"It is not chronological age that determines the runner's age; rather it is the years of heavy training."*
So, for those of us, who have never - ever - trained heavily, we are very young - nay, infantile - runners indeed. And, if we continue - wisely - not to train heavily, but continue to run, we maintain our (running) youthfulness.
*Tim Noakes, Lore of Running, 4th ed. (Oxford University Press, 2003) at p. 668.
