system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 why is exercise supposed to make you tired if atp is not stored?

I read that atp is produced constantly as needed and that you can only store about a minutes worth, so how is exercise supposed to make you tired and sleepy if you're not using up your energy?
gpt
You are using energy. Atp and glucose. A good analogy I've heard is atp is like a quarter. Good for small amounts of energy. Like using a parking meter or doing laundry. Glucose is like a 10$ bill. It's easier to transport around than 10$ in quarters, but doesn't work for paying the meter. During large exercise. You are spending lots of money, and your body needs to recover that, hence you being tired.