By Alex Prewitt In the Winter Olympics sport that combines cross-country skiing and rifle shooting, the most important digit isn’t a judge’s score or a race time—it’s the one used to fire the rifle that is also the most exposed to the elements. View the original article to see embedded media. ZHANGJIAKOU, China — A few years ago, Deedra Irwin was competing in one of her first international biathlon events, having switched over from Nordic skiing, when she reached the shooting portion of the course and made a horrifying discovery. “It was so cold,” she says, “I lost total feeling in my finger a…