Why do our muscles get sore after exercise?

Our muscles get sore after exercise because they work really hard and need time to rest.

When you run, jump, or lift something heavy, your muscles are like little engines that go vroom-vroom. They use tiny parts called fibers to move your body. But when those fibers work really hard, some of them get a bit broken, kind of like how a toy car might break if you push it too fast.

When the muscle fibers are broken, they send out little messages that make the muscles feel tired and achy. This is why your legs or arms feel sore after playing sports or doing lots of jumping jacks, because the muscles had to work extra hard, and now they're telling you, "Hey, I need a break!"

It’s like when you ride your bike really fast for a long time, by the end, your legs feel like they’re made of noodles. But after some rest, they’ll be ready to go again!