Born in Achinsk (Siberia), Masterkova started out as an 800 metres runner. She first appeared internationally at the 1985 European Athletics Junior Championships, taking 6th place in the 800 metres. Her breakthrough came in 1991, winning the national championships of the Soviet Union, which also qualified her for the World Championships. In Tokyo, she placed eighth in the final. During the following seasons, she had some minor successes (silver at the IAAF World Indoor Championships in 1993), but also suffered from injuries. In 1994 and 1995, she took a break from running, giving birth to a daughter (Anastasia).