why muscles get tired

Sinistral mentioned the function of sleep further up the thread, I quote:

“Sleep has been found to be essential in the process of synaptic pruning and rewiring your brain after a given set of experiences. You need sleep to function and process information over time.”

Well, I guess its true then :slight_smile:

(Yeah, I read that, that’s why I mentioned the function of sleep in the first place :P)

Anyway, if it is true, I disagree with it :stuck_out_tongue: You can’t really separate your mind from your body. Mind sends the signals that heal the body, so… For instance, one day I’m sick. I sleep at night. Next day I wake up not sick. Or, I go for a run. I go to sleep at night. I wake up, my legs are sore as well. But, I sleep again, and the next day my legs feel a lot better. etc.

It’s not because you slept that you became well… it’s because your leukocytes fought off the invading pathogen. As for being sore and then not sore, that’s you damaging cells in your leg, and your body repairing or regenerating them. All of this gets relayed to your brain, but if you tried to stay up for n hours to see if you’d still get better from the sickness, you’d probably be in a worse state as your body scrambles its resources to keep your overstressed neural networks from damaging itself and diverts attention away from fighting the pathogen.

So if you if you stay up all night, your body uses resources it would otherwise use on your body, on your brain.

You’re right that you don’t go into a stage of accelerated healing when you sleep. But you still lose healing if you don’t sleep. So sleep still is crucial to physical healing…

You’re both wrong .

The reason you feel like shit one day and not the next has to do with cells in your immune system releasing molecules like interferon gamma and IL-2. After sufficient time has passed, cells don’t need to secrete as much. You don’t get feel sick because of pathogens but because of your immune system and you don’t get better because your brain told your immune system to tone it down because the brain isn’t connected to the immune system. You have to keep in mind that when you sleep, you sleep 8-10 hours. A lot of things happen in 8-10 hours and your body metabolism doesn’t work the same way in terms of temperature control and other such factors.

I also refer you again to the concept of perception and the influence of sleep on perception of pain. Its not just pain, but also how easily you feel warm and cold and all kinds of other things.

In regards to soreness, your cells in your leg need to repair. This takes time because cells need to divide, proteins need to be made, cells will migrate in and out of the site of damage with different effects. Damaged cells send out signals that cause the immune system to be recruited at the site of injury and this causes swelling, heat, redness and pain.

Sleep is important for reasons other than the ones hypothesized here.