Annamaya Kosha ( Physical Body ) - Collagen

Nikita
Aug 5
6 min read

Why astronauts lose up-to 20% of bone-mass without gravity and how yin-yoga helps us to keep our bones strong.

The idea that our bones needs to be exercised at first seemed ridiculous to me, but stress is actually a reason why our bones are strong.

Another misconception about our bones is that they are made of lifeless material - like the school mannequin we saw. But this is actually an image of dead bone, stripped of vitality, a mere remainder of mineral salts. A good analogy would be the branch of an old tree: dry and easy to snap.But living bone is more like the branch of a young tree - it bends with resilience instead of breaking.

This is because a living bone consists of a mixture of materials - a dynamic matrix of collagen, which gives it flexibility, and mineral salts like calcium phosphate, which provide strength.

Again the word flexibility we need to understand in context - collagen is found throughout our body, and collagen in muscles make our muscles less flexible - because it less flexible when other muscle fibres.

But collagen in our bones it is actually what give our body necessary flexibility and resilience.

What is Collagen?

Collagen is the key protein that forms the foundation of our tendons, ligaments, fascia, and

even bones. Unlike most proteins that clump together, collagen forms long fibrous strands that can take the shape of sheets, mats, or rope-like cords. It’s what makes our teeth strong, our skin elastic, and when it breaks down, it’s what causes wrinkles. Even the word itself — from the Greek meaning “glue producer” — tells us its purpose: collagen holds us together.

Out of the 27 types of collagen in the body, Type I is the most relevant here. It’s found in bones, skin, tendons, ligaments, and also in scar tissue during healing. For years, it was even used by plastic surgeons to plump lips — a testament to its structural importance.

Production of collagen

Collagen is continually being laid down and absorbed by the body. Fibroblast produce collagen in our connective tissue, and osteblasts in our bones.

Osteblasts are laying down collagen fibers. But osteclasts do the opposite - osteoclasts reabsorb the collagen, cleaning up old bones by degrading the collagen and releasing its component into the bloodstream.

When our body builds bone, tendons, or fascia, it first creates a soft web of collagen fibers — like threads being woven into a net. Over time, these threads form tiny connections between each other, called cross-links, which make the tissue stronger.

If the rate of production faster than rate of absorption, more cross-links are formed. This makes the tissue strong and firm, but also less stretchy — like a tight rope.

But if opposite is true - this creates tissue that is more flexible, but also weaker — like a loose elastic band.

Once the collagen framework (called osteoid) is laid down by the bone-building cells (osteoblasts), the body begins the next important step: mineralization.

Think of osteoid as a soft scaffold — it has shape and structure, but it’s not strong yet. To turn it into solid bone, the body fills it with tiny crystals, mainly calcium phosphate, which harden the tissue.

This process is called mineralization, and it’s what gives bones their rigid strength.

Directional stress

Biological tissues and their collagen fiber orientation imaged by second-harmonic generation microscopy. (a) Transverse cut of a human cornea. (b) Skeletal muscle from zebrafish (myosin). (c) Adult mice-tail tendon. (d) Surface cartilage from a knee of a mature horse. (c) ResearchGate

The direction of stress placed on our tissues is essential for how collagen fibers grow and

adapt. When osteoblasts (in bone) or fibroblasts (in fascia and connective tissue) first lay down collagen, the fibers are arranged randomly, like threads tossed in every direction.

But when mechanical stress is applied — especially in a consistent direction — something fascinating happens:

The stressed fibers generate tiny electrical fields, a phenomenon known as piezoelectricity. These electrical fields act like signals to the body, saying:

“These fibers are doing important work — keep them!”

As a result:

Stressed collagen fibers are preserved.
Unstressed fibers are slowly reabsorbed by cells like osteoclasts (which break down bone).
Over time, the tissue becomes perfectly adapted to the directional forces it experiences.

This process is the body’s way of making sure energy and resources go where they’re actually needed.

Image at the right displays directional alignment of collagen fibers

What Happens Without Stress?

A striking example of this can be seen in astronauts on space station "Mir". Because they live in weightless environment - there is no any stress applied to their tissues. Nasa studies have shown that they can loose 1 - 2 % of their bone mass in one month, and some of them up-to 20% in 6 month ! Imagine how gravity is essential for us. Simply walking is an exercise for our bones. Yin Yoga is another way intelligent way to exercise our connective tissues.

Our Body Reimagined

This cycle of collagen creation and mineralization and absorption is ongoing throughout life.

Every part of our body - even our bones - is alive. Far from being rigid or static, our bones are in a constant state of renewal, adapting and rebuilding themselves in response to how we move, rest, and engage with the world.

Yin Yoga, by applying gentle, sustained stress to these collagen-rich tissues, may stimulate fibroblasts and osteablasts - the very cells that produce collagen - encouraging them to repair, regenerate, and reorganize the connective matrix. It helps us to create a solid foundation of the most deepest layers of our physical body.

In truth, living bone is vibrant, dynamic, and alive — full of cells, blood vessels, and a matrix that constantly renews itself.

Blood Vessels in Bone:

Bones are highly vascular (rich in blood supply).
This blood supply:
- Delivers oxygen and nutrients to bone cells (osteocytes).
- Removes waste products.
- Supports healing and remodeling.

Nerves in Bone:

Bones contain sensory nerve fibers, mainly running alongside the blood vessels.
These nerves:
- Detect pain
- Sense pressure and position

Bone-lining cells:

A type of bone cell that cover the surface of bone where no active bone formation (by osteoblasts) or bone resorption (by osteoclasts) is happening.

They’re like the caretakers of resting bone surfaces.

Origin:

Come from osteoblasts that have finished building bone and become inactive

Functions:

Protective layer
- Shields the bone surface from chemicals and unwanted resorption.
Regulate mineral exchange
- Act as a barrier that controls the movement of calcium and phosphate between the bone and the bloodstream.
Signal for remodeling
- Can reactivate and turn back into osteoblasts if new bone formation is needed.
Communication role
- Work with osteocytes (bone’s sensory cells) to help coordinate when and where remodeling should occur.

Yin Yoga Connection:

When you place gentle, sustained stress on bone through Yin Yoga, the mechanical signals sensed by osteocytes can trigger bone-lining cells to activate into osteoblasts, supporting collagen production and mineralization in those areas.

Aging Of Connective Tissues

When collagen fibers in our connective tissues are healthy, they tend to be long, straight,

and aligned along the direction of the predominant stress. In a tendon, for example, these fibers run in parallel lines, giving the tissue both strength and flexibility.

But with aging, injury, or chronic strain, these straight fibers can become tangled, bent, and shortened. This change draws the muscle and bone closer together, reducing the possible range of motion. Within these tangled fibers, tiny particles can become trapped - including metabolic waste from nearby cells or even environmental pollutants like smoke or pesticides.

When fibers are long and straight, there’s less chance for these particles to get stuck. But once trapped, they can remain in the body for years - sometimes indefinitely.

Practices like massage and yoga help free these trapped particles by moving, stretching, and compressing the body’s collagen network. This movement can lengthen fibers and loosen bonds, allowing debris to enter the blood or lymphatic systems for elimination.

It’s long been recognized in Eastern traditions that yoga is a detoxifying practice. Now we can understand why: yoga works like wringing out an old sponge - twisting, stretching, and releasing - to keep our tissues supple, clean, and resilient.