system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What physically happens to your body when you get a second wind?
gpt
IIRC it's a combination of your body switching off non-essential functions such as digestive processes to redirect that energy to the muscle groups you are using and a blast of natural drugs released into your blood stream in order to facilitate your ability to 'escape' whatever it is you're running from.

Mostly the drugs/chemicals though.