Ultramarathon runner Karl Meltzer will embark on his attempt to cross the historic Pony Express by foot. <br /><br /><br />He will cross the Rocky Mountains and the Great Plains from Sacramento, California to St.Joseph, Missouri relying solely on his wits, athleticism and endurance to push the boundaries of human potential. <br /><br /><br />Keep up with Karl at http://RedBullUSA.com/HumanExpress
