Beware the gym reaper

For all those looking for a reason to not go to the gym, we might have come up with the best one yet - they are not always good for the health. Gyms that have been built underground (Beijing is not short of these) often have poor ventilation and can become humid. This is a potential health risk and will counteract all those hard hours of exercise.

So before you sign up this spring in the desperate attempt to get in shape for the summer, read below and become a bit more in the know about where is good to sweat and where is not.

More wealth, better health

Although there are no official statistics for the number of gyms in town, according to the Beijing Municipal Bureau of Sports about 40 to 50 percent are built underground, taking advantage of lower rent and therefore the possibility to offer cheaper deals to attract more members.

He Yifeng, who has been working out in an underground gym for almost 10 months in the Central Business District, said he chose the gym mainly because it is close to his office and cheaper than other gyms. He got an 18 month membership for 1,800 yuan ($285), providing free access to the swimming pool, spinning classes, dancing and yoga courses. It is easy to see why he went for this option.

Similar gyms above ground can easily cost around 5,000 yuan upwards for the same length of time. But is it worth splashing out extra for the privilege of being upstairs?

"The main problems that might be caused by bad ventilation in underground gyms are respiratory diseases," said doctor Song Shifan, who works at Beijing's Huangshu Hospital of Traditional Chinese Medicine. "If the air gets stale the respiratory system is likely to suffer. Since the body is an organic whole, if you stay in that environment for a long time and get tired from excessive exercise, your immunity will become worse, thus causing more problems," warned the doctor.

People suffering from rheumatism, skin problems such as eczema and lung deficiency are also not advised to go to these places.

While women often prefer classes such as yoga and pilates, instructors warn the classes can cause more problems due to their emphasis on deep breathing. After a while in a confined space, you end up breathing in a lot of carbon dioxide, since the air will become turbid. "We all know that yoga requires people to take long, deep breaths. Therefore the ideal environment for yoga is one that has good ventilation," said Wang Yichi, a yoga instructor and founder of Uton Yoga in Beijing. "Without proper instructions, practitioners in such an environment distress their chest. If this continues over time, it could do severe damage to the body." Wang also added that if the place gets too humid, bacteria will be more prevalent.

If you insist…

If you do not have another option and have to go to an underground gym, there are a few factors to bear in mind when you choose the gym, said Li Abao, a personal trainer and consultant at Happy Fitness gym, an underground gym located in Chaoyang district.

As most gyms have central climate control systems, you don't need to worry about the temperature. However, given that basement gyms have worse ventilation, try to visit the gym during peak time to feel if the environment is comfortable. Ideally you want to make sure it is never too busy. A 3,000-square-meter gym sees an average of 300 users on a normal weekday, which is not a small figure, highlighted Li. Therefore if peak times feel unbearable, try to avoid going during these times. You do not want to fight for space, and air.

Also watch out for how crowded the gym is in terms of machinery. Ideally the treadmill and other equipment should be placed 1.5 meters apart, so that users do not have to breathe too closely to one another. For aerobic exercise, if the space is too crowded, it is important to increase the ventilation.