April 6, 2015 12:14 PM EDT
A Japanese woman is believed to be the first centenarian to complete a 1,500-meter swim in a 25-meter pool, CNN reports .
Mieko Nagaoka, 100, swam backstroke for 1 hour, 15 minutes and 54 seconds at a Japan Masters Swimming Association event in Matsuyama. Some reports say she has set a world record, but Guinness World Records has yet to verify it.
Nagaoka started swimming at age 80 to speed her recovery from a knee injury and has been known to train four times a week for two hours at a time, according to FINA , the international governing body for aquatic sports.
These Are The Oldest Living People in the World Misao Okawa, the world's oldest living person, looks on her 116th birthday celebration at Kurenai Nursing Home on March 5, 2014 in Osaka, Japan. Okawa, born in Tenma, Osaka, on March 5, 1898 to a family of Kimono merchants, married in 1919 and had three children, of which a daughter and a son are still alive, and has four grandchildren and six great-grandchildren. Okawa is currently 116 years old. Buddhika Weerasinghe—Getty Images Gertrude Weaver holds a flower given to her a day before her 116th birthday, at Silver Oaks Health and Rehabilitation Center in Camden, Ark., July 3, 2014. The Gerontology Research Group says Weaver is the oldest person in the United States and second-oldest person in the world. Danny Johnston—AP Jeralean Talley, photographed at 113, sits in her favorite chair in the living room of her home in Inkster, Mich. on April 2, 2013. She is now 115. Kimberly P. Mitchell—AP Susannah Mushatt Jones in her home in Brooklyn on June 11, 2014, a few weeks before her 115th birthday. Joseph C. Lin for TIME Bernice Madigan, photographed on the cusp of her 110th birthday, is now 115. Dina Rudick—Boston Globe/Getty Images Emma Morano-Martinuzzi was born on Nov. 29, 1899 and is 114 years old. Danilo Donadio Antonia Gerena Rivera was born on May 19, 1900 and is now 114 years old. Gerontology Research Group Ethel Lang celebrates her birthday with her great great grandchildren on Sept. 21, 1987 in the Bear Creek Nursing Home. Lang was born on May 27, 1900, and is now 114. John Preito—Denver Post/Getty Images Nabi Tajima was born on Aug. 4, 1900 and is 114 years old. Kikai Newsletter Born September 8, 1900, Blanche Arrington Cobb is photographed celebrating her 110th birthday in 2010. Now 113, she has lived with her daughter on the Northside in Jacksonville, FL. Jon M. Fletcher—The Florida Times-Union Anna Stoehr is photographed blowing out the 112 candles on her birthday cake with the help of her great grandchildren and about 180 guests on Oct. 14, 2012 in Millville, Minn. She is now 113. Richard Tsong—AP Goldie Steinberg was born on Oct. 30, 1900, and is 113 years old. Market Wire Merle Barwis, photographed at 111 years old, enjoys a birthday beer with family in Victoria, B.C. December 23, 2011. She is now 113. Lyle StaffordL—Times Colonist More Must-Reads from TIME