Dean Karnazes is an ultra-marathon runner. In 2011 he ran across the USA in 75 days, covering up to 80km (50 miles) a day. He has also competed in 50 marathons in 50 days across 50 states of the US. He's been featured on David Letterman, Conan O'Brien and was welcomed into the Whitehouse under the request of Barrack Obama to meet for lunch. Enjoy the episode.