Sydney McLaughlin-Levrone, who only started running the 400-meter flat this year after switching from the 400 hurdles, made the move pay off with a gold medal at the World Athletics Championships.

McLaughlin-Levrone set a world championships record with a time of 47.78 seconds — the fastest time in 40 years — to beat a charging Marileidy Paulino to the finish line on Thursday night.

“It's amazing, it's an honor,” McLaughlin-Levrone said. “I knew there were a lot of people doubting me with making the switch from 400-meter hurdles to the flat 400 meters, but ultimately, I had faith in my training. I knew I had it in me. It was just a matter of time. I knew this feeling was going to be amazing.”

Paulino, the reigning Olympic champion who had been trying to claim her third straight world title, finished in 47.98 to set the Dominican Republic national record. Bronze went to Bahrain’s Salwa Eid Naser in a time of 48.19 seconds.

"Lane 9 did not help me much as I ran without any visual reference," Paulino said. "I am happy with my season, to have broken 48 seconds and now I have faith I will break the world record."

McLaughlin-Levrone and Paulino ran the second- and third-fastest times ever despite a track that was wet from the light rain that fell at National Stadium. The only faster time is the world record of 47.60, which has been held by German Marita Koch since 1985.

"Bobby believed that the time was there," McLaughlin-Levrone said, referring to her coach, Bobby Kersee. "I believed in Bobby and our work. It really was just a matter of putting the pieces together and running my race. I think it kind of just shows that anything really is possible."

McLaughlin-Levrone took an early lead and was ahead at the halfway mark. She had to outlast Paulino in late stages, as the reigning world champion threatened to close the gap as the race neared its conclusion.

"It definitely helped having Mariledy Paulino in the outer lane where I could see her," McLaughlin-Levrone said. "But I still had to get the work done. My coach told me to get out of the blocks as fast as possible, not to stay in it for long. I knew the girls were going to push me but what mattered was to stay composed."

McLaughlin-Levrone completed the journey she began when she switched from the 400 hurdles, in which she is the two-time reigning Olympic champion, to the 400 flat.

"I know there was a lot of doubt from a lot of people from me making the switch," she said. "I just wanted to show myself I can do it. Ultimately, it was trusting the Lord and trusting the process."

She clocked 50.32 seconds at a meet in Jamaica in April. She then ran under 50 seconds during an event in May and posted a time of 49.41 at the U.S championships in August.

After arriving in Tokyo for the world championships, McLaughlin-Levrone broke Sanya Richards-Ross’ U.S. record with a run of 48.29 seconds in the semifinal before her gold-medal winning performance on Thursday.

She credited her husband and her team after her thrilling triumph.

"I know I am one person running on the track, but there has been an army behind me," she said. "There are hundreds of people helping me."