title: Physiological responses to diesel exhaust exposure are modified by cycling intensity.
abstract: BACKGROUND
  Outdoor exercisers are frequently exposed to diesel exhaust (DE) that contains particulate matter (PM) air pollution. How the respiratory and metabolic responses to exercise are affected by DE exposure and how these responses change with exercise intensity are unknown.
  
  
  OBJECTIVE
  This study aimed to determine the respiratory and metabolic responses to low- and high-intensity cycling with DE exposure containing high levels of PM.
  
  
  METHODS
  Eighteen males age 24.5 ± 6.2 yr performed 30-min trials of low-intensity (30% of power at V˙O2peak) and high-intensity (60% of power at V˙O2peak) cycling as well as rest. Each trial was performed once while breathing filtered air (FA) and once while breathing DE (300 μg·m of PM2.5) for a total of six trials, each separated by 7 d. During the trials, minute ventilation (V˙E), oxygen consumption (V˙O2), CO2 production (V˙CO2), RER, and perceived exertion for lungs (RPELungs) and legs (RPELegs) were measured. Work of breathing, respiratory muscle V˙O2, ratio of O2 consumption to power output, and gross efficiency were estimated.
  
  
  RESULTS
  The RER was significantly lower (0.02 lower, P = 0.008), and the RPELungs (0.9 greater, P = 0.001) and the RPELegs (0.6 greater, P = 0.017) were significantly greater, in DE compared with FA. During low-intensity exercise, V˙E (44.5 ± 8.9 vs 40.5 ± 8.0 L·min, P < 0.001), V˙O2 (27.9 ± 5.4 vs 24.9 ± 4.4 mL·kg·min, P = 0.001), and V˙CO2 (25.9 ± 5.3 vs 23.5 ± 4.5 mL·kg·min, P = 0.006) were significantly greater in DE. This pattern was not seen during high-intensity cycling.
  
  
  CONCLUSIONS
  Respiratory and metabolic responses to low-intensity, but not high-intensity, cycling in DE exceed FA. Practically, the greater responses during low-intensity exercise in DE could have implications for individuals with cardiopulmonary disease. Also, the elevated RPE during DE could impair performance in self-paced exercise.
authors.affiliation: 1School of Kinesiology, University of British Columbia, British Columbia, CANADA; 2Department of Kinesiology, University of the Fraser Valley, British Columbia, CANADA; 3Department of Medicine, University of British Columbia, British Columbia, CANADA; 4School of Population and Public Health, University of British Columbia, British Columbia, CANADA; and 5Division of Sports Medicine, University of British Columbia, British Columbia, CANADA.
authors.forename: Luisa V
authors.initials: LV
authors.lastname: Giles
authors.forename: Jason P
authors.initials: JP
authors.lastname: Brandenburg
authors.forename: Christopher
authors.initials: C
authors.lastname: Carlsten
authors.forename: Michael S
authors.initials: MS
authors.lastname: Koehle
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D006801:Humans; D019570:Inhalation Exposure; D008297:Male; D010101:Oxygen Consumption; D052638:Particulate Matter / Q000009:adverse effects; D005082:Physical Exertion / Q000502:physiology*; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D052638:Particulate Matter; D001335:Vehicle Emissions