In this issue of Thorax (see p 403), Shaaban and colleagues¹ report an inverse relationship between weekly exercise and bronchial hyperresponsiveness (BHR) in 5518 adults. Participants answered questionnaires on whether “they usually exercised so much that they got out of breath or sweaty” in order to estimate weekly frequency and duration of physical activity. Although this methodology may be difficult to validate, self-report questionnaires are used routinely to obtain information in epidemiological studies. These findings are consistent with the results of two previous studies: Rasmussen and coworkers² found that decreased physical fitness in childhood was significantly correlated with the development of adolescent asthma over a 10 year period, and Huovinen et al³ showed in a 17 year study of 262 twins that the …