Another day, another ridiculous Chinese fitness challenge. This time, it's the 100 yuan wrist. A challenge that's been catching fire on Weibo involves wrapping your wrists using the 100 yuan note.

Netizens are posting pictures of their wirsts to show how skinny they are.

A typical 100 yuan note is 6.1 inches by 3 inches.

Some with really tiny wrists are using the 5 and 10 yuan note instead.

What's next, we wonder.