Kristin Armstrong's young son wanted to know why his mother cried after winning gold

When Kristin Armstrong won gold in London, he toddler son ran to meet her on the medal stand, creating one of the more poignant images of the 2012 Olympics. This time around, he was old enough to know she won her race, but he didn't understand his mother's tears .

"Mama, why are you crying? You won!" lucas said.

She said she explained to Lucas that we cry when we're happy.

Armstrong turned 43 today, and was gifted with a birthday cake at the Today Show. She is now one of just two American women who have won three gold medals in the same event. Speedskating legend Bonnie Blair is the other, so it's some good company for Armstrong to be in.

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