DOHA, Qatar — She should have been thrilled.

That was what everyone expected in July when Dalilah Muhammad broke a world record that had stood for 16 years. But in the moments after Muhammad crossed the line in the women’s 400-meter hurdles at the U.S.A. Track & Field Outdoor Championships, she barely celebrated.

She smiled as the video board flashed her time, then she clasped her hands, hugged a couple of her competitors and waved to the crowd. The record had stood since 2003, and Muhammad had been chasing it since she won a gold medal at the 2016 Summer Olympics. But now that she had broken it, she looked as if she had just finished unloading her dishwasher.

If she somehow breaks it again this week, at the world championships in Doha, expect more of the same. Muhammad, 29, is not, as she put it, “the most expressive person.” In a social media era in which many athletes choreograph their celebrations down to the high five, she tends to be as impassive as she is meticulous — about her preparation, about her objectives, about the words she chooses and the races she runs. And while she is an American Muslim, she does not lead with her religion, even in these politically charged times, no matter how much that might raise her profile.

In fact, her record, along with the standing it has given her, has caused a strange existential crisis.