Why Do We Get ‘Sore’ When We Exercise a Lot?

When we exercise a lot, our muscles get really tired. They work so hard that they start to feel sore, like after you’ve been running for a long time or lifting heavy things. It's kind of like when your legs hurt after jumping on the trampoline all day.

When we move our muscles, tiny fibers inside them get stretched and broken. This makes our body send special messengers to help repair them, and that’s what causes soreness, it feels like a little ouch in your muscle.