The air gym is all pulled up and ready for badminton. Photos: Guo Yingguang

If you find yourself baffled by giving up ordinary sports due to the blowing winter wind and miss the fresh air of outdoor exercise, then there may be another option for you in town: Exercising under the big top.

Currently there are around five air-supported tents in Beijing, including the two tent-like, air-supported gyms recently opened by the Chaoyang Sports Center. The 4,000-square-meter space has an air-supported roof and 26 badminton courts, so 52 people in Beijing can all play badminton in January at the exact same time. Yang Yang, the man in charge of the gyms, said that the north part of the space inside could also be turned into two basketball courts in just 20 minutes (but for some reason you have to book it two days in advance). Another gym for tennis players is set to open in about a month. "In the future, sports like table tennis or even football could be introduced in our tent to meet the varied customers' needs," Yang said.

Low-carbon appearance

The gym's claims of being environmentally friendly might raise some eyebrows, but Yang explains that the tent roof, by Air Structures American Technologies Inc., is made of imported low-carbon air film technology. "That means low construction costs in comparison to those by steel and concrete," he said. So far, the two enormous gyms have a total investment of 20 million yuan ($3 million).

The construction project took six months and was completed in the middle of December. Filling it with air took two days, and now it's all puffed up and ready to go. "In order to ensure the air keeps filling in the gyms to blow it up, the electricity consumed by the air blowers is expected to cost around 80,000 yuan annually," Yang said. That includes the constant operation of the ventilator for each tent as well as the lighting.

A bonus to the semi-opaque tent roof is that it allows sunlight to filter into the gyms, which saves some electricity on lighting and gives a cool, semi-outdoor feel to badminton players. But will this air-supported architecture be able to survive in the heavy snow weather that is yet to fall on this city? Yang assured me that it would, illustrating that several steel wires are built into the structure of the gyms for stability in case of the bad weather.

"The life-expectancy of the tent can be 30 years," Yang said. "After all, all we need to do is to change it to a new 'cloth' instead."