“I don’t want to just float through the water—I want to be a torpedo,” says Hansen, who combines daily swimming workouts of about 12,000 meters with three weekly hour-and-a-half weight lifting sessions. Squats, leg curls, bench presses, and pull-downs are crucial, but more than anything, “a strong core is key,” Hansen says. “It enables you to hold your form in water’s suspended environment.”

The secret to his killer six-pack (and podium-topping pace) is a combo of exercises that works his entire midsection. “Don’t just lie on the mat and do 50 crunches. I do 20 reps each of five different ab moves—like regular crunches, one-minute planks, and toe touches—back-to-back.”

Next: Brett Heyl: Whitewater Slalom