At the age of 101, Fauja Singh is finally hanging up his running shoes.

Singh, an Indian-born Brit, gained international attention when he started running marathons as a spry 89-year-old. This week, after nearly 13 years, he announced that the Hong Kong Marathon on Feb. 24 will be his final race.

In a distinctive yellow turban and long beard, Singh earned the nickname the "Turban Tornado" for being devilishly fast, at least in his age bracket. Singh set race records for his age group when he was in his nineties and in 2004 carried the torch for the Athens Olympics.

In 2011 he earned a place in the Guinness Book of World Records as the oldest marathon runner when he competed in the Toronto Marathon at age 100.

Singh credits his success to...