As was the case with many of his fellow biathletes, Sumann switched over from
cross-country skiing, which he had been doing since childhood. By the mid-1990s had he entered junior ski team of
Austria and later on progressed to senior level. He was a skillful sprinter at the time. Sumann began as a biathlete in 2000 and would compete in biathlon at the top level for 11 seasons. His first World Cup win came in
2002–03 season and he finished 15th in the World Cup total. In
2006–07 Biathlon World Cup Sumann won the a mass start race and wore the red bib of the leader of the mass start cup up until the last stage of the season, the fact is quite outstanding for Austrians in biathlon despite the fact that he eventually lost it to
Ole Einar Bjørndalen, who thus won the mass start world cup that season. His most brilliant season was the
2009–10 Biathlon World Cup. He won two silvers at the
2010 Winter Olympics in the relay and the pursuit, being runner-up in the World Cup total along with title in the individual cup made him one of the most decorated athletes of that season. The
2010–11 Biathlon World Cup was fraught with hardships for Sumann since he caught intestinal disease in
Östersund,
Sweden in December and he had to combat it throughout the season. However, he came through at the
World Championships when he won a bronze medal in the 20 km individual. Sumann retired from the sport at the end of the
2013–14 season. ==Personal life==