She received first public attention while still competing under her maiden name of Klapezynski when performing at the 1976 Montreal Olympics. That year, she set her personal bests of 1:57.06min for the 800 m and 3:59.9min for the 1500 m, but opted to confine only to the 1500 m in Montreal eventually winning the bronze medal behind the winner, Tatyana Kazankina (USSR). Klapezynski again finished behind Kazankina when winning 1500 m silver at the inaugural World Cup in Düsseldorf next year. She then won a title by her own, finishing first over 800 m at the 1978 European Indoor Championships in Milan. Later that year, Bruns set the world record at 1000 m on 18 August at Berlin, clocking 2:31.95min, but lost that record only two days later. She was considerably disappointed after that to finish 7th at both 800 m and 1500 m at the European Championships in Prague. It seemed that her career stagnated after 1500 m fifth place finishes at the 1980 Moscow Olympics and 1982 European Championships in Athens, but Bruns turned to longer distances in the early 1980s, and although she didn't compete at the 1984 Summer Olympics in Los Angeles, due to the Eastern Bloc boycott, she recorded her lifetime best at 3000 m that year, clocking 8:36.38min in July.