What is more important, exercising or staying indoors during air quality warnings? – .

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What is more important, exercising or staying indoors during air quality warnings? – .


A haze of wildfire smoke hangs over downtown Calgary as a person climbs a flight of stairs on July 15, 2021.

Jeff McIntosh / The Canadian Press

On a family trip to Alberta last month, I got a taste of what millions of people across the country have faced this year. One day it was the sky of blue birds and the fresh mountain air; the next day it was so foggy we couldn’t even make out the steep peaks across the freeway from our hotel in Canmore.

This posed a dilemma for me and my wife. Our phones were ringing with warnings to stay indoors and avoid exercise due to the negative health effects of breathing smoke from wildfires. But we wanted to run.

There is no doubt that breathing polluted air is bad for your health, whether it is the small particles of seasonal smoke from forest fires or long-lasting irritants such as ground-level ozone and carbon monoxide. from cars and factories. In fact, you can use daily air quality readings to predict the increase and decrease in hospital admissions for conditions like strokes and heart attacks with remarkable accuracy.

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But there’s no question that exercise is right for you – and a recent study in the Journal of the Canadian Medical Association gives some cautious clues that the benefits of exercise, even in less than clean air, may. overcome the negative effects of air pollution. long-term.

The new study, led by Xiang Qian Lao of the Chinese University of Hong Kong, combed the medical records of 384,130 adults who signed up for a medical screening program from 1994. A questionnaire collected information on the subjects’ typical exercise habits, and their home address was used to estimate exposure to small particle air pollution.

As expected, those who exercised regularly had a lower risk of dying from natural causes during the study period. The most active third of subjects, who accumulated slightly more than the standard recommendation of 150 minutes of moderate exercise per week, reduced their risk by 35% compared to non-exercise.

When subjects were divided into three groups based on their exposure to pollution, the most polluted group had a 15% increased risk of death compared to the lowest group – also as expected.

The key point is the interaction between the two factors: intensive athletes (i.e. meeting or exceeding public health recommendations) in polluted neighborhoods lived longer than sedentary people and even moderate athletes in cleanest neighborhoods. The exercise clearly went beyond pollution.

The Lao study is not the first to come to this conclusion. A series of experiments conducted by Rodolfo de Paula Vieira, a researcher at Universidade Brasil, published in 2018, found that the anti-inflammatory and antioxidant effects of aerobic exercise appeared to exceed the lung inflammation and oxidative damage that would be otherwise produced by breathing polluted air.

Still, there are a few important caveats, Lao points out.

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“Our study targeted the combined health effects of ordinary exercise and chronic exposure to air pollution, ”he explained in an email. “This does not suggest that exercising for a short time with particularly poor air quality is a better option than not exercising, especially for vulnerable people. We recommend exercising indoors when the air quality is particularly poor.

The type of exercise can also matter. Research from the environmental physiology laboratory of athletic physician Michael Koehle at the University of British Columbia suggests that more intense exercise does not worsen the effects of pollution than light exercise. In contrast, the longest studies of exercise in pollution last only 90 minutes, so the effects of a four-hour bike ride, for example, are not studied.

“With such a long exposure to poor air quality, even if the intensity is low, the cumulative dose would be large,” Koehle said. This means that shorter and more vigorous may be a better option than long and slow during times of heavy pollution.

For Lao, the take-home message from his study is that people can benefit from regular exercise even if they live in a polluted area – an important finding, he says, because 90 percent of the world’s population lives in places where the air quality is not does not meet the guidelines of the World Health Organization.

There’s a bigger point, Koehle adds: Air pollution is bad all the time, not just during exercise. If you can work out early in the morning, in a traffic-free park, or in a gym with clean, reliable indoor air, this is a great idea. But you can (and should) also minimize your exposure for the other 23 hours of the day. If you can do it, then the data suggests that sneaking into a race on a smoky morning in Canmore – like my wife and I did – might not be so bad after all.

Alex Hutchinson is the author of Endure: mind, body, and the strangely elastic limits of human performance. Follow him on twitter @sweatscience.

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