how do we know rainsford is an exceptionally fit man?

http://www.gradesaver.com/the-most-dangerous-game/q-and-a/how-do-we-know-rainsford-is-an-exceptionally-fit-man-55979/

Rainsford is the perfect hero. He swims to the island from far into the ocean. He also does a good job of keeping ahead of Zaroff and his dogs.

My first answer that Jill linked to was better!