Friday, November 7, 2014

Is Exercising In The Haze Worth The Risk?

Hazy Singapore - Picture kindly allowed by Hak Liang from Flickr
I was away for the past 2 weeks and my parents when picking us up from the airport mentioned that the haze was bad over the weekend. However it's been raining a fair bit these past few days, so obviously no sign of any haze that has on occasion engulfed our skies in recent times.

When we exercise outdoors, we obviously breathe deeper and more frequently and hence take in more air pollution. A question often asked in times when the haze is bad is whether you should stop exercising outdoors to minimize exposure to the haze/ pollution.

The best known case I recall about an athlete worried about his health due to air pollution was Haile Gebreselasssie. He was then the world record holder in the marathon, but decided not to race the marathon at the Beijing 2008 Olympics due to concerns about the air quality as he suffered from asthma.

Now, there is much documented proof that regular exercise makes you smarter (a neurotropin - brain-deprived neurotropic factor, BDNF plays a key role).

There is also evidence that exposure to air pollution damages your brain and lungs.

Research suggests that while there may be benefits while exercising in polluted air, some of the positive cognitive effects of exercise may be lost. Consider the following two experiments.

A group of cyclists performed 2 identical cycling tests. One was done in a lab where the air was "clean" while the other test was done riding along a busy road with moderate pollution.

Result? Cylists' BDNF levels rose while performing the test in the lab. Along the busy road, levels did not.

In another study, subjects participated in a 12-week training program. One group trained in a rural environment, the other group an urban area. End result showed that participants in the rural environment performed better in tests involving working memory and problem solving.

The authors suggest exercising in a "green environment", avoiding close proximity to traffic, rush hour traffic, and polluted urban environments. Pollution tends to be less in rainy and windy conditions too.

So there you have it, some suggestions that the benefits you gain from exercise may be negated if the exercise was done in a polluted environment.


Bos I, De Boever P et al (2014). Physical Activity, Air Pollution And the Brain. Sports Medicine. 44(11): 1505-1518.

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