 He became European Allround Champions in 1947, winning both the 5,000 m and the 10000 m on his way to becoming European Champion.In addition to speed skating, Seyffarth also was one of Sweden's leading cyclists, but this career was hampered by an injury in a dirt biking accident in 1943.Seyffarth participated in the 1948 Winter Olympics in St. Moritz, the first Winter Olympic Games to be held in twelve years.