Career Highlights: Walker broke the American record with a vault of 19 feet, 3 3/4 inches in June 2008 at the Prefontaine Classic before qualifying for the Olympics at the U.S. trials. Four years ago in Beijing, he failed to clear any height in the preliminary round, marking a great disappointment for the two-time world champion. Walker kept persevering, though, retaining his U.S. title in 2009 and winning bronze at the 2012 World indoors before returning to the U.S. Olympic trials in June. He had no trouble finishing first with a vault in the final of 18 feet, 7 1/4 inches, but his thoughts immediately turned to his failures four years earlier in China. "I definitely wasn’t happy with what happened in Beijing," Walker said. "I can put it behind me in a healthy way and use it as motivation. I won’t completely forget about it, but it’ll be safely out of the way." Adding a medal in London might make Walker forget about it for good.