system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what exactly is the science behind a 'second wind'?
gpt
in the first portion of the exercise bout the "second wind" refers to your bodies switching from a majority of Anaerobic energy systems to primarily aerobic energy systems. when you first start running your body doesn't really know how long this shindig will last so it pulls out all the stops on providing oxygen and ATP to your working muscles (anaerobic) but after about 15 (energy plateau) mins or so it gets the idea that this isn't going to be a sprint and begins to switch from the more powerful anaerobic systems to utilizing the aerobic energy systems that are more efficient.