....when training for a contest that involves anywhere between one and twleve, 3-minute rounds' intensity?
One reason is because that type of long distance running slims you down and most boxers have to fit into a weightclass. Running long distance improves your overall stamina, improves blood circulation, and stresses the whole body. Keep in mind they might also be doing a jog/run, jog/run, windsprint-type of running that allows them to switch it up and improve acceleration. There are a number of reasons, but it depends on the boxer and what they are trying to accomplish with their training. Many boxers balloon up between fights, and long distance running slims you down fairly quickly.
Okay, but why not do sprints for 3 minutes, followed by 1 minute slow-jog....10 times? :dunno: Same as Ali used to do with hitting the heavy bag, rope-jumping etc
Most trainers I have had would get us to do both. One trains base stamina, core strength and helps cuts weight. The other is interval training. MTF :dunno: