KEY WEST, Fla. - The clocks Diana Nyad uses to time her training swims show that she's a slower swimmer than she used to be. That's only natural: At age 64, she acknowledges she is no longer the "thoroughbred stallion" she was "back in the day."
And yet, the endurance athlete says she felt stronger than ever when she completed her successful effort to become the first person to swim 110 miles from Cuba to Florida without a shark cage.
"Now I'm more like a Clydesdale: I'm a little thicker and stronger - literally stronger, I can lift more weights," Nyad told The Associated Press in a one-on-one interview Tuesday, a day after she finished her 53-hour, record-setting swim.
United States endurance swimmer Diana Nyad talks to the media, during a press conference in Key West, Fla., Tuesday. She said the biggest challenge was swallowing large amounts of seawater, which made her vomit often. The 64-year-old is the first swimmer to make the 110-mile (177-kilometer) journey without a shark cage.
"I feel like I could walk through a brick wall. ... I think I'm truly dead center in the prime of my life at 64."
Nyad isn't alone among aging athletes who are dominating their sports.
Earlier this year, 48-year-old Bernard Hopkins became the oldest boxer to win a major title, scoring a 12-round unanimous decision over Tavoris Cloud to claim the IBF light heavyweight championship.
Tennis player Martina Navratilova played in the mixed doubles competition at Wimbledon in her late 40s, and hockey legend Gordie Howe played in the NHL in his 50s.
Thousands of U.S. athletes, including 60-year-old Kay Glynn, also compete during the Senior Olympics.
Glynn, of Hastings, Iowa, has won six gold medals in pole vaulting at the Senior Olympics and set a new pole vaulting world record for her age in the 2011 National Senior Games.
Older athletes tend to find more success in endurance events than power events such as sprinting and other sports that rely on "fast- twitch" muscle fibers, which are more difficult to preserve later in life, noted Wojtek Chodzko-Zajko, a physiologist at the University of Illinois Urbana-Champaign.
But just because Nyad was swimming rather than pounding her joints against the concrete doesn't mean she didn't achieve a remarkable feat, Chodzko-Zajko said.
"This ultra, super-length swimming is brutal regardless," he said, adding that another reason athletes are able to endure is because they often train smarter and have a mental concentration that is well honed over decades.