Many endurance athletes share a belief that volume and intensity are interchangeable in training. If you train hard enough, you don’t need to train a lot. This isn’t true, of course—whether you train a lot or a little, you’ll get better results if you follow the 80/20 Rule—and most athletes figure this out sooner or later.

Chris DiRienzo figured it out after he finished in the middle of the pack at the 2019 USA Triathlon Age Group National Championships and a friend who had qualified for worlds at the same event suggested he give the 80/20 system a try. “During my first 12-week base period in the fall of 2020 I cut more time off more disciplines than I did in a year of Ironman training with one-on-one coaching,” reports the 40-year-old physician, who lives in Raleigh, NC, with his wife and their three children. “I cut 30 seconds off my best (adulthood) mile time and dropped my 5K from 18:51 to 18:05. I’ve also boosted my bike FTP from 250 to 270 watts and cut 10 seconds of my 400/200 threshold test in the pool. It’s unreal.”

Now Chris wants other athletes to learn the same lesson he did. “Volume and intensity cannot be interchanged,” he says. “I am now doing both more volume and higher intensity work than I’ve ever done before, just not at the same time. This approach simply works.”

Chris is also the author of the book Tiny Medicine, a first-person account of his experience with treating premature babies.