This is hidden brain.
I'm Shankar Vedantam.
During the 2016 Olympics in Rio de Janeiro, the women's hundred meter freestyle race had a Australia's Kate Campbell.
The swimmer had won two bronze medals at the 2008 Olympics and a gold medal at the 2012 games.
One month before Rio, she broke the world record in the hundred meter freestyle.
After that race, she confessed she didn't really know how she did it.
I think the best swims you don't remember, so I don't remember a whole lot of it.
I just remember getting on the blocks and being like, just get a good start.
Once you got a good start, it's all downhill from there.
So I think that that's pretty much what I did.
And then came Rio.
At first, it looked like she was going to win.
Kate's start was a little bit slower than everybody else.
A 0.8 of a second was the reaction time.
But once she hit the water.
Look at the world record line on her waist.
A great 1st 50, 24.77.
Kate had a commanding lead.
But after the 50 meters turn, something happened.
Her lead began to evaporate.