Rationale: Exercise is associated with improvements in asthma; however, the mechanisms responsible are not clear. Exercise induces changes in systemic inflammation, and it is possible that these inflammatory effects extend to the airways of people with asthma. Studies in healthy adults suggest inflammatory responses are dependent on exercise intensity: Although acute moderate exercise is antiinflammatory, acute vigorous exercise appears to be neutral or proinflammatory. The effect of exercise intensity on inflammation has not been investigated in people with asthma. Objectives: To compare acute changes in airway and systemic inflammation after a bout of moderate or vigorous exercise in physically inactive adults with asthma and to establish whether these effects differ according to asthma phenotype. Methods: Participants were randomized to either 1) control (no intervention), 2) 45 minutes of moderate exercise, or 3) 30 minutes of vigorous exercise. Induced sputum and blood samples were collected at baseline and 4 hours after intervention. Results: Fifty-six participants (75% female; mean age, 33.4 [9.9] yr) completed the trial. Moderate exercise induced a significant reduction in sputum eosinophil count (-173 [-337 to -10]; P = 0.032) and sputum percentage eosinophils (-2.2 [-4.9 to 0.5]; P = 0.049) relative to control. Vigorous exercise had no effect on airway inflammation. The antiinflammatory effects of moderate exercise were greatest in participants with eosinophilic asthma, with larger reductions in sputum eosinophils and larger increases in plasma interleukin (IL)-1ra than seen in participants with noneosinophilic asthma. Vigorous exercise induced a systemic proinflammatory response in participants with eosinophilic asthma, indicated by an increase in serum IL-5 and IL-1β; however, this had no effect on airway inflammation. Conclusions: Exercise intensity modifies the acute inflammatory response to exercise in adults with asthma. Although a bout of moderate exercise is associated with a reduction in eosinophilic airway inflammation, vigorous exercise has no effect on airway inflammation. Interestingly, the effects of moderate exercise vary by asthma phenotype, with greater antiinflammatory effects in participants with eosinophilic asthma. Future studies should examine the impact of exercise training at different intensities on inflammation and clinical asthma outcomes. Clinical trial registered with the Australian New Zealand Clinical Trials Registry (ACTRN 12615000294550).
Keywords: asthma; eosinophils; inflammation; moderate exercise; vigorous exercise.