It is a question that many ask themselves as they look out the window to the fresh morning haze over the Shanghai skyline: To exercise, or not to exercise?
As the full force of winter hits areas of northern China, the realities of factory activity and energy consumption are clear with pollution thickening the sky. Living with the realities of pollution can be frustrating, leaving many wondering about the impact pollutants like PM2.5, NOx, and O3 can have at high levels.
The facts are simple. These pollutants are damaging to your health, and on certain days, the effects can even be physically debilitating.
But what does this mean for your workout routine? Surely, when you exercise, your inhalation rate increases, forcing more dangerous pollutants into your body? Absolutely, yes, correct. However, to stop your thinking there discounts the positive physiological effects that exercise has on the body.
In a recent study conducted by University of Cambridge, researchers tested whether exercise effectively negated the negative impacts of air pollution on the body. In doing so, they used concentration of PM2.5, something well-known to any China resident, to measure pollution and assessed levels of exercise when resting, walking, and cycling.
Resting, walking and cycling? These seem like pretty generic terms, but in the paper, they are more specifically defined as ventilation rates of 0.61, 1.37, and 2.55 cubic meters of air per hour respectively.
Based on their measurements, “cycling” represents a ventilation rate increase at a factor of 4.18. Of course, this increase is specific to the individual, but it does give a good measure of the exercise intensity referred to in the study. The measurements and impacts are not addressed for higher levels of exercise intensity and ventilation rates, but we can assume that increasing one’s ventilation rate will increase potential harm from pollution intake.
So what does this all mean for a Shanghai resident? The graph below can provide some insight into the “tipping” and “breakeven” points for certain pollution environments when cycling. The “tipping point” refers to the point at which more exercise “doesn’t lead to higher positive health benefits”, and the “breakeven point” is the point at which “further exercise will cause adverse health benefits”.
Shanghai’s average PM2.5 concentration in 2015 stood at 52.9μg/m3, which is an Air Quality Index of around 149 (by US AQI). What the above graph tells us is that in polluted conditions like Shanghai’s, the most beneficial amount of time to exercise is around 80 – 90 minutes, though you will not start to suffer above average adverse health effects until you reach 300 minutes of cycling (at the stated ventilation rate).
Furthermore, the tipping and breakeven points shift based on the PM concentration for any city at any given time. See below:
It seems that in polluted conditions, some light exercise is better than none. Even in smog-filled cities like Shanghai, working out can still payoff in moderation. But don’t be fooled, positive health effects of physical exercise are higher in unpolluted conditions. When pollution is high, you should be careful with your exercise and continue to make the effort to protect yourself from the negative effects of air pollution as much as possible.
N.B. This study measured the impact of regular cycling/walking and long term (years) exposure to air pollution. Results might not fully represent the situation during high air pollution episodes.
To read our past articles about air pollution in China, check out our Landing Page and our Air Pollution Report. Follow Collective on social media to receive the latest updates, research, and announcements.