Hi there! :D
After a runner finishes a race, he/she is most likely going to breathe quickly and deeply for a few minutes.
Why?
Well, the first reason is because their heart rate is still very high from that running. That causes them to breathe deeply and quickly. The second reason is to release an acid called lactic acid.
What is lactic acid?
Lactic acid is a substance that is produced in your muscle tissues after intense or really extreme exercise. If they don't get rid of that acid by breathing quickly and deeply then later on it will cause them to be sore.
Hope this helped!~