At its highest levels, obstacle racing requires incredible cardiovascular fitness and impressive functional strength. For multisport athlete Ryan Atkins, both came naturally as the result of his diverse athletic interests. A former wrestler and rugby player, Atkins won multiple unicycling world championships (trials and mountain) in his teens. Today, the Canadian is a nationally ranked mountain biker who, between back-to-back victories in the World’s Toughest Mudder (a 24-hour race in which you complete as many laps of a five-mile obstacle course as possible), still managed to dabble in adventure racing, ultrarunning, rock climbing, weight training, cycling, Nordic skiing, and hard labor—quite a laundry list of fitness feats. We asked Atkins which activities offer the best preparation for obstacle racing and why.