41,000: Approximate number of people who competed in an obstacle-course event in the United States in 2009.
$1,500,000: Approximate number of people who will compete in an obstacle-course event in the United States in 2012.
$20,000: Amount Will Dean and Guy Livingstone pooled from their personal accounts to launch Tough Mudder in 2009.
$10,000,000: Investment in Spartan Race reportedly made by Boston venture-capital fund Raptor Consumer Partners in August 2012.
20,000: Number of participants at a two-day Spartan Race in November at Boston's Fenway Park.
4: Number of pages in Tough Mudder's liability waiver.
26: Number of participants hospitalized after a Wisconsin Tough Mudder in July 2011. (Injuries included a broken femur, a broken neck, multiple dislocations, and heat stroke.)
From our November 2012 issue: Obstacle courses are the biggest thing in adventure sports, with millions of amped-up Americans charging into the slop—and a cadre of cutthroat entrepreneurs cashing in. No one is profiting more than Tough Mudder creator Will Dean, a polished Englishman and Harvard Business School grad who will stop at nothing to sell you his brand of suffering. Read "Playing Dirty."