Peak expiratory flow rates before and after exercise in schoolchildren

Peak expiratory flow rates (PEFR) were measured before and after 6 minutes' exercise in 12-year-old schoolchildren living in two areas. In boys, but not in girls, the mean initial PEFR was lower in asthmatics than in nonasthmatics. After exercise, children with current asthma tended to show a marked fall in PEFR. Children with a history of wheezing, atopic disease, or a first-degree asthmatic relative showed something of the same tendency, though their responses to exercise largely overlapped those of the control group. The unknown mechanism causing exercise-induced asthma appears to operate also in some subjects who show features related to asthma, but not in the rest of the child population