I was recently reminded, quite painfully in fact, about why running the 5k is an important distance or event for triathletes to spend time focusing on. My reminder came in the form of a duathlon, which was a 5k run/30k bike/5k run. The pace from the start was fast. About 2 minutes into the first 5k of the du, I looked down at my Garmin and saw a 5:19 m/m average pace. The rest of the first leg is a blur to me. Once I regained conscious thought during the bike leg, I couldn't help but think, "Holy crap, that hurt!