Why do you only feel muscle soreness the morning after?

Hi Craig,

I don't think anyone knows why it takes 24+ hours to really feel DOMS and I don't think that there's any definitive research that explains why either (Lauren may know more on this though).

I do know that it takes longer to set in as you get older though (unfortunately), which probably means slower recovery.

You may heel more during sleep (although I don't think that's actually been proven either) but muscle repair occurs throughout the day if the process is stimulated by resistance training.

You may hurt most first thing in the morning due to stiffness from not having moved throughout the night, the same happens if you sit down for a long time when you have DOMS...the first few steps are a killer the day after a big squat session!

I think the natural inflammatory process that occurs with resistance training takes a little time to occur in order for you feel the pain part of the inflammation. Remember that the resistance training is creating micro-tears in the muscle tissue.

Hi Gentlemen!

Craig, thanks for another fantastic question! I apologize for my delay in responding. Unfortunately I’ve been spending 6+ days/week caught up in a big project here at the hospital and am finally now able to leave in the evenings before dark and feel like I’m rejoining the rest of society!

Our muscles are made up of lots and lots of fibers, just like a piece of cloth is. We know that eccentric exercise, like running downhill, is more likely to cause DOMS than other types of exercise. So let’s say we take a piece of fabric, and stretch it, REALLY stretch it out, let kids play tug of war with it, over, and over again. After all of that really intense stretching, the fabric loses its shape and some of the fibers might even be torn or ripped. This is, in a nutshell what’s happening to your muscles after an intense bout of eccentric exercise, and what starts the process that result in DOMS. As the muscles become damaged, calcium is released by the tissue, and this tells the body that the muscle needs to be repaired.

The repairing process is where inflammation comes into the discussion. It is important to keep in mind that this is the same healing process that occurs when you injure yourself in other ways (like when I stub my toe). So first in order to repair the muscle, all of the damaged muscle needs to be cleared out. The body sends two types of white blood cells, called monocytes and macrophages to the damaged muscle to help break it down. Inflammation also produces substances that make the pain receptors in the muscle more sensitive; I assume to protect us from re-injuring ourselves before the repair process is complete. In addition, swelling (edema) accompanies the inflammation.

So yes, our bodies take the time while we’re sleeping to repair themselves, but unfortunately, the body’s way of healing overstretched muscle from a bout of unaccustomed eccentric exercise includes all of the pain that is associated with DOMS.
I hope this helped answer your question! Thanks for your patience with my reply!

So from the point at which we finish an exercise session to when we go to sleep, the damaged muscle tissue is being removed from the muscle, and then when we're asleep the repair process starts and produces inflammation to stop us doing more damage in the morning when we get up and start moving again? Makes sense to me! Thanks Lauren!

Hi Craig,

I'm not exactly sure of the timeline of events, but the entire repair process is going on until your symptoms go away; so it takes a day or two from soup to nuts. I'm glad this was helpful!

Hi Craig,

There isn't some sudden shift from removal of damaged tissue when we're awake to repair the second we nod off. This occurs during the whole duration of the healing process.

There probably are phases due to hormonal fluctuations, etc...for instance, testosterone levels are highest in the morning, so perhaps even more repair occurs then than during sleep?? Then again growth hormone increases during sleep, so maybe more tendon/ligament repair occurs at that time (as GH is particularly good at building and repairing certain joint tissues)?

Hmmm, the main thing that I was wondering is why you don't actually feel the soreness until the next day? I suppose like you said Mark, it could be simply because we haven't moved for 8 hours. Thanks guys.