system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people throw up after high intensity and strenuous activity such as cardio?

I know that vomiting is a reaction by the body to rid of what it deems toxic or poisonous, but what is the body trying to rid of during an extreme run?
gpt
It's not really a reaction by the body to get rid of something toxic or poisonous.  During an extreme physical event such as running, your muscles need a huge supply of oxygen, and your body responds by decreasing blood flow to your stomach and intestines and other internal organs, and increasing the blood flow to your heart and muscles.  The decreased blood flow to your stomach means that it is not able to digest food as efficiently, so it may try to get rid of the food by vomiting.

This is why serious long-distance runners will try to keep their energy up with those energy gel packs that are easy to digest, because it's basically just carbohydrates.