The dilemma of long-distance running enthusiasts—To run or not to run?
To run means facing air pollution on hazy days, where aerobic exercise draws more pollutants into the alveoli; not to run means a long-cultivated fitness habit is disrupted, leading not only to immediate weight gain but also a decline in future health metrics.
As a result, many opt to run in the gym. But is the air in the gym really safe?
Outdoor running can't beat smog and dust
On March 13, Xie Yan, Associate Research Professor at the Institute of Zoology, Chinese Academy of Sciences and overall coordinator of the Natural Conservation Legislation Research Group, joined several public welfare organizations in calling on the Beijing Municipal Education Commission to activate an “Air Pollution Day Emergency Plan for Outdoor Student Activities.” Reports indicated that most schools in Beijing responded to air pollution by stating they were “unaware of the recent severe air pollution” or “still awaiting clear municipal directives requiring the suspension of all sports activities during moderate to heavy air pollution.” Despite PM2.5 levels approaching 400, numerous schools continued outdoor activities such as morning runs, calisthenics, long-distance runs, and physical education classes.
In Shanghai’s general education system, even routine outdoor physical exercises are suspended due to the impact of smog. On January 8 and 16 this year, the Shanghai Education Supervision SMS Platform sent two air quality warning messages to principals and kindergarten directors of 3,053 primary, secondary, and preschool institutions across the city. The message on the 16th read: “Moderate to light pollution is expected during the day today. Susceptible groups such as those with heart disease or respiratory conditions are advised to reduce outdoor activities and physical exertion.” The Shanghai Municipal Education Commission stated that starting January 1 of this year, when the Shanghai Environmental Monitoring Center detects air quality conditions reaching or exceeding warning thresholds, warning information is promptly compiled and sent to the Shanghai Education Supervision SMS Platform via the Shanghai Education Supervision Affairs Center. Upon receiving the warnings, principals and kindergarten directors can adjust outdoor activity arrangements accordingly, ensuring these measures are implemented citywide.
According to research by Wang Yuesi, head of the Chinese Academy of Sciences’ “Atmospheric Haze Tracing” project team, smog contains large amounts of nitrogen-containing organic particulate matter that can cause immediate, chronic, and carcinogenic damage to the human body. Lung cancer mortality rates are highly correlated with haze particle concentration, making outdoor activities unsuitable for the public, let alone long-distance running. Data shows that lung cancer incidence in Beijing has risen by as much as 56% over the past decade, a trend Wang Yuesi believes is linked to outdoor running. He insists that primary and secondary schools should avoid organizing outdoor physical activities under severe air pollution.
Unlike the outdoor physical education classes of primary and secondary school students, outdoor activities for long-distance running enthusiasts are purely personal choices. “I usually run around 5:30 in the afternoon, and on weekends around 2 p.m.,” food writer Shao Wanshu told New Weekly. “Although there was a lot of smog this past winter, I still insisted on outdoor long-distance running. If the air is too bad, I go to the gym.” Of course, Shao Wanshu chooses indoor fitness venues with qualified air quality.
In Shanghai, there are no shortage of white-collar professionals like Shao Wanshu who are passionate about long-distance running. They gather online to form informal running groups. On New Year’s Day 2013, over 100,000 residents of Shanghai even participated in a welcome-the-new-year long-distance run. Yet at the same time, factors such as smog and air pollution have gradually made outdoor running a source of fear for enthusiasts. Especially with frequent incidents of running-related deaths—In October 2012, during the “2012 Hong Kong ITU Triathlon Asian Cup” held at Hong Kong Disneyland Resort by the Hong Kong Triathlon Association, a young lawyer-runner suddenly collapsed and died just steps from the finish line. Some doctors suggested his death may have been caused by air pollution triggering latent illnesses.
Then in November 2012, two participants died during the Guangzhou Marathon. On November 27, a third-year male student at Donghua University in Shanghai collapsed and died after completing a 1,000-meter physical test. Although the causes of death for these three individuals may not have been directly related to air pollution, the consensus is growing that “poor outdoor air quality leads to physical strain during running.”
Indoor running—more suffocating the more you run
As Shao Wanshu said, if the air quality is too poor, he chooses to run in the gym.
However, an investigation into multiple gyms in Nanjing found that many fitness venues lack a crucial air purification device: a fresh air system. Stale air is a common problem in these facilities.
Data released by China Fresh Air Network shows that an increase in the number of people and activity levels in gyms leads to a rise in indoor temperature. This environment encourages the proliferation of bacteria, viruses, and other microorganisms. In particular, the human body produces over 500 types of chemical substances during metabolism—such as sebaceous gland secretions, evaporated sweat, and shed cells carrying viruses, pathogens, and fungi. Exhaled human breath also contains over 10 toxic substances, including hydrogen sulfide, nitrogen oxides, and ammonia. Research indicates that after one and a half hours of exercise in a gym, the total number of bacteria increases significantly—by 15.5 times compared to levels before the gym opens.
A study by Associate Professor Lu Dajiang from the School of Exercise Science at Shanghai University of Sport showed that gyms often experience a buildup of carbon dioxide. A slight increase in inhaled CO₂ can stimulate the respiratory center, increasing breathing depth and rate, thereby boosting ventilation. However, when inhaled CO₂ exceeds a certain level, it accumulates in the body, inhibiting the central nervous system and respiratory movements, leading to symptoms of CO₂ narcosis such as difficulty breathing, headaches, and dizziness. As CO₂ levels rise, less oxygen is inhaled, stimulating chemoreceptors in the carotid and aortic bodies and reflexively increasing both breathing rate and heart rate, which raises blood pressure and leads to oxygen deprivation.
Another major source of air pollution in gyms comes from construction materials. Decoration-related pollution includes formaldehyde and various organic volatile compounds such as carbon monoxide, carbon dioxide, and airborne particles. Additionally, there is pollution from smoking, as well as electromagnetic radiation from computers, televisions, and mobile phones.
Exercising in a gym means no exposure to natural light, and improper use of air conditioning can easily lead to air-conditioning syndrome—making you feel more suffocated the more you run. Furthermore, dim lighting can cause fatigue, anxiety, and depression, while poor ventilation leads to stale air—all of which can negatively affect mental and behavioral health. Therefore, when exercising in a gym, it's essential to pay attention to the ventilation system. Ideally, choose a gym equipped with a fresh air system. Ventilation is a necessary measure to improve indoor environments. The direction of airflow can come from in front of, behind, the sides, above, or below the body. Heating air from below should be slightly cooler, while cooling air from above should be slightly warmer.