system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What causes you to vomit when you overexert yourself with exercise?
gpt
Your body equates this exertion as a sign of "flight" in the fight or flight response and thus what's to empty its contents. Plus the blood flow is diverted from the abdomen and to the extremities, which causes the gastric sphincters to relax, making it easy to vomit.