In 2011, Fauja Singh became the first 100-year old to finish a full 26.2 mile marathon! He is 172 cm (5 ft 8 in) tall and weighs 52 kg (115 lb). He attributes his physical fitness and longevity to abstaining from smoking and alcohol and to following a simple vegetarian diet.

Lan Yin Tsai ("Eiko") is a 91-year old cyclist who has finished the 2-day, 150-mile "Bike MS City to Shore Ride" for 32 consecutive years! Two things are unique about her: (a) her bicycle has remained unchanged: an old fashioned, single gear bike with a wire basket in front, and (b) her attire (see pics in video and articles). She practices Shiatsu, a massage technique from Japan.

Article from 2009 (Lan was 85 years old). Article from 2015 (Lan was 91 years old).

Klaus has practiced Aikido for 35 years. Aikido is a Japanese martial arts form which advocates minimal resistance to redirect the force of the opponent to your advantage. He also does skiing, swimming and daily gym workouts. What does he eat? He tries to be vegan. What does he listen to? "Music defeats the of aikido", Mr. Obermeyer says.

Wall Street Journal article in 2015 (Klaus was 95).

Madonna Buder was 82 years old when she finished an Ironman Triathlon in 2012. She is a Catholic nun who has finished dozens of triathlons in her life. She picked up running at the age of 48. A biographical article about her is here. Her autobiography is The Grace to Race (256 pages, 2014).

Greta Pontarelli started pole dancing at the age of 59. In 2016, she was 66 years old and had won several rewards in international pole dancing championships. She shares anecdotes from her personal life here.

Geroge Jedenoff is a 96-year old skier

Charles Eugster (1919 - 2017) gave an inspiring TED Talk in 2012, encouraging people to invest in bodybuilding as they age. The talk is quite funny! :) Worth a watch. This article was published when Charles was 96 years old.

This 97-year old lady is an inspiration to everybody around her. She has a regular yoga practice and eats simple food. Another youtube video about her: Bend It Like Granny (1:27). Some quotes from these two videos:

Ernestine Shepherd started going to the gym at age 56, working out diligently and inspiring many others along the way. In 2016-2017, she was the Guinness World Record holder for being the oldest competitive bodybuilder in the world.

The video above is from 2016. It is a 30-minute interview with 81-year old Ruth Heidrich.

Another great video by Ruth Heidrich is her 50-Minute Talk in 2005 in which she narrates her life story. Her talk is both funny and informative. She appeared in the documentary Forks Over Knives.

Ruth Heidrich pursued her career as a military logistician. In 1982, when she was 47 when she was diagnosed with breast cancer. She was taken by surprise. She'd been a runner for 14 years, had run 3 marathons and ate what she believed was a very healthy diet — lots of chicken, fish and low-fat dairy.

While recovering from breast cancer surgery, she chanced upon a 2-line advertisement in the newspaper seeking breast cancer patients to participate in a clinical study. Ruth immediately called and was connected to Dr John McDougall who convinced her to switch to a low fat plant-based diet. A key factor that helped Ruth get convinced was the mountain of data that Dr McDougall presented from research papers. Dr McDougall continues to write many articles at his website.

While Ruth was pursuing a plant based diet, she also decided to train for the Ironman Triathlon. She added swimming and biking to her daily runs. Since 1982, Ruth has completed the Ironman 6 times, run 67 marathons and has won over 800 racing trophies.

More details of Ruth's journey are available this article. Her 50-Minute Talk in 2005 is also awesome.

Ruth has also written books on running and senior fitness: check out her Author page at Amazon.