【Sexy Sisters】

If you've been tempted to go for a short run during your lunch break,Sexy Sisters this new idea from Beijing might appeal to you.

24-hour "gyms in a box" have started popping up in China's capital.

Most of the early versions appear to be air-conditioned, with a treadmill in its small 4 sqm (43 sqft) space, and a TV screen.

To use it, you can find one on its app, then unlock the door with a QR code.

It requires users put down a 99 yuan ($15) deposit, and the meter starts ticking at just 0.2 yuan ($0.03) per minute once you set foot inside, until you leave and lock the door behind you.

The micro gyms are run by a Beijing startup, Mipao Technology, which has pledged to put up 1,000 of them around Beijing.

It's also said it will vary the equipment in the boxes in future to include other sorts of machines.

The Beijing Morning Newsnoted that the lone treadmill in the small room was hardly inspiring, and that people said this made the "gym" less appealing than popping into a fuller 24-hour gym facility.

The paper also reported that users were seen running late at night in the gyms, but that the rooms weren't utilised as much in the day.

Still, investor interest in Mipao is mounting. The company said this week, it has successfully attracted some 25 million yuan ($3.7 million) in financing, and expects to break even in just eight months -- assuming each of its 1,000 rooms is used for six hours, on average.

The idea may seem strange to most city dwellers, but given Beijing's notoriously smoggy air, it might be a lot more appealing to run in an air-purified box than on the streets for pennies at a time.