system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how muscles get stronger.

Like the tittle says. I'm not really sure how 'hurting' them or using them alot helps :)

EDIT:Thanks everyone for answering!
gpt
Imagine a village that has a very valuable treasure in it and the villagers build a big wall around it to protect the treasure!  Well lets say someone comes along and tears down the wall to get to the treasure.  The villagers are really upset by this and after the wall is torn down they decide to build it back up even bigger than before to keep people out and away from their treasure!  After all, the wall didn't do a good enough job the first time so they need a bigger, better wall to hopefully make it work the next time!  Of course, the villagers need really great materials to make a really great wall but as long as they have those great materials they'll keep building the wall back a little bit bigger and better each time it gets torn down.  After all, they have to protect that treasure!

Now think of muscle growth that way except that the wall is your muscle, the tearing down is your weight training, the materials for the wall are your diet, and the villagers are your body.