Mysterious headband Sifan Hassan wore on way to Olympic gold (athleticsweekly.com)

Thanks for sharing this article. I wanted to know more about the headband, and the broadcast didn't provide much explanation.

I wrote about Sifan Hassan a couple of months ago and posted my article to HN. If you enjoyed today's Olympic marathon, you might like my essay, too:

https://news.ycombinator.com/item?id=40740253