Effects of ambient particulate matter on aerobic exercise performance

Wintertime thermal inversions in narrow mountain valleys create a ceiling effect, increasing concentration of small particulate matter (PM_2.5). Despite potential health risks, many people continue to exercise outdoors in thermal inversions. This study measured the effects of ambient PM_2.5 exposure associated with a typical thermal inversion on exercise performance, pulmonary function, and biological markers of inflammation.

Healthy, active adults (5 males, 11 females) performed two cycle ergometer time trials outdoors in a counterbalanced design: 1) low ambient PM_2.5 concentrations (<12 μg/m³), and 2) an air quality index (AQI) ranking of "yellow." Variables of interest were exercise performance, exhaled nitric oxide (eNO), c-reactive protein (CRP), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV₁).

Despite a significant difference in mean PM_2.5 concentration of 9.3 ± 3.0 μg/m³ between trials (p < .001), there was no significant difference (p = .424) in the distance covered during low PM_2.5 conditions (9.9 ± 1.7 km) compared to high PM_2.5 conditions (10.1 ± 1.5 km). There were no clinically significant differences across time or between trials for eNO, CRP, FVC, or FEV₁. Additionally, there were no dose-response relationships (p > .05) for PM_2.5 concentration and the measured variables.

An acute bout of vigorous exercise during an AQI of "yellow" did not diminish exercise performance in healthy adults, nor did it have a negative effect on pulmonary function or biological health markers. These variables might not be sensitive to small changes from acute, mild PM_2.5 exposure.