Tuesday, April 10, 2018

Into everyone's life a bit of knee pain may fall

I have just returned from teaching a class in Barcelona.
Lovely city.
Glad I finally had an opportunity to see a bit of it, namely the Gaudi architecture.

In Europe, the bathroom stalls are like small rooms. They are floor to ceiling, with doors that close completely - no gaps.
They also often have a small step up.

So, the first day at the teaching venue I went to visit the ladies' room.
I blame jet lag. I blame the fact it was the first teaching event of the season and I was adrenalinized.
I blame myself for forgetting there was that small step.

On the way out of the stall my brain made a stupid motor prediction error.  The floor was about 3 or 4 inches lower than I expected. My brain did not account for the step. The floor wasn't where it was supposed to be. My foot hit the actual floor and jarred my whole body. 

From then on the knee was very crabby with me. 

It's getting better now, 5 days later, and it felt fine the day of the incident, but the next day, it refused to climb or descend stairs smoothly, and after I had sat awhile, getting up and asking it to move felt quite painful. Medial knee, saphenous nerve, of course... 
I taped it, which helped me feel it much less so I could focus on the people and not on myself.

In younger years there would not have been pain associated with a dumb move like that; I know because I've made dumb moves like that in the past, and they didn't used to bother me. I wonder if, when we get past 60, 65, if the immune system doesn't get grumpier and stronger? Quicker to throw mast cells at anything? For any excuse?

Or the whole spinal cord? Maybe as the brain starts to falter, the spinal cord seizes the opportunity to do what it tries so hard to do against all that built-in descending inhibition, which is to be an amplification system for nociceptive input. 

I have this fantasy that the spinal cord sits in there, resentful and fuming that the brain grew big out of one end of the brainstem while it, the spinal cord, stayed the same. 

That it struggles all its life to take precedence again, as it still does in fish, and be The Main Event, the star of the central nervous system.

I fantasize that it plots a takeover, or more accurately a takeback, gradually erodes the system, makes small gains, and eventually (in aging mammals, primates, humans) succeeds to a certain extent. That it does this by making nociception much bigger and more dramatic than need be and the spinal cord glia stronger/more facilitated, which go on to sensitize the sensory branches of a peripheral nerve, whichever one received the most mechanical force during some predictive coding mishap.
Positive feedback loop.
Spinal cords, doing their protective thing but at the same time hastening physical entropy! 

Maybe the reason for doing deliberate daily exercise/movement/strengthening is simply to activate all large fibre sensory input from muscle, in order to keep spinal cord function locked safely in its cage. (See Foster et al 2015, my favourite paper so far about stimulating glycinergic interneurons in the spinal cord that inhibit nociceptive input at the first synapse in the dorsal horn.)

This is me, age 67, pondering and probably trying to talk myself into exercising more regularly again.
I have always said aging is not for sissies. 


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