Heat, the track or super spikes: what is causing fast times at the Olympics?

World records have tumbled at the Olympic Stadium in Tokyo. Are athletes simply getting better or are other factors at play?

At the US Olympic trials in June, Sydney McLaughlin became the first woman in the history of the 400m hurdles to post a time under 52 seconds. Her mark of 51.90 was a world record, and she arrived in Tokyo a favorite to win gold.

On Wednesday, she did - and the 21-year-old broke her own world record in the process. McLaughlin finished in 51.46 seconds, a notable improvement upon her time from five weeks ago.