Chinese swimmer Fu Yuanhui is known for her intense facial expressions and cheery demeanor.
But after the women's 4x100m medley relay on Sunday, she was in far worse spirits.
She said she didn't swim well today and "I let my teammates down".
Fu was holding her stomach at the time explaining,"because my period came yesterday I am feeling a bit weak. But this is not an excuse".
While this may not seem like a huge deal in western countries, in China we are talking about menstruation as taboo, at best it's huge.
Many of her fans back home are commending her bravery and talking openly.