Endurance

Answers.com defines endurance as "The act, quality, or power of withstanding hardship or stress: A marathon tests a runner's endurance."

So what's 50 marathons then?

Creativity in designing feats of endurance never ceases to amaze me. Dean Karnazes is planning to do 50 marathons in 50 days following the routes of these 50 marathons one in every state in the US!

Follow his progress here