What does it mean: When you’re muscles are sore it doesn’t necessarily mean you’re out of shape or that you’re weak. Even the biggest body builders or most fit triathlon runners experience muscle soreness. To experience muscle growth and strength you have to break apart muscle fibers and rebuild them, this is what causes muscle soreness.
When does it happen: When you tear apart muscle fibers with heavy weight or doing exercises your body isn’t accustomed to, your muscles literally tear a part and rebuild to be more efficient at performing those exercises the next time.
How long does it last: Muscle soreness can occur immediately after an exercise and last 2-3 days. Typically you will feel the most sore the day after performing an exercise your body isn’t accustomed to.
What can you do:
*I try and keep the science as simplistic as possible. If you want further details I can provide more information straight from the resources I have access to.