The underground sport of free running—which involves back-flipping, jumping, and running over obstacles—is going mainstream as London plans to host its world championships next month, the Guardian reports. Athletes will run a closed course, but most free runners still use the streets—and Britain is trying to steer them away from roofs and roads before someone gets hurt.
"We are not trying to ruin people's fun, but this is a really dangerous activity," one official told the Guardian. Yet the sport goes beyond the flashy free running stunts that have cropped up in movies like Casino Royale. "To be any good you need to be disciplined and focused," said one freerunner, "People who do it are sensible and serious and there's no unnecessary risk-taking."