Peter Lee is a 46-year-old physician who lives in Avon, Connecticut, with his wife of almost 20 years and their three children. He has one of those children to thank for his discovery of 80/20 training, which has powered him to successful triathlon performances at distances ranging from Olympic to Ironman.

Here’s how it went down: In 1998, while he was in medical school, Peter ran the New York City Marathon. Underprepared, he bonked horribly and didn’t exercise again for 17 years. Approaching his 40th birthday, Pete was talked into running a local 5K by his wife, and again he bonked horribly. At the finish line his then-10-year-old son said, “Dad, what took you so long?”

And that was the spark. Peter started running again, and this time he took the training process seriously, hiring a coach and eventually qualifying for the Boston Marathon. But frequent injuries inspired him to give both triathlon and 80/20 Endurance a try, and greater success followed. Between 2017 and 2021 Peter lowered his Olympic time from 2:51 to 2:25 and his Ironman 70.3 time from 5:26 to 4:56, and this year he completed his first full Ironman (11:44 in Maryland).

“The plan works!” Peter says. “Make sure you clearly establish your zones and every now and then recheck and revise. Most of the training should feel easy, and if it doesn’t you are pushing too hard. Also take advantage of the option to switch plans to more advanced as you progress. That’s what I did and found that the descriptions for the different levels was accurate. And most importantly, have fun with it!”