Your lymph system relies on the movements of your skeletal muscles to push anything not water soluble through your body. This includes fats, various local inflammation signaling molecules, etc.
When you feel sick don't stay in bed, go for walks, a large part of your immune system is passive and rely on muscle contraction to work optimally.
And a common reaction to being sick is shivering, so maybe the body is already compensating for the lack of movement.
Do you have a source for this? I haven't heard this before and genuinely want to learn more about it. A cursory Google search didn't find anything related to this
https://www.mdanderson.org/publications/focused-on-health/ex....
If you have a typical office job, you almost certainly don’t even have enough time in the day to overtrain.
But overtraining isn’t just getting over exerted and having to rest for a few days or even weeks. It’s a very gnarly condition that’s ridiculously hard to get to. Most of us would mentally tap out long before.
It’s a lot like the difference between needing a break and being burned out. Getting tired and needing a break is normal, being burnt out is a serious condition.
And if you had not done sport for a long time and suddenly get back to it, trying to "continue" where you left, that is when injuries happen.
If anything, I think our largest (modern) collective societal health problem is that we do wayyyy to much trying to avoid straining the heart. For how much of human history were we not working mostly sedentary? It has a cost. The body is meant to be worked. It loses strength and stamina when it isn't. I don't think the answer is to do even less. Besides, do you know how many involuntary naps I'd take if I was laying down all day?