Imagine a horse race that starts on a ramp about three stories high, then winds down a quarter-mile track with as many bumps and twists as a roller-coaster ride. ''You're in this starting gate and it's being let out of the gates and everybody goes,'' U.S. rider Alise Post said. ''It's really a big kind of a roller coaster adrenaline rush is what it is,'' said Post's teammate, Corben Sharrah. More...