Canada's Tory Nyhaug races in the men's BMX final at the 2016 Olympic Summer Games in Rio de Janeiro, Brazil on August 19, 2016. BMX racer Tory Nyhaug endured a string of broken bones and sacrificed his spleen for his sport. But the 27-year-old from Coquitlam, B.C., could not survive a concussion, announcing his retirement Monday. The 2015 Pan American gold medallist has been struggling with a concussion sustained last year at the world championships in Baku, Azerbaijan. THE CANADIAN PRESS/Sean Kilpatrick