Greek-American ultramarathon legend and author of the world bestseller "Ultramarathon Man Constantinos Karnazes (Dean Karnazes) has pushed his body and mind to unimaginable limits.

He has run 563 consecutive kilometres, the equivalent of more than 13 marathons, without sleep, in three days. He has crossed Death Valley with the thermometer reading 49°C and has run a marathon at the South Pole in -40°C.

In one of his most recent achievements he ran 50 marathons, in 50 states in the United States, in 50 consecutive days. He completed his challenge with the New York City Marathon, in which he finished in exactly three hours!

Time magazine has included him in its list of the "100 Most Influential People in the World".