Ridiculous recovery time - 52 hours recuperation

Today I ran 14 kilometers at 133 heartbeats, at the end the clock gave me 22 hours of recovery. Then my coach told me to do 4 straight stretches of 100 meters in 18 seconds. After that, setting the clock gave me 54 hours of recovery for a 5-minute session of which I only ran 400 meters and the rest was rest. Why does this happen?