While stiffness can come from joints or muscles, research shows that fascia often plays a major role—especially when the restriction feels vague, widespread, or nothing shows up on scans.

This page explores what current research is discovering about how and why fascia stiffens—from reversible changes like densification to more lasting ones like fibrosis—and how the nervous system plays a role in all of it.
Fascia isn’t one solid sheet—it’s made of layers that need to slide over one another, like overlapping socks or gloves. Between those layers is a slippery fluid rich in a substance called hyaluronan (or hyaluronic acid), which acts like a natural lubricant.
Densification: When the Tissues Feel Sticky
But sometimes, that lubricant gets thicker and stickier. Instead of sliding, the layers begin to drag or even stick together. This is called densification.

Densification doesn’t mean damage. The tissue isn’t torn or scarred—it’s just not moving as freely. You might not see it on a scan, but you can often feel it—like a tug, a dull tension, or stiffness that just doesn’t release.
Fibrosis: When the Tissue Changes Structure
While densification is about stickiness and reduced glide, fibrosis involves deeper, more lasting changes in the structure of the tissue.

Fibrosis can develop when the body lays down extra, rigid collagen—usually in response to ongoing strain, inflammation, or injury that hasn’t fully resolved. Instead of just sticky fluid between the layers, the tissue itself becomes thicker, stiffer, and less adaptable—a bit like internal scar tissue.
This illustration shows how your body’s fascia is organized in layers—from the skin down to the muscles. Between the deeper layers is a thin zone of loose connective tissue that allows them to glide over each other. This layer contains hyaluronan (HA), a natural lubricant that helps fascia stay smooth and responsive.
In healthy tissue, the thin layer between fascia layers is hydrated and slippery, helping them move freely. But when hyaluronan breaks down or becomes sticky, the layers start to catch and drag. This is called densification—and it can lead to stiffness, tension, and altered force transmission through the body.
The Nervous System & Fascial Tone
Fascia doesn’t just respond to movement—it also responds to stress, tension, and emotion. It’s deeply connected to the nervous system, especially the part that runs in the background: the autonomic nervous system (ANS).

When the body is under stress—whether physical, emotional, or postural—the ANS can become more active, especially the sympathetic system (sometimes called the fight-or-flight response). This can cause fascia to hold more tone or tension, even when there’s no injury.

Researchers like Robert Schleip have shown that fascia contains special cells called myofibroblasts—tiny contractile cells that can tighten the tissue from within, similar to smooth muscle. These cells help with healing by pulling tissue together after injury—but they also respond to the body’s stress state, becoming more active and tend to hold more contraction when the nervous system is on high alert
Fibroblasts are the cells in your fascia that help build and maintain the tissue, like caretakers of your body’s connective network. When needed—like after injury—they can transform into myofibroblasts, which pull tissue together to help it heal. But if they stay active too long, they can hold tension and contribute to long-term stiffness or scarring in the fascia.
If the body stays in a state of stress or guarding for too long, fascia may hold that tension—leading to a lasting sense of restriction. You might feel this after injury, during periods of stress, or even just from lack of rest or recovery.

Fibrotic tissue—such as in long-term low back pain—often shows increased myofibroblast activity. This type of tissue tends to be already under tension and may respond best to carefully dosed input rather than aggressive pressure.

The goal isn’t to force change—it’s to offer the right input, at the right time, so the tissue can begin to adapt.
What About Adhesions?
Adhesions are areas where tissues that should move independently—like fascia and muscle—become abnormally stuck together. They often form after surgery, inflammation, or trauma, and can limit motion more severely than densification alone. People often describe adhesions as areas that feel stuck, pull with certain movements, or don’t “let go” easily.

The following image shows an example. The top section shows healthy fascia and muscle with smooth, sliding layers. The bottom section shows how, after injury, the layers can become stuck or less defined—suggesting reduced glide and potential adhesions.
📚 Further Reading & Resources
Compiled by Joe Liguori