Heavy exercise can provoke the onset of temporary lung problems and other symptoms typically associated with asthma in children who are not actually asthmatic, according to a new study by researchers at the University of California's Irvine and Miller Children's Hospital Children.
"Studies have shown that in adults, vigorous exercise can cause wheezing and a decrease in pulmonary function testing (PFT), even when there is no prior history of asthma. However, the extent of exercise-associated PFT abnormality in healthy children has received relatively less attention," said lead author and hospital clinician Alladdin Abosaida.
"The results of this study indicate that short bouts of heavy exercise do cause a decrease in lung function testing in healthy children without a history of asthma or allergies," he added.
Abosaida and colleagues examined the effects of exercise in 56 healthy children with no clinical history of asthma or allergy, measuring lung function following each exercise test.
"We evaluated two exercise protocols in each child - a constant work rate exercise test commonly used for evaluation of exercise-induced asthma, and a progressive exercise test typically used to determine an individual's aerobic capacity," Abosaida said.
Nearly half of the children tested had at least one abnormal result when pulmonary function was measured following exercise, he noted.
Decrements in PFT measurements typically occurred when bronchial tubes - the primary airways allowing air to enter and exit the lungs - become constricted in response to rigorous activity.
This effect, called bronchoconstriction, can arise as the result of an inflammatory response triggered by heavy exercise.
Abosaida said the results were surprising.
"We did not expect to see pulmonary function abnormalities after short periods of heavy exercise in such a large number of healthy children in our subject population. We speculate that either the inflammatory response to exercise or cellular changes that may occur as the result of dehydration of the airway surface, or both, led to mild airway obstruction," he said.
Additional research will need to be focused on determining the mechanism of lung dysfunction in children following heavy exercise, and may help identify potential interventions, Abosaida said.
The results of the study will be presented at the ATS 2010 International Conference in New Orleans.