Pressure, tendinopathy, and movement

I recently went down a rabbit hole, like I sometimes do, about tendinopathy. Tendinopathy is a poorly understood cause of pain attributed to overuse. It happens at the tendon, the structure that connects muscle to bone.

Pain is weird. It’s multi-faceted and difficult to pinpoint. We can sometimes feel when the injury happens, but why it happens at that moment in time can remain something of a mystery. The runner who steps funny and feels a zing in her calf. The pole dancer who moves into a splits position they’ve done a thousand times and feels a pull in the hamstring insertion. The hobby exerciser who pulls himself up into a pull-up position, an exercise he has done every Monday and Friday for the last ten years only to feel a strange twinge in the elbow.

Why suddenly in that moment of time did pain rear its head? Repeated exposure to an activity is, after all, supposed to make you stronger. So why did the tissue suddenly decide, “nope. Not today”?

Researchers like to speculate about the why because the person who solves pain not only helps people, they make lots of money. This speculation by researchers seeps out into the general narrative that is espoused be all kinds of professionals. And so, we learn things like our posture caused our pain, the way we do a specific thing caused our pain, our tight muscle or weak muscle caused our pain, or the way we are sleeping caused our pain. These are the reasons the injury occurred and they are the reason the tissue isn’t healing and the pain is still there, weeks or months after the initial injury.

It’s important to note that someone else with a similar activity history may never experience tendinopathy. Is that sheer luck? Or, perhaps, it’s the equivalent of the genetic lottery that causes two people participating in the same movement hobby to have very differing levels of pain and injury that impacts the activity.

Or, perhaps, it’s a matter of paying attention, of noticing when something feels funny and re-routing, taking a rest day, moving less, or performing a similar—but different—movement.

The reality is it is impossible to actually know why pain like tendinopathy happens. And maybe that isn’t the part that’s important. Maybe the part that’s important is how you work with the injury and continue to move.

Since my job is keeping people moving, this is also the part that’s interesting to me.

My interest was sparked, in part, by a paper I read recently on the topic. The authors state early that *the tendon cell regulates the extracellular matrix and pathology (i.e., injury), occurs when there is a failed adaptation to a disturbance of tissue homeostasis .

More simply, tendon cells regulate the three-dimensional network that creates structure and support to neighboring cells. When the tissue (and the three-dimensional network) are thrown out of balance and no adaptation takes place to regulate the change that has happened, injury may occur.

And what might be one of the more important factors for tissue homeostasis?

This is where things got really interesting. Tissue pressure homeostasis, the authors suggest, may play a role in tissue resilience.

The thing about pressure…

Pressure is how the brain determines how to move. Specialized cells in the skin detect vibration, pressure, touch, and cutaneous tension. Specialized cells in ligaments, muscles, tendons, and joint capsular tissues detect pressure within the body, such as compression, rotation, stretch, and joint position. This pressure is all input that the central nervous system (the brain and spinal cord) uses to determine what happens next; what happens next is always a movement of some kind.

Imagine you are sitting on your right foot. You sit on your right foot for a while, until your brain begins sending you signals that you need to move your foot. This sensation of the foot “falling asleep” is interpreted as discomfort by you. The compression on the foot created pressure on the cells within the joint. That information was sent back up to the brain, causing you to shift positions.

Altering pressure alters the experience of your body and the movement that follows. If pressure is applied to the skin, joints, and musculoskeletal system in a way that disrupts pressure in tissues, this might be problematic.

So how do you maximize input? We will discuss that next when we talk about why surfaces matter.