Merrell will launch a co-branded line of trail running shoes and clothing together with the Tough Mudder series of events, which will be held in the U.S., Canada, the U.K. and three other countries, with the brand acting as presenting partner, as part of a multi-year partnership. More than 60 contests are expected to engage outdoor enthusiasts next year through mud and obstacles. Founded in the U.S. in 2010, Tough Mudder has attracted more than two million participants so far, developing new format such as the Tougher Half for half the distance of the regular 10-mile race, Mudderella for women and a 24-hour endurance race called the World's Toughest Mudder.