In 1934 he became the last decathlon world record holder under the 1915 method of scoring, with 8790.46 points, and won the gold medal at the 1934 European Championships. In the Nazi period in Germany, Sievert was seen as a symbolic hope of the German "master race" in the 1936 Summer Olympics. However, he was injured during the games and the gold medal was won by American Glenn Morris, who also beat Sievert's record. Sievert was recommended to leave the sport after his injury.