Connecting the Dots: Understanding Tensegrity & Mechanotransduction

As healthcare practitioners we all understand how movement of our bodies is as important for human health as eating right, sleeping, and well everything else!  We understand that through rehab we guide the way injured tissues heal - but what we might not understand is how does this process occur?  Is it even important for ourselves and patients to know?  Too often we find ourselves limited (or are limited by surgeons/doctors/protocols) in this process as to make sure we do not over-stress the healing tissue and by avoiding certain motions in rehab.  Unfortunately there are times when that thought process continues throughout the rest of the patients life.  As an example, I am sure we have all had a patient that comes to therapy with a current or past injury and states “I was told never to squat, raise my arm over my head, run, bend my back, etc.”  Is this the appropriate thinking?  How can it be?  It never seemed to make sense to have healthcare and movement professionals out there and tell patients to simply avoid the things that are hurting them.  How can we expect tissues to be resistant to future injury if we never load them the correct way?  The answer may lie in the principles of tensegrity and mechanotransduction.  

All cells in our bodies sense mechanical forces and convert them into changes in biochemistry and gene expression – a process called “mechanotransduction”.  This was first coined back in 1890 - and was literally defined as “the employment of mechanical forces for the curing of disease.”  However in schools and PT programs around the country I am not sure how much this concept is properly emphasized.  In reflecting in my past experiences and speaking with other healthcare professionals it seemed all too common that our internships would provide the on the job training we needed - but what if you were at an internship that only utilized modalities/rest and activity avoidance principles to get patients to feel better?  Well you would be in trouble!

The work of mechanotransduction has further revealed that molecules, cells, tissues, organs, and our entire bodies use “tensegrity” architecture to mechanically stabilize their shape, and to seamlessly integrate structure and function at all size scales.  Or put more simply our bodies resemble the toy below: Everything is connected to everything.

This “toy” probably looks familiar.  Who knew that when we were infants we were holding the key to human biology in our hands!  

The musculoskeletal system, which is comprised of an interconnected network of connective tissue is a framework that supports the weight of our bodies, allows us to rapidly adjust to resist external forces, and permits us to move freely in our environment.  As Tom Myer’s states we should think of human anatomy not as "600 muscles in one pocket, but rather one muscle in 600 pockets."  Our bodies stabilize joint regions, by imposing an internal tension or “prestress” to reduce the excess play in the system and prevent injury.  Doing so however allows that movement of one element is felt by all others - the concept of everything is literally connected to everything via binding of specific cell surface receptors, known as “integrins.”  Put more simply: tug on the lower part of your shirt - you should feeling pulling on your shoulders as the cotton (or whatever material your wearing) stretches and shares load throughout the entire shirt.  Now if we compare to our body, the loads and stresses placed in the system channel through similar elements, which produce physical distortion of the living tissues that comprise these organs.  For this reason, integrins have been shown in a wide variety of tissues to act as mechanoreceptors – they are among the first molecules on the cell surface to sense a mechanical signal, and they transmit it across the cell surface via a specific molecular pathway.  This provides stimulus for our brains and helps us interact with the environment around us.

In summary, every time we move our arms/legs/etc, the muscles contract, the bones compress, and the skin slides/glides without any irreversible injury (Normally).  This is made possible because most of the networks that comprise living tissues rearrange in response to stress, and then return to their original position when it is released, as is observed in all tensegrities (like the toy) - unless it is “trained” to do otherwise!  This is one of the reasons that manual therapy is only “temporary”.  We can mold/release/press/release a tissue, promote adaptation (for a few minutes) before the tissue returns to its previous state.  Have you ever had a patient that felt “great” after their session only to say there pain came back 15 minutes after they left?  Our manual therapy inputs open a window - if we can maintain stresses and communicate to the injured area, then and only then do our bodies truly remodel themselves through “mechanochemistry”.  A perfect example is an ACL reconstruction.  What starts out as a graft of patella, hamstring or cadaver tissue literally remolds and becomes a ligament based on the stresses and forces placed through the tissue.  This holds true for any healing tissue.  Ever wonder why people chronically sprain their ankles?  Aside from poor neuromuscular control at their hips they likely have never trained their lateral line/ankle to accept and bear load because what is the one motion themselves and their brains avoid?  Inversion!  Which is a rather important motion for the common ankle sprain and overall healthy function of the ankle.  

Are these principles you were/are familiar with?  Whether or not you were well versed in them, do you think patient education or understanding of these processes can assist rehab?

Until next time, Happy Rehabbing!