system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the body keep demanding I take deep breaths after hard running?

Just had to bolt for the train and was wondering why after I had finished running my body wanted me to keep breathing at that rate instead of immediately calming down to normal breathing.
gpt
Your body is reoxygenating your blood. Imagine your blood is like a battery, when you run, you drain from that battery really quickly. After a while, it runs out (you feel 'puffed') and you consume oxygen as you breathe it. When you stop running, you replenish your battery (reoxygenate all your blood). When it's full, you feel normal again. 

Edit: Note about carbon dioxide: When you 'drain your battery' you are left with the nasty byproduct of carbon dioxide. That is the nature of aerobic respiration to produce CO2 as a byproduct. However this does not change the fact that your lungs (the 'charger') have limited capacity for gas exchange, which causes the effect OP observed.