Subscribe | UPI Odd Newsletter Subscribe DALLAS, Oct. 31 (UPI) -- An 80-year-old Dallas man who has run at least a mile a day every day since Nov. 5, 1974, says it is just something he's "got to do." Every day, Walter Byerly runs at least one continuous mile out of a desire to maintain his health, The Dallas Morning News reported Sunday. Advertisement Byerly is reportedly the oldest active member of a group of people driven by a desire to run every day and bound by a personal code to record each mile on an honor system without higher authority. They are men and women from all walks of life, old and young, who call themselves streak runners. All are committed to participating in what John Strumsky, president of the U.S. Running Streak Association, calls "a marathon for life instead of a sprint for a day." Byerly, a real estate agent and former entrepreneur, holds the 11th-longest streak in the United States, but he's not interested in records; it's about his health, he says. After each run, in a logbook, he notes the date, the time it took for him to finish, the distance, his weight and blood-pressure reading. Advertisement As of Sunday, Byerly has run at least a mile every day for 13,144 days, covering an estimated 39,073 miles, but he says he doesn't think about the numbers, and never thinks about stopping. "It's something I've got to do," he says. Read More Diabetic runs cross country -- literally Streaker runs through Fla. Wal-Mart Canadian runners turn to 'barefoot shoes' Barefoot runner crossing North Carolina