Smoke in the sky: Should I exercise or not?

This text was written by a TecMundo columnist; learn more at the end.

With air quality deteriorating in many Brazilian cities in recent weeks, the question arises: Should I exercise outdoors or could it be dangerous for my health? Science can help us understand this paradox: FExercise is good, but is it bad in polluted environments?

During physical exercise the body

During physical exercise, our bodies undergo physiological changes that can increase the effects of air pollutants on our health. For example, when running, we increase ventilation and the speed of inhaled air flow, and the passage of air through the mouth instead of the nose, which has air filtering mechanisms.

Such changes result in the transport of polluted air into the deepest part of our respiratory system, making it more dangerous.

Theoretically, high-intensity exercise could increase the risks even further, since it would intensify the changes described above. The question that science needs to answer is similar to whether it is better to walk or run to get less rain: Is it better to do light, prolonged physical activity when the air quality is poor, with more sun exposure in a polluted environment, or to do more intense, short-term physical activity?

Because of this scenario, attention is drawn to the possible contrast that can exist between exercising, which is a positive thing for health, and exercising in a polluted environment. something that may be harmful to health.

Although research shows that we spend most of the day (around 90 to 95%) exercising in homes, offices, schools, universities, hospitals and even gyms, indoor air quality is affected by outdoor air pollution. Exercise is also the time when some people choose to move outdoors and expose themselves to air pollution.

Understand pollutants

Air pollution consists of a complex mixture of particles and gases. The most studied pollutants include particulate matter (PM), ozone (O3), carbon monoxide (CO), nitrogen oxides (NO)._X) and sulfur oxides (SO_XEach has potential adverse effects on human health, but the target to be careful about in physical exercise is generally 2.5 or 10 µm (micrometer) particulate matter divided by size. The smaller it is, the greater its ability to penetrate the respiratory tract and the more dangerous it is for our health..

Exercising outdoors with polluted air: benefits or greater risks?

When researchers tried to answer the question of whether air pollution could cancel out the benefits of cycling or walking, they found that in the vast majority of cases, the benefits of physical activity far outweigh the risks of air pollution, given global average PM concentrations._2.5 in urban environment.

Only in areas with PM concentration_2.5 The risks of exercising above 100 µg/m³ would outweigh the benefits, but this is estimated to happen after just one and a half hours of cycling per day or more than 10 hours of walking per day. In 2016, when the study was published, cities with concentrations of such pollutants were mainly in China and India, but Brazil recorded concentrations at this level last week, which calls for caution.

Some cities in São Paulo have exceeded this level of pollution. While 10 hours of walking a day may seem like a lot, cycling for an hour and a half is a common activity and, according to research, may carry risks.

In a recently published study comparing air pollution exposure across seven modes of transportation, car, motorcycle and bus users were more exposed to pollutants such as CO and NO2 compared to active transportation (walking and running) users.

Those who walked or ran were more exposed to ultrafine particles, likely due to the proximity of vehicle emissions. Another study showed that despite greater exposure to pollution, people who moved actively gained an average of one year more life expectancy compared to motorized transport users.

Suggestions for your education

There is still a dilemma in advising people on exercise in relation to air pollution. It is accepted that air pollution deters people from doing physical activity because exposure to pollutants is associated with increased blood pressure, decreased lung function and increased respiratory symptoms, in addition to reduced capacity and performance in exercise. Therefore, it is recommended to take certain precautions:

• Monitor the conditions of the air where you want to exercise when data is available to minimize personal exposure to polluted air;
• The main platforms are: IQair and Air Quality Index (AQI), free platforms for monitoring weather conditions around the world. The truth is that Brazil is poor at monitoring air quality, meaning that in most cities we have no information about the air we breathe;
• Stay away from critical pollution points;
• Whenever possible, alternate the outdoor environment with the indoor environment, such as running on an indoor treadmill;
• In situations where exposure to polluted air cannot be avoided, such as a person commuting to work by bicycle, the use of masks (N95, KN95, FFP2) has been recommended due to their ability to filter small particles.

It seems that in general The benefits of exercise outweigh the risks of exercising in a polluted environment.Except where the contamination is severe and depends on the duration of exposure and the intensity of effort.

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Fabio Dominski He holds a PhD in Human Movement Sciences and a degree in Physical Education from the State University of Santa Catarina (UDESC). He is a university professor and researcher at the Laboratory of Sport and Exercise Psychology (LAPE/UDESC). He does scientific dissemination on social media and in podcast available on SpotifyAuthor of Physical Exercise and Science – Facts and Myths.