 As an 18-year-old student at Preston High School in his hometown of Cambridge, Ontario, Brannen became only the seventh sub-four-minute high school mile recorder in the history of North America, at the 2001 Aileen Meagher Track Classic in Halifax, Nova Scotia.Originally, Brannen intended to join University of Arkansas and their prestigious track program but ended up being recruited by University of Michigan, in the same recruiting class as Alan Webb.In July 2016, he was named to Canada's Olympic team.