The benefits of physical exercise are well known and we should all do a minimum of sports activity a week. In the current context of pandemic, and given the recommendations to avoid closed spaces, many people prefer to do sports outdoors: running, walking, cycling … However, and to complicate things, we also know that in situations of high air pollution, the risks of playing sports outdoors may outweigh the benefits. According to an article just published in the journal Environmental Research , air pollution caused by the burning of fossil fuels such as coal and oil was the cause of 8.7 million deaths worldwide in 2018.
When, then, should we avoid physical activity outdoors? A study recently published in the European Heart Journal tries to answer the question and concludes that physical activity is important to prevent heart and blood vessel disease in young people, as long as they do not do very strenuous activity on days when that air pollution levels are high.
The researchers followed more than 1.5 million young Koreans between the ages of 20 and 39 for several years, who were required to complete a questionnaire about their physical activity at each health check. This information was converted into ‘Metabolic Equivalent’ (MET-min), a unit with which the amount of energy – in calories – expended per minute of physical activity is established. The European Society of Cardiology recommends doing between 500 and 999 MET-min per week , something that can be accomplished by, for example, jogging, biking, or brisk walking for 15 to 30 minutes five days a week. Depending on the level of physical activity, the participants were divided into four groups: 0, 1-499, 500-999 and 1000 or more MET-minutes / week.
To obtain the data on air quality, they turned to the National Ambient Air Monitoring System in South Korea and classified the amount of exposure to air pollution into two levels: low to moderate (less than 49.92 and 26.43 micrograms). per cubic meter, μm / m3, for PM10 and PM2.5 respectively) and high (49.92 and 26.46 μm / m3 or more, respectively).
Lower cardiovascular risk
“We found that in young adults ages 20 to 39, the risk of cardiovascular disease, such as strokes and heart attacks, increased as the amount of physical activity decreased between the two screening periods in the low-level group. exposure to air pollution, ”explains Seong Rae Kim, first author of the article. “ However, in the group with high levels of exposure to air pollution, increasing the amount of physical activity to more than 1000 MET-min / week, which is more than the internationally recommended levels, could adversely affect cardiovascular health. This is an important finding that suggests that, unlike in middle-aged people over 40, excessive physical activity may not always be beneficial for cardiovascular health in younger adults when exposed to high concentrations of pollution from air”.
Air quality needs to be improved
Researchers conclude that it is imperative to improve the quality of the air we breathe in cities. “This way you can maximize the health benefits of exercise for young adults. These are people who tend to be more physically active than other age groups. Failure to improve air quality could result in an increased incidence of cardiovascular disease despite the health benefits of exercise. “
