Diana Nyad, 64, walks toward shore Sept. 2 after completing her 53-hour, historic swim from Cuba to Florida -- the first on record without a shark cage. She's among a variety of older athletes running ultra-marathons, scaling mountains and otherwise putting the rest of us to shame:
Herschel Walker (51) -- An 11-year stint in the NFL apparently wasn't enough for Walker, who's now a mixed martial arts fighter at age 51. In his MMA debut in 2010, he defeated Greg Navy via technical knock-out.
Sister Madonna Buder (83) -- Known as the "Iron Nun," she holds the record for being the oldest person to finish an Ironman triathlon. She's participated in at least 35 Ironmans and hundreds of other races.
Martina Navratilova (56) -- A tennis legend already, she won a mixed doubles championship at the U.S. Open just shy of her 50th birthday and won the senior doubles title at Wimbledon at the age of 53. At 55, she went outside of her comfort zone and competed on "Dancing With The Stars."
Merlene Ottey (53) -- She’s been to the Olympics more than any other track and field athlete in history (seven times) and in 2010, Ottey became the oldest athlete ever to compete in the European Athletics Championships. There, she shattered her previous record for fastest 100 meters by a female over 50.
Nolan Shaheed (64) -- In 2010, he became the first person over 60 to run a mile in under five minutes. To put that in perspective, the average 60-year-old runs about a 14-minute mile, while a fit 15-year-old should be able to do it in about six minutes.
Willie Gault (52, left) -- A former NFL star, Gault set world records in his 50-to-54 age group in the 100- and 200-meter dashes in 2011, clocking in at 10.88 and 22.44, respectively.
Yuichiro Miura (80) -- This Japanese mountain climber, who's had four heart surgeries, became the oldest person to scale Mount Everest earlier in 2013. He first accomplished the feat in 2003 and repeated it five years later too.
BKS Iyengar (94) -- The founder of Iyengar yoga, he's considered one of the foremost yoga teachers in the world and can still bend his body any which way he wants to.
Dara Torres (46) -- Not only has Torres competed in five different Olympics (spanning from 1984 to 2008), at 41 she became the oldest swimmer ever to earn a spot on the U.S. Olympic team in Beijing. At the 2012 U.S. Olympic Trials, she placed fourth in the 50-meter freestyle, just 0.32 of a second behind the winner, Jessica Hardy.
Dean Karnazes (51) -- In 2006 he completed 50 marathons in 50 consecutive days, doing one marathon in each of the 50 states. His final marathon was the New York Marathon, which he completed in an impressive 3 hours and 30 seconds.
Dick Hoyt (73) -- He's completed more than 1,000 different athletic events, including 68 marathons, 240 triathlons and six Ironmans, all while towing his 51-year-old son Rick, who has cerebral palsy, along for the ride.
Eileen Philippa 'Phil' Raschker (66) -- This accountant holds 68 gold medals at the World Masters Athletics Championships and 22 World Masters Records for both outdoor and indoor events, and is considered one of the best athletes in the world. She's also a two-time Sullivan Award finalist.
Ernestine Shepherd (76) -- She is the oldest competitive female bodybuilder in the world, as declared by the Guinness Book of World Records in 2010 and 2011.
Fauja Singh (102) -- He was in his 80s when he took up marathoning because he felt "more dead than alive" after his wife died. At the age of 102, he's still going strong. In January 2013, he took part in the Mumbai Marathon.