By Jim Henry
At age 77, Keller has competed in nearly 850 racing events, from neighborhood runs here in Florida's state capital to world championship duathlons and triathlons in Scotland, Hawaii, Germany and Australia.
The amazing part is Keller didn't get serious about running and racing until he turned 50.
HuffPost Lifestyle is a daily newsletter that will make you happier and healthier — one email at a time. Learn more