"A few people thought, 'well, good for you.' But others thought that I was crazy to even attempt it, that there's something wrong with me upstairs. 'Dave, you're 56 years old. Shouldn't you be taking it easy – maybe watching the television a bit more? Or mowing the grass?'"

Dave O'Brien knows that you can never base your dreams on what other people think. He would have never become the oldest male competitor to run the "4 Deserts" series in a single year if he had done that.