A single bout of moderate exercise can reduce airway inflammation in people with asthma, according to Australian research.

A study, published in the Annals of the American Thoracic Society, randomised 56 inactive adults with asthma to either no exercise, 45 mins moderate exercise or 30 mins vigorous exercise.

The study found moderate exercise led to significant decrease in sputum eosinophil count (p=0.032] and sputum % eosinophils (p=0.049] four hours following moderate exercise relative to controls.

Meanwhile, there was no effect of vigorous exercise on sputum eosinophil count or sputum % eosinophils relative to control. There was also no effect of either intensity of exercise on sputum neutrophils or FeNO.

Both moderate and vigorous exercise induced an increase in serum IL-6 and blood neutrophils relative to control. There was also an increase in plasma IL-1ra following moderate, but not vigorous, exercise relative to control.

“We also observed a significant interaction between exercise intensity and asthma phenotype, whereby moderate exercise reduced eosinophilic airway inflammation in participants with eosinophilic asthma (EA) but not in participants with non-eosinophilic asthma (NEA),” the researchers said.

“There was no effect of vigorous exercise on sputum eosinophils in participants with either asthma phenotype, suggesting reductions in eosinophilic airway inflammation were specific to participants with EA undertaking exercise of a moderate intensity.”

Led by the University of Newcastle’s Dr Hayley Scott and with senior investigator Professor John Upham from the University of Queensland’s Diamantina Institute, the researchers said there was also a significant interaction between exercise intensity and asthma phenotype on circulating IL-1β and IL-5 in participants with EA.

“This is the first study internationally to examine the impact of exercise intensity on inflammation in adults with asthma,” they said.

“We found that, while moderate exercise was associated with a reduction in sputum eosinophils, vigorous exercise had no effect. This finding is supported by studies in healthy adults, which show that moderate exercise elicits anti-inflammatory effects in the bloodstream, while strenuous exercise can have either neutral or pro-inflammatory effects.”

“Future studies should investigate the impact of exercise training at different intensities on inflammation and clinical asthma outcomes,” they added.

Professor Upham said future research could also help boost public health messaging around exercise and asthma. Fears of exercise triggering asthma attacks prevents some sufferers from being active, and COVID-19 has increased their concerns.

“We hope with future research we can develop some tailored advice to help people with asthma take a healthy approach to exercise,” he said.