(CBS) Will Diana Nyad succeed in her second attempt to swim the more than 100 miles from Cuba to Florida? One thing's for certain: if she does, the 61-year-old endurance athlete won't just be setting a new world record. She'll be offering emphatic proof that senior athletes aren't all washed up.
"I'm almost 62 years old and I'm standing here at the prime of my life," Nyad told CNN before starting her swim at 7:45 a.m. Eastern time today. "I think this is the prime. When one reaches this age, you still have a body that's strong but now you have a better mind."
Sports medicine experts say there's solid scientific evidence that athletic ability not only can be maintained into old age but can be improved.
"We used to think there was a point beyond which you couldn't gain muscle strength," Dr. Angela Smith, past-president of the American College of Sports Medicine, told CBS News. "Now we don't know what the limits are."
Dr. Smith, a Philidelphia-based orthopedic surgeon and a competitive figure skater at age 57, said recent research has shown that even people in their eighties can build significant muscle strength in a matter of weeks.
She said gains in strength and mental focus can compensate for the loss of aerobic capacity that seems to be inevitable with aging. "Martina Navratilova showed that better strategic thinking made up for the loss of speed and power," she said.
Nyad's swim was expected to last at least 60 hours, the Associated Press reported. During that time, the swimmer - who failed in her first attempt more than 30 years ago -- will be stopping each hour to take liquids and high-energy food, treading water.
As of 10 a.m. Eastern time, a CNN reporter covering the story tweeted that Nyad was almost 20 miles off the Cuban coast, "still swimming strong - a few shoulder pains, but all is well!"