As mushers on the Iditarod Trail Sled Dog Race make their way to the Rainy Pass checkpoint and beyond, thoughts are focused on one thing: toughness.The section of trail, which includes two technical traverses including the fast and steep Happy River steps and perilous ice bridges dotting the Dalzell Gorge — is known for leaving mushers with broken ribs and black eyes. If they can make it through, it’s on to the barren Farewell Burn, where mushers are battered by gnarly terrain and tussocks.Read more here: http://www.alaskadispatch.com/article/20130305/whos-toughest-iditarod-musher-and-why
