The Fascial Critics Have a Point. They're Also Missing It.

The claim that a therapist's hands can "release" or physically reshape dense collagen fibres is not well supported. Collagen is strong enough to suspend a car. Applying pressure to it through the skin is not going to reorganise its architecture. If that were the proposed mechanism, the sceptics would be right to dismiss it. The problem is that it is not the mechanism — and conflating the name of the treatment with a claim about collagen may be the single largest source of confusion in this debate. This post is an attempt to untangle it.

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The Criticism Worth Taking Seriously

The most cogent version of the sceptical argument goes roughly like this: fascia is a structural tissue, primarily composed of collagen. Collagen is not meaningfully deformable by manual pressure. Therefore, any claim that a therapist is "manipulating fascia" — in the sense of physically altering its structure — is implausible. The research on foam rolling, stretching, and myofascial release as mechanisms of structural change in collagen is thin, and what exists does not hold up particularly well under scrutiny.

This is a fair criticism of a particular version of the theory. And it is the version that, unfortunately, gets repeated in a lot of practitioner training material and marketing language — including, historically, some of our own.

Where the critique sometimes goes wrong is in taking the weakest version of the argument and using it to dismiss the entire field. The question is not whether a therapist can reshape collagen fibres. The answer to that is almost certainly no. The more useful question is: what is actually changing after manual therapy to this tissue, and is there a plausible mechanism that explains it?

The evidence suggests there is — and it has nothing to do with collagen.

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The Tissue That Actually Changes: The Extracellular Matrix

Fascia is not just collagen. It is a composite tissue — and the component that appears most relevant to both the pathology and the treatment response is not the collagen itself, but the matrix in which the collagen fibres are suspended: the extracellular matrix (ECM).

The ECM of fascial tissue is rich in hyaluronan (HA) — a large-chain polysaccharide that, in healthy tissue, exists in a low-viscosity, watery state that allows adjacent fascial layers to glide freely over one another. [1] This free gliding is not trivial: Guimberteau's in-vivo endoscopic studies of living connective tissue demonstrated that the microvacuolar architecture of the ECM is in constant, dynamic motion during movement — a complex, continuously adapting sliding system that serves both mechanical and sensory functions. [2]

The pathological state — what practitioners using the Stecco Fascial Manipulation model call "densification" — is a change in the physicochemical state of this HA-rich matrix. Pavan and colleagues were among the first to carefully distinguish densification from fibrosis: the two are categorically different. [1] Fibrosis involves actual structural changes to collagen — scar tissue, adhesions, irreversible remodelling. Densification is not this. It is a shift in the viscosity of the hyaluronan within the ECM — from a free-flowing, lubricating state to a more gel-like, aggregated state that impedes gliding between fascial layers. Critically, this process is reversible. It is a biochemical state change, not a structural one.

This distinction matters enormously for the debate. When critics argue that fascia cannot be physically restructured through manual pressure, they are correct — and they are also, in the context of densification, arguing against a straw man. Nobody is restructuring collagen. The tissue that is changing is the HA-rich ECM between fascial layers, and the mechanism is a shift in its physical state.

The cellular machinery for this is now documented. In 2018, Stecco and colleagues described a previously uncharacterised cell type — fasciacytes — found specifically in the loose connective tissue between fascial layers. [3] These cells are specialised for HA synthesis and regulation. They are the cells that maintain the homeostatic, low-viscosity state of the interfascial matrix. When subjected to mechanical loading abnormalities — either chronic underloading (immobility, sedentary posture) or chronic overloading — the HA environment shifts toward the high-viscosity, aggregated state that impairs fascial gliding. [4]

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How the Mechanism Actually Works

If collagen isn't changing, what does a manual therapy session do?

The current evidence points to a thermal and mechanical mechanism acting on the ECM. Deep friction applied to fascial tissue elevates local temperature in the treated area. Pratt and colleagues, reviewing the biology of HA at the fascial interface, documented that temperatures above approximately 40°C disrupt the superstructure of aggregated HA — triggering the gel-to-sol transition that returns the ECM to its low-viscosity, gliding-permissive state. [4] This is not a structural change to collagen. It is a physical chemistry change in the ground substance.

Stecco and colleagues described what happens after this in a 2023 review: mechanical stress during treatment depolymerises high-molecular-weight HA into lower-molecular-weight fragments. This initiates a controlled inflammatory cascade — activation of TLR-4 and CD44 receptors, release of TNF-α and IL-1β — that peaks around 12 hours post-treatment and self-resolves within 24–48 hours. [5] This cascade is not a side effect. It is the mechanism of HA remodelling. It also explains post-treatment soreness — and it explains why non-steroidal anti-inflammatory drugs should not be taken in the window following fascial treatment, as they suppress the very process that drives the improvement.

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The Molecular Machinery: The CHA Axis and Its Downstream Consequences

The gel-to-sol transition described above does not simply happen because heat was applied. A 2025 review by Kirkness and Scarlata synthesised evidence from fasciacyte and mesenchymal cell research to propose what they call the Ca²⁺–HA (CHA) axis as a unified mechanotransduction framework for the process. [8]

When mechanical force is applied to fascial tissue, mechanosensitive ion channels at the fasciacyte membrane — Piezo1, TRPV4, and P2Y2 receptors — respond to deformation with a calcium (Ca²⁺) influx. This activates a downstream signalling cascade — CaMKII, PKC, MAPK, CREB — that drives expression of HAS2, the enzyme responsible for HA synthesis. New HA synthesis peaks four to six hours after the mechanical stimulus. The molecular weight of the newly synthesised HA then determines the biological outcome: high-molecular-weight HA binds CD44 receptors to restore homeostasis and downregulate mechanosensitivity (a “Quiet” state); low-molecular-weight HA fragments bind RHAMM receptors, amplifying pro-remodelling and pro-inflammatory signalling (a “Riot” state). Kirkness and Scarlata describe this CD44/RHAMM oscillation as the fundamental regulatory switch of ECM homeostasis. [8]

This framework places the post-treatment inflammatory cascade — described by Stecco and colleagues [5] — in its proper molecular context: not a side effect, but the activation of a tightly regulated circuit. When manual therapy fragments self-aggregated HA, LMW fragments activate the Riot pathway to initiate clearance; recovery completes when new HMW-HA synthesis re-engages the Quiet pathway via CD44. Excessive or chronic mechanical stress — sustained altered loading, prolonged immobility, or repetitive overuse — may progressively overload this system, shifting the balance toward sustained pro-remodelling activity and, over time, toward the structural changes that represent the far end of the fascial spectrum.

The downstream consequences of sustained imbalance in this system are mapped by two further bodies of research. Pirri and colleagues (2025), in a narrative review of fascia’s role in complex regional pain syndrome, traced the cytokine cascade: persistent elevation of IL-1, IL-6, and TNF-α drives fibroblast activation, excess collagen deposition, and ultimately structural fibrosis that both restricts mobility and generates mechanical pain. [9] The thoracolumbar fascia — with a nociceptive fibre density of 9.01% of cross-sectional area, the highest of any fascia studied — is particularly capable of sustaining the peripheral and central sensitisation that can follow this fibrotic change. The mechanism is not limited to CRPS; the same cytokine-driven cascade operates across the severity spectrum of fascial dysfunction, CRPS being an extreme expression of processes that are active at far lower intensities.

Kodama and colleagues (2023) document the specific cellular transition through which mechanical stress converts fascial fibroblasts into myofibroblasts — the cell type that maintains chronic fascial tension independent of any neural drive. [10] Under repeated or sustained mechanical stress, fibroblasts progress through a proto-myofibroblast intermediate state (actin stress fibres) to full myofibroblasts that form fibronectin bridges and generate ongoing contractile force via TGF-β1. Two variables that modify the likelihood of this transition are clinically relevant: ageing, associated with progressive lumbar fascial thickening (+40 to 77% in older cohorts compared with younger adults); and estrogen, where receptor β (Erβ) activity normally inhibits TGF-β expression and fibroblast-to-myofibroblast conversion, making prolonged estrogen deficiency a potential biological accelerant of fibrotic progression in the posterior fascial chain.

The picture that emerges is mechanistically coherent: manual therapy at a densified fascial site activates the CHA axis, triggering controlled HA fragmentation (Riot state), initiating the inflammatory cascade, and enabling fasciacyte-mediated restoration of normal HMW-HA (Quiet state). When this process is not initiated — or when mechanical load continues to drive the system beyond the adaptive range — the cellular biology favours a progressive shift toward structural change. This is the argument the sceptics have not engaged with, because it is not the argument they are critiquing.

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What the MRI Evidence Shows

In 2020, Menon and colleagues at NYU School of Medicine published a small but landmark study that, for the first time, used T1ρ MRI mapping to directly visualise ECM changes before and after Fascial Manipulation in patients with chronic elbow pain. [6]

T1ρ MRI quantifies the concentration of bound versus unbound water in tissue — a proxy for glycosaminoglycan (GAG) content, which is the molecular family to which hyaluronan belongs. After three sessions of Fascial Manipulation, there were statistically significant changes in bound and unbound water concentration within the deep fascia at the treated sites. The tissue was measurably different on MRI. The researchers described this as consistent with a reduction in the densification state of the fascial tissue — precisely what the model predicts.

What did not change? The collagen architecture. The imaging modality used does not capture collagen fibre reorganisation, and the treatment duration used would not be expected to produce it. The critics who argue that collagen is not being restructured are right. The MRI shows that something else is — and what it shows is entirely consistent with the HA viscosity model. We explored this in more detail in our earlier post on the MRI evidence.

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Why the Sensory System Is the Bridge

The clinical question — why does changing the HA state of the ECM produce changes in pain and movement? — has an anatomically grounded answer.

Fascia is not an inert structural material. The deep fascia is richly innervated, with a documented mechanoreceptive and nociceptive function. [7] Ruffini endings, Pacinian corpuscles, Golgi tendon organ-like endings, free nerve endings including type C (pain-sensitive) fibres — all of these are embedded within and around the fascial tissue. Muscle spindles and Golgi tendon organs — the primary proprioceptive sensors that regulate muscle tone and movement — are encased in connective tissue that is continuous with the fascial system.

When the ECM in which these receptors are embedded shifts from a free-gliding, low-viscosity state to a stiff, high-viscosity state, their mechanical environment changes. The loading threshold at which they fire, the relationship between tissue displacement and receptor deformation, the background level of afferent input from the region — all of these are altered by the state of the surrounding matrix. A Ruffini ending embedded in densified HA is mechanically different from the same receptor in a fluid, low-viscosity matrix. Its firing characteristics change. And because these receptors contribute to both proprioception and central pain processing, the downstream clinical consequences — altered movement quality, changed pain thresholds, modified motor output — follow logically.

This is why the treatment effect is both immediate (the gel-to-sol transition is rapid under appropriate mechanical and thermal input) and further consolidated over 24–48 hours as the HA remodelling cascade completes. [5]

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The Naming Problem

None of this means "fascial manipulation" is a perfect name for what is happening. As a descriptor, it implies that fascia — the tissue — is being manipulated in the structural sense. A more mechanistically accurate name might be "extracellular matrix manipulation" or "interfascial hyaluronan treatment." But these terms would create immediate barriers: clinical confusion, patient incomprehension, and the abandonment of a decade of research literature organised under the current terminology.

The name is conventional. The mechanism is not mysterious. And the evidence increasingly supports the target — the ECM, not the collagen — as a legitimate and distinct clinical objective.

The appropriate response to the valid scepticism about collagen restructuring is not to abandon the fascial model. It is to be precise about what the model actually claims. The critics have correctly identified the weakest version of the argument. What they have not always engaged with is the stronger version — the HA viscosity model, the fasciacyte biology, the MRI evidence, and the sensory receptor physiology that links ECM state to clinical outcomes.

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What This Means for You

If you have seen criticism of "fascial therapy" online and are wondering whether we are practising something with a thin evidence base — the criticism has a legitimate target. Unsubstantiated claims about "releasing" structural fascial adhesions through surface pressure are not well supported. That is not our model, and it is not what the evidence describes.

If you have had treatment elsewhere described as "myofascial release" and are not sure whether it is the same as what we do — there is meaningful variation within the broader field. The specific approach used here, Fascial Manipulation by Stecco, is grounded in a model centred on HA viscosity and ECM state — supported by histological, biochemical, imaging, and clinical evidence. The treatment protocol is systematic and reproducible, not intuitive.

If you want to read the primary evidence, the papers cited in this article are indexed in our research library and cited in full below. The Menon 2020 MRI paper [6] and the Stecco 2023 HA cascade review [5] are both open-access. They are not light reading — but they are substantive.

The bottom line: the name may be imprecise. The mechanism is increasingly well-characterised. The tissue that changes is the extracellular matrix — specifically the hyaluronan within the loose connective tissue between fascial layers. The receptors whose behaviour changes as a result are the mechanoreceptors and nociceptors embedded in that matrix. The clinical changes that follow are a predictable consequence of restoring the mechanical environment in which those receptors operate.

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Please note: This post is intended for educational purposes only and does not constitute clinical advice. Individual presentations vary significantly. Please consult a registered health practitioner for advice about your specific condition.