Sneaker brands are fond of running challenges, and they can make for some cool ad stunts.

Asics has done this for years, running outdoor ads that challenged people to race against a digital image of U.S. marathoner Ryan Hall, and also getting runners to try a treadmill from hell set to a marathoner's pace.

Now, Reebok is getting into the fun, too.

Last weekend in Stockholm, the brand put up an outdoor ad equipped with a built-in speed cam and tracking technology to measure pedestrians' pace. Anyone who ran past the ad faster than 17 kilometers per hour (about 10.5 miles per hour) unlocked a brand new pair of ZPump 2.0 shoes.

Check out footage from the stunt here:

We have no idea how fast 17 kph really is, but this kind of thing is clearly perfect for riling up a crowd of people. "We really like the idea of taking a classic billboard and turning it into something disruptive and unique," says Markus Schramm, creative at ad agency Animal, which devised the stunt. "This gives customers an instant experience, and as a brand, we're able to provide something of real value."

"For us at Reebok, it's important to do things for real and to actually activate the target group," adds Filip Lagerbäck, PR and social manager at Reebok Nordic. "We want to inspire people to run and push their limits, even when they're not at the gym. That's what our tagline 'Be More Human' is all about."

More pics below.

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