When partially paralyzed people for purely neurological reasons try to move their paralyzed limbs (during rehabilitation or whatever) they struggle very much and are exhausted afterwards. Why is that when their muscles (seems the reason for exhaustion) are absolutely fine?
IME pain. Extreme pain, whatever the cause, is exhausting.
The effort of trying to move a limb that you cannot move is also debilitating - if you tried to lift a heavy object, that was too heavy to lift, you’d be worn out from the effort.
Muscles need nerves to move. If a limb is paralyzed there’s no effort involved trying to move it because there aren’t any nerve signals getting to the muscles.
If a limb is partially paralyzed only the innervated muscles work. Whatever muscles are paralyzed are lost strength in that limb, so the functioning muscles have to work that much harder. The paralyzed muscles can also suffer spasms or contractures which can work against the functioning muscles.
I wonder if this isn’t also related to what I’ve seen when I try using my computer mouse with my left hand. I’ve experimented using my left hand because it relieves back pain, but it’s amazing how quickly that hand gets tired. It’s not that using a mouse is a lot of physical exertion; it’s that I’m having to work double-time in controlling movements that I’m just not used to. Instead of fluid, graceful movements, I’m tense and jerky because I don’t have the coordination in my left hand. After a couple of days mousing left-handed, I have more control with less effort and the fatigue drops off.
I am not paralyzed but I do get sleep paralysis sometimes. That is when you wake up and you literally cannot move anything except maybe a fingertip for a couple of minutes until you fight your way out of it. It is exhausting to try to move when you are in the paralyzed state. The reason is that you are trying as hard as you can to do something that you literally can’t. You subconsciously tense up other muscles especially those used for breathing and wear yourself out as you struggle to do something that the rest of your body won’t cooperate with.
The sensation of exhaustion can be emotionally based. A person giving evidence that is hotly contested over a few hours is just sitting there, but when they leave the court room, they will feel thoroughly knackered.
You can try this yourself if you are a good enough actor. Place your hands on a table completely still. Now pretend you are paralyzed and your hands won’t respond to the regular signals from your brain to get them to move. Try to will them to move as hard as you can for 5 minutes to come up with an alternate strategy. If you are doing it right, they will not move at all but you will be very tired and frustrated about 2 minutes in. Paralyzed people are always exhausting themselves with the faint hope that they can come up with a way to make their non-responsive parts respond and that is exhausting by itself aside from any other physical complications.
No, that’s pure projection on your part and not how it works. Do you think if you were missing an arm you’d still try to pick things up with it in the faint hope it would re-appear?
Probably. 60% - 80% of such people get phantom limb syndrome.
Like I said, I get sleep paralysis which very a very real and terrifying albeit temporary form of paralysis. My description of the problem is exactly what it feels like.
[tangential side-track]
For many years in my younger days I had sleep paralysis incidents quite often. (They seem to have mostly gone away, though.) In my brain-addled state during those episodes, it was terrifying for a long time – I thought if I didn’t somehow fight it off I would be permanently paralyzed.
There was another symptom that I have NEVER seen mentioned in any descriptions of sleep paralysis: Immediately after the episode ended, I would be awake, and with a feeling of profound bodily relaxation. (ETA: Actually, after an episode I felt extremely relaxed both physically and mentally.) I just felt totally limp and relaxed afterward. This sensation was actually quite nice, and persisted for some 18 hours or so – that is, well into the following day.
Once I finally learned that these episodes were harmless and not to be feared, I actually began to look forward them.
[/tangential side-track]