton. There is only a flexible section of the lumbar spine, which itself needs stabilization with muscle tension.

Lumbar section of the trunk – no skeleton reinforcement
Figure 1. Lumbar section of the trunk – no skeleton reinforcement

The ring of peripheral muscles is responsible for the construction of segment “B” (Figure 2). It constitutes approximately 45% of the cross-sectional area of the trunk. Soft tissues along with internal organs that have no stabilizing function constitute another 45% of the cross-sectional area, and the flexible spine, which is mistakenly considered to be a column lifting the torso and carrying loads, constitutes about 10% of the surface area.

The spring of the peripheral muscles of the trunk - the abdominal-lumbar section
Figure 2. Circumferential torso muscles spring – construction of section “B”

Even though the ring of peripheral muscles constitutes less than half of the cross-sectional area of this section, with the correct muscular structure of the body and muscle efficiency, it ensures proper stabilization of the torso in a standing position. This allows you to keep your spine in the neutral zone of your torso. This is largely due to the very strong extensor muscles of the buttocks and legs, which transmit muscle tension from the ground to the top of the body (through the ground reaction force). At the front, the abdominal muscles perform the straightening function.

However, when sitting, the mechanics of the torso change significantly. By interrupting the continuity of tension in the rear myofascial tapes in the hip joints, the back muscles become drastically weakened while sitting. The main straightening function is taken over by the abdominal muscles. However, they also get tired relatively quickly in this position. Moreover, these muscles are very weak in many people. As a result, due to the action of gravity forces “F1”, and ground reaction forces “R1”, there is a constant compression of the lumbar spine section “B” (Figure 1). In the illustration, the upper limit of this pressure is marked by the rib line, schematically marked with line “b”, and the lower one, the upper edges of the pelvic bones, schematically marked with line “a”. Under the influence of these forces, the flexible spine undergoes uncontrolled buckling, which initially is small. However, they deepen over time and cause the destruction of its structure at the L5-S1 level.

The second factor is related to the lack of evolutionary adaptation of the mechanics of the leg muscles, including the buttocks, to stabilize the sitting position. It is the lack of this function that is responsible for interrupting the continuity of tension in the posterior myofascial tapes in the hip joints. It consists of the fact that the muscles of the buttocks and lower limbs in a sitting position are completely deprived of gravitational muscle tone. While sitting, gravitational tone affects only the muscles in the MT section (Figures 3 and 4), the lower attachments of which are located above the support of the two sit bones (point “A”). However, all muscles in the LMT section are deprived of activation muscle tension. Tension of the posterior myofascial chain occurs continuously throughout the entire height of the human body in a standing position. However, when sitting, the gluteal muscles and other leg muscles cease to perform the functions that determine body posture, and no longer function as back muscle extensors. This is why the back muscles are so weak when sitting. They are easily stretched, which contributes to slouching and contraction of the chest muscles and the back of the neck. This causes deformation of the entire figure, which becomes permanent over time. Not only does muscle deformation become permanent, but also the skeletal system becomes distorted due to long-term disturbance of their balance. This is especially dangerous in children, when the changes mentioned in the skeletal system occur very quickly and usually remain for life. The Delpech-Wolff’s Law2 describes the mechanism of bone weakening and causing serious skeletal deformities, including scoliosis.

Everyone can check the lack of muscle tone in the legs by palpation. When you sit down, the muscles in your legs relax from the feet to the hip joint, just as they do when a person is lying down or weightless. This condition results from the fact that the weight of the legs resting on the ground is so small that it does not cause any tension in the leg muscles. When you stand straight again, the muscles are firm and have a gravitational muscle tone that is transmitted to the other muscles above the hip joint, straightening the entire body and giving the muscles a useful initial tension.

When describing the lack of muscle tension in the legs while sitting, I would draw attention to a fragment of an article by Stuart McGill. He is a promoter of the so-called mechanics of the “hip hinge”, which was artificially created by him and his followers as one of the main elements of the human body mechanics. McGill suggested that hip hinge exercises can counteract the negative effects of sitting:

[…] Special exercises designed to combat the cumulative stresses from sitting are also usually helpful. Here, encoding the “hip hinge” movement pattern to replace the spine bending pattern is important. 3

This is not true. It is not possible to influence the way you sit with the hip hinge pattern or use special exercises for this purpose. This is because all the muscles that have their lower attachments below the sit bone are not active in a sitting position, including the “hip hinge” muscles.

Rather than omitting this statement, I have added a comment, because I consider the promotion of the so-called “hip hinge mechanics” is incorrect and harmful.

Other effects on the body resulting from the lack of muscle tone in the legs while sitting

Since the phenomenon of lack of muscle tension in the legs while sitting is completely ignored in the literature, I marked the zone in which it occurs particularly clearly in selected illustrations (Figures 3-4, 8-13). It is marked with the LMT dimension line – a turquoise horizontal hatching of the legs deprived of muscle tone, and a lightly dotted rectangle in the same color marking the height at which they are deprived of muscle tone. This was done to draw the reader’s attention to the lack of muscle tension in this part of the body while sitting. I believe that overuse of sitting over a person’s life has very serious consequences for the health of the lower limbs. These consequences are particularly visible in seniors.

Long periods of lack of gravitational tension in the leg muscles promote the degradation of blood vessels, malnutrition of the leg tissues, and systematic weakening of the muscles. There are significant analogies here to the state experienced by cosmonauts in a state of weightlessness on the International Space Station. Their bodies are constantly deprived of gravitational muscle tension, which results in accelerated tissue degradation and progressive weakening of the body. Therefore, they are subjected to specialized medical examinations before flights, as well as while in weightlessness, and after returning to Earth. The results of these studies indicate how devastating the permanent lack of muscle tone is for the body in people exposed to weightlessness. In terrestrial conditions, the lack of gravitational muscle tension in the legs while sitting is not continuous (a person does not sit continuously). This is one of the reasons why the degradation of body tissues in the legs takes a relatively long time. However, the consequences in the long run are as bad as they are in space. The longer a person sits during his life, the more the muscle tissue in the legs is destroyed by the lack of muscle tension. It seems that the statistics indicating a rapid increase in lower limb diseases from the mid-20th Century to the present day are directly related to the increase in the length of sitting during a person’s life.

How to sit properly –Upright sitting position

The upright sitting position (Figure 5) involves evenly supporting the sit bones by the seat plane and maintaining the torso in such a way that it is symmetrical to the main axis of the body in the frontal plane. In the lateral plane, this axis begins at the point of support of the body with the sit bone (point “A”), passes through the center of gravity of the torso, and through the center of gravity of the head located near the ear. A slight deviation from this rule in the case of the model in Figure 3 results from a slight forward leaning and a slight turning of the body to the right.

How to sit properly - upright position in the lateral plane
Figure 3. Steel spring and peripheral muscle spring of the torso – upright position
How to sit properly - upright position in the frontal plane
Figure 4. Steel spring and circumferential muscle spring of the torso – bent position
  • Figures 3-4
  • Ma – The main axis of the body
  • A – Trunk support points (sit bones)
  • F – Upper body gravity
  • R – Ground reaction force
  • MT – Muscle gravitational tone zone
  • LMT – The height of the zone without muscle tension in the legs
  • N – Outer contour of the muscles’ neutral zone

In the upright sitting position, the torso muscles are in a state of balance and the variable 3D axis of the spine is in the neutral zone. This sitting position is completely safe, but maintaining it for a long is not possible, among other things, due to the lack of support from the extensor muscles located below the hip joint. Hence, the position presented by the model is usually used only ad hoc. Its more useful variety is the so-called simple sitting using the back of a chair. In practice, it is also used to a limited extent, because it is not a sufficiently ergonomic position when writing or performing precise activities. These activities usually require greater visual concentration and proper resting of the hands on the countertop, which in practice forces the body to tilt. Therefore, when sitting, people lean, bend sideways and in various ways, and twist their trunks, using their habitual positions. They often enjoy these positions almost every day and for many hours. They are all harmful, and some of them are very harmful.

How to sit properly – a position with a bent torso

Is sitting with a bent torso acceptable? Many specialists stigmatize any bending in a sitting position as a pathological position, and some even say that it causes prolapse of spinal discs. Indeed, long periods of sitting are very harmful to the spine. However, not all bending of the torso while sitting is harmful. You can sit safely when bending over, provided its duration is short enough to not significantly weaken the abdominal-lumbar muscle ring, causing compression of the “B” segment.

Upright standing position - tension of the peripheral muscle spring
Figure 5. Upright standing position – tension of the peripheral muscle spring

However, people with a good physique can usually sit with their torso bent for longer (Figures 6, 8-10). They have strong, elastic muscles and a body structure that causes the variable 3D axis of the torso to be in the neutral zone – the spine is not subject to any loads. Figures 5 and 6 show an analogy in the way the steel spring and torso function in people with a perfectly shaped peripheral torso muscle spring. A person uses his body in many ways, such as bending during sports exercises, and in everyday activities. He often transfers this habit to a sitting position.

The “system of live muscle springs” shaped circumferentially along its entire height, from the pelvis to the neck (Figure 5), is responsible for stabilizing the torso, as well as for bending it in various directions in this position. When flexed, the steel spring acts mechanically in a similar way to the muscles surrounding the torso cylinder (Figure 6). It has its variable 3D axis (no. 1) just like the torso (no. 1S).

How to sit properly - tension of the peripheral muscle spring in a sitting position
Figure 6. Bent sitting position – muscle tone

Figure 6

1 – Variable 3D spring axis

1S – Variable 3D spine axis

 C – Compression zone

 S – Stretch zone

With the correct structure of the spring and trunk muscles, both axes are in the neutral layer during bending. On the concave side of these systems is a compression layer “C” and on the convex side there is a tension layer “S”. Although a muscle spring bends much like a regular spring, its mechanical system is much more complex.

It functions thanks to the mechanical transmission of the torso muscles. A diagram of how the gear works when bending the torso forward is shown in Figure 7.

Single segment of the trunk muscle transmission at the lumbar level
Figure 7 Single segment of the trunk muscle transmission at the lumbar level

Figure 7 Descriptions

1: Variable spine 3D axis – Neutral

2: Intervertebral disc — schematically

3: Spinal vertebra

4: The group of muscles around the circumference of the trunk

5: Abdominal soft tissues

6: Part of the muscle lever arm in the compression zone

7: Part of the muscle lever arm in the stretching zone

8: Single muscle fibers in the compressed zone

9: Single muscle fibers in the stretch zone

C:  Outer contour of the compression zone

S:  Outer contour of the tension zone

X: Y-Axis and A–B axis — inert layer

X: Linea mediana anterior

Y:  Line median posterior

You can read more about how the muscle spring that bends the torso under the influence of the mechanical transmission of the torso (spine) works and what conditions must be met for the variable 3D axis of the spine to be in the neutral layer in articles No. 6, 7 and 8 of my blog. For the proper functioning of the torso, the muscles do not have to be as clearly sculpted as in Figure 4. It is enough if the body structure is similar to the Gravitational Postural Pattern.4

Other examples of sitting with a bent torso are shown in Figures 8-10. Everybody in the illustrations above has a very good body structure and can sit in a bent position. However, their sitting time should be limited because even in their case, overuse of sitting causes fatigue of the abdominal and back muscles over time. If such a seat is abused, then over time the harmonious body posture is disturbed and the heavy upper body segments begin to fall inertly. This may cause partial displacement of the spine from the neutral layer and begin devastating pressure on the intervertebral discs and progressive destruction of the spine.

F 8 1 1 Easy 1 9. How to sit properly - Part I
Figure 8
Bent sitting position - a person with proper muscle structure, with excessive bending of the torso
Figure 9
Safe bent sitting position - a person with proper muscle structure
Figure 10

Figures 8-10. Bent sitting position – people with proper muscle structure

1 – Variable 3D Spine Axis

MT – Muscle gravitational tone zone

LMT – The height of the zone without muscle tension in the legs

C – Outer outline of the muscle compression zone

S – Outer outline of the muscle stretching zone

The position adopted by the model in Figure 9 is potentially dangerous. Despite her impeccable body structure and strong abdominal muscles, she adopted a position that, when sitting for a long time, may result in the loss of the above-mentioned muscle balance due to too much body tilt (bend) forward. The head and upper torso load the muscles maintaining balance with the force “F” acting on a significant eccentricity (arm “X”). The greater the inclination (the greater the length of the “X” arm), the faster the spring of the peripheral muscles of the torso weakens, which may cause the spine to shift from the neutral layer. The destructive forces resulting from the load exerted by the upper part of the torso then begin to act on its structures.

How to sit properly – incorrect body structure

Unfortunately, incorrect body structure increases the negative effects of sitting. Even if you try very hard, you cannot sit properly in this case. Prolonged sitting is especially harmful to people who have neglected to maintain a proper body structure or have never achieved it. The situation is made worse by the fact that, due to the progressive decline in the body’s efficiency, sitting is usually the main way of spending time for these people. This applies not only to their work but also to many other activities they prefer performing while sitting. The examples discussed in this part of the article concern common structural abnormalities that, unfortunately, are often accepted and considered by many to be the normal body structure.

Bent sitting position – people with abnormal muscle structure (obesity)
Figure 10
Bent sitting position – people with abnormal muscle structure (obesity)
Figure 11
Bent sitting position - a slim person with stretched abdominal muscles
Figure 12

Figures 10-12. Bent sitting position – people with abnormal muscle structure

1 – Variable 3D Spine Axis

MT – Zone of gravitational tonus of Meissen

LMT – The height of the zone without muscle tension in the legs

C – Outer outline of the muscle compression zone

S – Outer outline of the muscle stretching zone

Obese people. The men shown in Figures 11 and 12 not only have stretched back muscles, but they also have strongly pushed abdominal muscles. Although obese people sometimes retain quite strong abdominal muscles developed in their youth under the outer layer of fatty tissue, they are usually significantly stretched by internal fatty tissue and deformed viscera. The result of their weakening is the simultaneous excessive stretching of both the back muscles and the front wall of the trunk muscles. The proper proportions of the peripheral spring of trunk muscles are deformed and its mechanics are seriously weakened. There is an unfavorable shift in the setting of the variable 3D axis of the spine from the neutral layer with a simultaneous increase in body weight. This always causes deformation of the spine’s curvature and, during prolonged sitting, faster flattening of intervertebral discs and deformation of the articular surfaces of individual vertebrae.

Slim people. Muscle imbalance does not only affect obese people. Any neglect of proper body structure, even those that may seem inconspicuous, may adversely affect the health of the spine. An example is slim people whose abdominal muscles are so weak that they do not keep the abdominal viscera in the proper position. They are pushed out and stretch the weak abdominal coverings (Figure 13), deforming the most important part of the peripheral muscle spring of the trunk. Meanwhile, this part of it, when it creates the correct compression layer, is mainly responsible for transferring the loads from the upper part of the body to the pelvis. If the abdominal muscles are stretched, the spine is also partially displaced from the neutral layer, which accelerates its destruction.

Correctly identifying spinal mechanics while sitting

Modern science has not yet correctly recognized the mechanics of the human body. She also did not recognize the conditions related to long-term sitting.  Specialists from various fields prepare for us alleged improvements in our lives, filling it with both commercial attractions and improvements at work and in everyday life, very often failing to account for the needs of the human body and the effects they have on the health of the human population. This applies to a very large extent to the seemingly unimportant activity of sitting. They usually do not have the time or appropriate knowledge to take care of their client’s health. Medical science is also superficially interested in sitting and the mechanics of the spine. Scientists like to define the spine itself as a column that supports both external loads and the body itself. By greatly simplifying this issue, they get rid of the hassle of solving the problem themselves, leaving it to the patients. When discussing the mechanisms responsible for a person assuming a sitting position, I must once again correct these views.

The spine is not a column designed to bear vertical loads, as some scientists claim. The spine, when used correctly, functions as an extremely precise gear, causing variable tensions in the muscles proportional to the forces acting on them. In conjunction with the intervertebral discs, ligaments, muscles, and other structures that connect it, it works like the proverbial Swiss watch, ensuring the health of its user.

The spine is a structure responsible for straightening movements of the torso, straight bending, lateral bending, axial rotation, and all combinations of these movements, often performed simultaneously. It is composed of 33 bones, including 23 vertebrae separated by joints (intervertebral discs), which provide it with mobility and flexibility. Each vertebra has an individual structure and is equipped with two symmetrically positioned posterior articular processes. The spine itself has 92 articular surfaces that are directly responsible for its bending movements. However, its entire structure, from the pelvis through the ribs to the occiput, has a total of 364 small joint surfaces arranged differently in 3D space, which determines the mobility of the human body and the ability to perform dynamic movements, as well as those that are extremely complex and delicate. All these elements finely regulate the vectors of forces activating muscle tension in proportion to the forces acting on the human body.

However, such a complex, flexible mechanical structure is not suitable for serving as a pole or a rigid construction crane arm. The human biomachine operates thanks to a set of interconnected levers. One of them is the torso. However, this is a special lever. It has its own mechanism that allows it to change its 3D shape, adapting the structure of this lever to the weight being lifted, its location in space and the efficiency of operation of the other levers. The mechanical transmission of the torso muscles is responsible for adapting this shape and the muscle tensions that stabilize it. Improper understanding of the mechanics of the spine results in its misuse. This also applies to a large extent to the sitting position.​

When does prolonged sitting start to damage the spine?

The degree of maladjustment of the peripheral muscle ring to the lifted weight of the torso and the time during which the limit muscle tensions are exceeded determine the scope and speed of spinal deformation while sitting. This process begins in childhood, when prolonged sitting becomes dominant and, at this age, it can progress very quickly (scoliosis). The destruction of the structures of the mechanical transmission of muscles in many people often begins before they are fully developed. Sitting and spending time passively are starting to dominate earlier and earlier in a person’s life. This usually begins at the age of 5-6 (Figures 13,14 and 15).

Harmful long sitting - young people at school desks
Figure 13
Harmful long sitting - a child in a harmful tilt at the desk
Figure 14
Harmful long sitting - young people at the computer
Figure 15

This activity displaces and limits the natural hunger for movement in children, which is one of the most important mechanisms influencing proper human development. At this age, the body grows dynamically and ends around 18-20 years of age. If it is not accompanied by shaping the correct postural pattern and adapting the parameters of muscle strength to the acting gravity, the opportunity to create a strong foundation for the functioning of the body in adult life is usually irreversibly lost. In such a case, limited body fitness becomes visible in increasingly younger people. This is facilitated by a way of functioning that increasingly violates man’s evolutionary adaptation to living conditions. Some scientists believe that humans evolve and adapt to living conditions. However, research shows that people’s bodily structure has not changed for thousands of years. There is no indication that this structure will change in the foreseeable future because the way it is adapted is optimal for natural functioning on Earth. The extent of spine destruction in childhood depends largely on the more or less favorable circumstances of its development, as well as on the quality of the inherited by the child. Many people suffer from serious spine injuries at an increasingly younger age. When they start exercising at the gym or doing other sports activities, they don’t realize that their spine is no longer fully functional because it was seriously deformed due to prolonged sitting in childhood. They also don’t realize that this loss of efficiency progresses almost throughout their entire lifetime when they sit down for a long time.

How to sit properly – Active sitting

The harmful effects of sitting for a long time result from the inadequacy of the human body’s mechanics for this activity. Since our civilization has developed in such a direction that it cannot be eliminated, we should do as much as possible to reduce this harm Below is a quote from my book, which contains tips on how to sit properly.

[…] General rules for sitting:

  • Sit as little as possible, and spend any time saved on physical activity;
  • If you spend several hours sitting down, be sure to take breaks every 1-2 hours and stand up to regain muscle tone and circulation in your legs. Spend 5-10 minutes warming up your leg muscles and your entire body to start blood flow by doing short aerobic exercises, hops, bends, or squats;
  • While sitting, use a straight posture as often as possible, with the pelvis and shoul­der strap as parallel to the edge of the table as possible, without twisting the torso, pelvis, and other body deformities.
  • Vary your torso position from time to time, taking the spine temporarily from exten­sion to flexion, then to hyperextension, and back to an upright position. Active sitting improves the blood supply to the muscles of the torso and spine;
  • Every day, spend at least 20–30 minutes on exercises that compensate for sitting. This can be fast walking, aerobics, fitness, jog­ging, etc. Spend 60–90 minutes three times a week on your personal interval training, unless your doctor tells you otherwise.5

  1. Marian Jodlowski, Fix Your Back Like an Architect, Amazon 2022 ↩︎
  2. Wolff’s law, Wikipedia, You can read more about this law and its graphic interpretation in my book: Marian Jodlowski, Fix Your Back Like an Architect, subsection: Identification of Body Posture Defects Amazon 2022 ↩︎
  3. By : Dr. Stuart McGill, Empowering Self Advocacy: Taking charge of your back pain (2015), November 28, 2014, [Blog] ↩︎
  4. Marian Jodlowski, Chapter 7 – Human Gravitational Postural Pattern, Fix Your Back Like an Architect, Amazon 2022 ↩︎
  5. Marian Jodlowski, Chapter 13 – Muvement Patterns/ How to Sit Properly, Fix Your Back Like an Architect, Amazon 2022 ↩︎

Figures No. 13, 14, 15 were used as polemical quotations (Fair Use).  

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