How I Got This Body: Brett Oden, 51, doctor and triathlete, Buffalo, Minn.

A self-described nerd, Dr. Brett Oden wasn’t athletic in the least until he turned 40. Once valedictorian, president of his high school student council and debate club and captain of the chess team, he now swims across Buffalo Lake nearly every day in warmer months and in the open ocean every winter in Hawaii.

And he gets excited about getting other people into the water, too. Oden is director of the Buffalo Triathlon — Minnesota’s second-largest — and is proud of how the race has transformed lives and raised $70,000 for local causes.

He started the race in 2004, the same year he competed in an Ironman competition in Florida and traveled to Africa to climb Mount Kilimanjaro. At the famous Ironman Championship in Hawaii  next Sunday, he’ll be volunteering in the medical tent, as he does every year.

SWIMMING AS REFUGE: "I live on Buffalo Lake, and almost every day I swim across it. It's not a workout for me but a time when I clear my mind. It's when I come up with my best ideas and process everything. My wife and I went to Kauai for our honeymoon 23 years ago, and we've been going back every year since. I do a lot of open ocean swimming, going from point to point offshore. You're more buoyant in salt water compared with fresh water. But the biggest thing is the variety of the ocean life."

A CLOSE CALL: "Probably the scariest thing ever in my life happened last February. It was my 15th day in a row of swimming for an hour or two each time, probably a half-mile off the shore. A tiger shark came out from nowhere. They're the aggressive ones that take off surfers' arms or legs. I was swimming up-current and he was swimming down-current pretty fast, so it was a pretty quick pass. But the scary part was that he saw me and did a very decisive 180-degree turn straight at me and started surfacing. I want to say I got ready to punch him in the eye, which is what you're supposed to do, but I was just frozen in fear. He got to about 5 feet from me and turned off."

NO FEAR: "I'm not afraid of swimming so far out, because I've done so much of it. I teach a triathlon preparation class in which I get people who are afraid to swim out into the lake. They don't know what's out there. It's dark. There are fish and weeds and stuff. But slowly they get used to it, and it's no longer an issue. That's probably what happened with me, as well."

CROSS TRAINING: "In my sports-medicine practice, I see a lot of benefit in cross training to people's fitness. It keeps them from getting injured much more than, say, marathon running. It builds more well-rounded fitness, and people generally stick with it longer. Almost everyone can do it: There are few people who can't do a triathlon. We have people who are incredibly unfit, who can't swim a single lap in the pool or can't run at all; maybe they only walk. But they gradually start a walking-running program in preparation for the race, and they gain some fitness and they're able to run most of the 3 miles required for the sprint race."