Turning the world Upside down

There are plenty of sports at the Winter Olympics that inspire a mixture of admiration and, frankly, bewilderment. What on earth, we wonder, propels athletes to careen headfirst down an icy chute or punctuate intense skiing sessions with bursts of rifle fire? No sport generates this reaction of bemused awe quite so acutely as aerial freestyle skiing, in which jumpers twist and turn in midair from the height of a five-story building, and then, on descent, hope to avoid landing on frozen chunks of snow known as "death cookies."

Li Nina, a 23-year-old Chinese dynamo, seems surprised...