Physical activity is important in preventing cardiovascular(心血管的) disease in young people so long as they don't undertake very intense activity on days when air pollution levels are high, according to a recently released study.
Until now, little has been known about the relationships between the health benefits of physical activity taking place outdoors and the potentially harmful effects of air pollution. Previous research by the authors of the current study had investigated the question in middle-aged people at a single point in time, but this is the first time that it has been investigated in young adults aged between 20—30 years over a period of several years. In addition, the researchers wanted to see what happens when people increase or decrease their physical activity over time.
At each health check-up, the participants completed a questionnaire asking about their physical activity in the past seven days and this information was changed into units of metabolic equivalent task(MET, 代谢当量任务) minutes per week(MET-mins/week). The participants were divided into four groups: 0, 1—499, 500—999 and 1000 or more MET-mins/week. People are recommended to do 500—999 MET-mins/week and this can be achieved by; for example, running, cycling or hiking for 15—30 minutes five times a week, or brisk walking, doubles tennis or slow cycling for 30—60 minutes five times a week.
The researchers used data to calculate annual average levels of air pollution, in particular the levels of small particulate matter that are less than or equal to 10 or 2. 5 microns in diameter, known a PM10 and PM25.
Overall, the results show that physical activity is associated with a lower risk of developing cardiovascular disease among young adults. However, when air pollution levels are high, exercising beyond the recommended amount may offset or even reverse the beneficial effects. The study cannot show that air pollution causes the increased cardiovascular risk, only that it is associated with it.
