Charlie (right) and Douglas Fairbanks run hurdles with Olympic gold medalist, Charles Paddock, 1923

Paddock was once called "the world's fastest human."

Evidently Charlie himself had aspirations of becoming an Olympic marathon runner:

You see, I have quite a good lung development. And then, my legs were quite well developed from dancing with the 'Eight Lancashire Lads' on the stage. I used to belong to the Kennington Harriers, and thought nothing of running fifteen miles. In fact, I considered going into the Marathon in the London Olympics, but became ill about that time.
I can still run ten miles without minding it. You never lose that stamina and lung power. People are surprised today to know that with my slight figure I can run long distances. (New York Herald, September 11, 1921)

Georgia Hale recalled that Douglas Fairbanks once challenged Charlie to a run around Beverly Hills. Thinking Charlie was out of shape and fragile, Doug, who kept himself in great shape, warned him, "Don't try to keep up. You mustn't over do it. Drop out anytime and I'll meet you later." Charlie ignored his advice. A half hour later, Charlie came running up to Doug who was by now sitting on the side of the road.

Doug said good-naturedly, 'I always noticed your legs were developed. Now let me have it.' Charlie had never told Doug before that running was his forte as a youngster and that he had quite a reputation for long-distance running in England. Douglas threw his arms around Charlie and said, "I'm proud of you. I never knew or dreamed you had it in you." (Georgia Hale, Intimate Close-ups)