Natural Postures: Preserving Adaptive Potential

Introduction

Sedentary behavior refers to low energy expenditure while sitting, reclining, or lying down during waking hours. It is not the same as physical inactivity: a person can exercise regularly while spending much of their day sitting [1, 2].

This distinction matters in computer-based work. Sitting can suit certain tasks, particularly those that require precision or visual and manual stability. However, when it is prolonged and rarely interrupted, it becomes part of a set of behaviors associated with adverse effects on metabolic, cardiovascular, and functional health [1–4].

The available data do not allow us to claim that a specific sitting posture automatically causes disease. Rather, they indicate that a high amount of sedentary time is associated with an increase in certain risks, particularly when overall physical activity is low. World Health Organization guidelines therefore encourage adults to limit sedentary time and replace part of it with physical activity of any intensity [1, 3, 4].

From the Ideal Posture to the Capacity to Adapt

This article draws on a central concept of the SBNFA™ — Systemic Biological Neuro-fascial Adaptive Framework: adaptive potential, that is, the full set of options available to a person, in a given situation, to change their postural organization and vary the loads on their tissues, without losing balance or concentrating those loads over time.

In the SBNFA™ framework, a natural posture is not a fixed shape: it is a body configuration in which the body retains a capacity for adjustment, load redistribution, and active regulation [33].

1. Postural Adaptability

In the SBNFA™ framework, adaptability is the integrating concept. It has two complementary expressions: postural adaptability, addressed first here, and tissue adaptability. A sensory, informational, and proprioceptive loop contributes to adjustments across both, without constituting a third form of adaptability.

A Posture Is Never Completely Still

The human body never holds a posture in a perfectly static way. Sitting or standing is accompanied by small shifts in the center of gravity, changes in muscle activity, and constant sensorimotor adjustments [5, 7].

Postural control depends on integrating visual, vestibular, proprioceptive, and cutaneous information. Information from the soles of the feet, the joints, and the soft tissues helps, in particular, to estimate the body’s position and regulate balance [5, 7].

In this framework, postural adaptability refers to the capacity to change the body’s organization according to a task or a constraint. It does not mean maintaining a single alignment. On the contrary, it allows the pelvis to change orientation and weight to shift from one side to the other. It also makes it possible to change joint angles and to break off a position that has become uncomfortable.

Studies on postural control support components of this analysis [5]; adaptive potential, however, is a Blue Portance construct, for which they do not provide a validated measure.

Contemporary research on postural control shows that movement variability is not necessarily “noise” or a control error. It can reflect the capacity of the neuromuscular system to explore different solutions and adapt to constraints [6, 8].

2. The Limits of Prolonged Sitting

Sitting generally reduces postural muscle activity compared with walking or standing. When this position is held for a long time without interruption, lower-limb muscle activity remains low and certain circulatory parameters may be adversely affected [9, 10].

Experimental studies have shown that breaking up sitting with short periods of walking or light activity can improve certain metabolic and vascular markers compared with continuous sitting [10–12]. These effects do not mean that any given break would be optimal for everyone, but they support the value of regularly interrupting immobility.

The study by Healy and colleagues showed, in particular, that the frequency of breaks in sitting was associated with a better metabolic profile, independently of total sitting time in some observational analyses. Other work has shown that short breaks in sitting can reduce post-meal blood glucose spikes in adults at metabolic risk [11–13].

However, these results should be interpreted with caution. Experimental studies are often short, protocols differ, and the benefits observed on physiological markers do not always allow us to conclude that chronic disease is directly reduced.

From a musculoskeletal standpoint, exposure duration, workstation setup, task repetition, and psychosocial factors all interact. Prolonged sitting may be associated with low back pain or discomfort, but it is not, on its own, a sufficient explanation for all spinal pain [14, 15].

3. Variability of Positions

Standing generally makes it easier to change points of support and increases lower-limb muscle activity. Sit-stand desks can reduce sitting time and improve some musculoskeletal symptoms in the short term, but effects on productivity and long-term health vary depending on the equipment and how it is used [16, 17].

For example, standing is therefore not an ideal posture. Prolonged, static standing can also lead to fatigue, low back discomfort, or overload of the lower limbs. Its value depends mainly on the ability to walk, shift weight, and alternate with sitting [18].

Adaptive Positions: Varying Rather Than Imposing

Squatting is a functional position in many activities close to the ground. It strongly engages the hips, knees, and ankles, while changing how loads are distributed between the lower limbs and the pelvis. However, the range of motion required and the ability to hold this position depend on joint mobility, strength, age, and health status [19].

There is insufficient evidence to claim that squatting is universally beneficial for the spine, the pelvic floor, or the pudendal nerves. Squatting should therefore be considered an option for postural variation, not a treatment.

Kneeling and sitting on the floor also offer different configurations. They may encourage more frequent transitions in some people, but they can increase stress on the knees, hips, or ankles in others. Thus, the relevance of a position depends less on its label — natural, dynamic, or traditional — than on how well it is tolerated. It also depends on the ability to leave it easily.

Comparison: Prolonged Sitting vs. Alternating Positions

4. Pelvic Micro-Movements

The pelvis helps transmit forces between the trunk and the lower limbs. When sitting, it is not a fixed block: small variations in tilt, rotation, and weight shifting normally accompany movements of the trunk and upper limbs [20, 21].

These adjustments can change how pressure is distributed between the ischial tuberosities, the sacrum, and the gluteal tissues. Dynamic seating systems aim precisely to preserve some of these movements, without compromising the stability needed for work [22, 23].

Studies comparing dynamic seats, exercise balls, and conventional chairs do not allow us to conclude that instability is always beneficial. Some devices increase muscle activity or trunk movement, but this increase does not automatically translate into less pain or a lasting improvement in posture [22–24].

A seating device should therefore be evaluated on several criteria: freedom of pelvic movement, stability, pressure distribution, the fatigue it generates, and compatibility with the task. The goal is not to make the user unstable, but to allow them to change position easily.

5. Mechanotransduction and Fascial Tissue

Biological tissues respond to mechanical loads through structural and biochemical changes. Mechanotransduction is the process by which cells convert mechanical forces into intracellular signals that can change their activity [25, 26].

This principle is well established in several tissues, including bone, muscle, cartilage, and connective tissue. However, it does not allow us to claim that a specific posture would automatically restore the properties of fascia or prevent chronic pain.

Research on fascia describes interactions between the extracellular matrix, fibroblasts, mechanical loads, and sensory information. A recent review proposes, in particular, molecular mechanisms that may contribute to how fascial tissue responds to mechanical loads, but this literature remains largely mechanistic and does not yet allow precise postural recommendations to be derived [26–28].

6. Pudendal and Cluneal Pain

Pudendal pain is classically described as pain located in the territory of the pudendal nerve and aggravated by sitting. The Nantes criteria include, in particular, pain in the anatomical territory of the nerve, worsening when sitting, no objective sensory deficit, and relief from a diagnostic nerve block [29].

Sitting can therefore be a major aggravating factor for some patients. Historical clinical descriptions also report improvement when moving to standing or lying down. However, the fact that pain is triggered by sitting is not enough to distinguish pudendal neuralgia from myofascial, coccygeal, joint, skin-related, or pelvic floor pain [29, 30].

Management of pudendal pain remains heterogeneous. It may include measures to reduce mechanical stress, appropriate physical therapy, medication, injections, and, in some cases, interventional treatments. Available guidelines emphasize the need for a gradual, individualized approach [31, 32].

There is insufficient clinical evidence to claim that squatting systematically widens Alcock’s canal or decompresses the pudendal nerve. Likewise, a donut-shaped cushion is not necessarily appropriate: it may reduce central pressure for some people, but its effects depend on its design and how it redistributes loads.

In an ergonomic approach, it is better to look for the configurations the person tolerates best, reduce continuous sitting periods, and avoid positions that reproduce or increase symptoms. This approach does not replace a clinical evaluation when pain persists or is accompanied by neurological, urinary, digestive, or sexual symptoms.

7. Toward an Ergonomics of Variation

The purpose of a workstation is not to hold the body in a fixed configuration all day long. It is to allow a realistic alternation between sitting, standing, moving around, and changing points of support.

Sit-stand desks can help reduce sitting time, but their effectiveness depends on how they are used. An adjustable work surface is only useful if the person actually uses it and can alternate without creating new stress on the shoulders, neck, or lower limbs [16, 17].

Similarly, dynamic seating can encourage certain micro-movements, but it should not become a source of instability or fatigue. The best solution is often the one that strikes a balance between support, freedom of movement, and voluntary control of position.

Finally, walking is a simple strategy for breaking up sedentary time. A short activity between two tasks, moving around during a call, or a screen-free break can be enough to interrupt continuous sitting. The benefits depend not only on exercise intensity, but also on how often breaks occur and how well they fit into the real organization of work [11, 12].

Summary: Goals and Solutions

8. How Aporia® Makes Adaptability Possible While Sitting

The previous sections lead us to reframe the question: it is not about finding the right posture, but about evaluating what a position — or a seat — allows the body to vary, stabilize, and adapt on its own. Applied to sitting, this is the role of adaptive potential.

The SBNFA™ framework places natural postures in perspective with four organizing principles of living systems — motor variability, tissue flow, segmental independence, and autonomous regulation — then translates these principles into seven observable functions and 19 variables used to evaluate seating devices [33]. The first of these functions is preservation of the subject’s adaptive potential: the subject initiates and directs their changes in postural organization, and the seat follows them without blocking, steering, or replacing them.

Two questions are distinguished. The first concerns the governance of movement: who initiates it, chooses its direction, and controls its amplitude, speed, and stopping point. The second concerns the mechanical resolution of the interface: does it respond to very small adjustments, without an excessive threshold, dead zone, notch, or dominant return force? A seat that moves is therefore not necessarily a seat that preserves adaptive potential [33].

The Aporia® Architecture

This is the framework within which the Aporia® architecture fits. The Aporia® ExoBase is a curved, mobile base carrying four articulated, mechanically independent pads — front right, front left, rear right, rear left — each with its own foam and its own cover. The curved base follows the movements of the pelvis, while the four pads preserve the local origin of the loads and allow differentiated responses between the right and left sides [34]. The framework thus describes a continuous space of balanced oscillations up to ±45°, within which the person can move from one stabilized position to another without having to maintain an imbalance imposed by the seat [35].

This architecture seeks to answer the questions raised above: the person remains the source of their own adjustments, one side of the pelvis can act without moving the entire seat, and a local load can receive a local response.

What We Know — and What We Don’t Know Yet

For now, these properties rest on an expert-based, non-instrumented evaluation, conducted on the basis of documentation, expert opinion, and observation of how the device works. Applied to the Aporia® ExoBase mounted on the Boréal–Aporia prototype, which is not yet commercially available, and to five dynamic seats on the market, the grid gives the prototype a comparative score of 3.75 out of 4, compared with 1.76 to 2.62 for the five comparators [34]. This score evaluates the capacities offered by the architecture, not how a given person uses them.

The framework also documents the limitations of this architecture: horizontal displacements and spine–pelvis pivoting are largely allowed, but bounded by the geometry of the assembly; pressure distribution depends on body type, adjustment, and cushion version, and targeted offloading can shift part of the load to other areas; firmness cannot be adjusted separately on each pad [34]. Experimental measurements are scheduled with the GIBOC laboratory of the Institute of Movement Sciences in the first half of 2027 [35].

9. Conclusion

Natural postures are not a category of automatically beneficial positions. Standing, squatting, kneeling, sitting on the floor, and walking have different mechanical characteristics, but each can become a strain if held too long or if it does not match the person’s capacities.

The most important factor is variability. Being able to change the orientation of the pelvis, shift support areas, alternate levels of muscle activity, and regularly interrupt sitting broadens the body’s options for adaptation.

In the case of pudendal, cluneal, or pelvic pain, reducing aggravating positions may be relevant, but no posture can be presented as a universal treatment. The most cautious approach combines monitoring symptoms, gradual progression, workstation adjustment, and clinical evaluation when needed.

A posture is not necessarily healthy because it is natural, nor harmful because it is seated. It becomes problematic mainly when it stops being one option among others and turns into a prolonged constraint.