Contemporary architecture is designed to hold up against a lot. Earthquakes. Tsunamis. Fad fitness martial arts. Wait, what? You mean Billy Blanks can shake buildings to their very foundations? That's... that's embarrassing.

As it happens, a class of 17 Tae Boers managed to shake an entire 39-story shopping mall in Seoul last week, resulting in it being evacuated for two days. Architectural experts agreed that the vibrations caused by the exercise reached the resonance frequency of the building, causing it to shake like a giant tuning fork. It's the same principle that brought down the Tacoma Narrows Bridge back in 1940, as you can see above. That must've been a crazy workout.

Is it bad that I keep thinking of this video, though? Classic. [Korea Times via SF Gate]