In order to assess the relationship between the physical fitness of asthmatics and the clinical expression of the underlying disease, the authors studied 39 physically active children with moderate to severe but stable asthma. The patients (25 boys and 14 girls, aged between 9 and 16 years) were submitted to clinical evaluation; spirometry before and after bronchodilator (BD); maximal cardiopulmonary exercise test in cycle ergometer with breath-by-breath analysis of ventilatory and gas exchange variables; and, on a separate day, an exercise challenge test. As expected by the clinical stability, FEV1 post-BD was in the normal range in most of the children (mean ± SD = 93.8 ± 13.7% predicted). Maximal oxygen uptake (VO2max) was higher than the lower 95% confidence interval in 31/39 children; and in 29/39, the oxygen uptake at the anaerobic threshold (VO2AT) showed values above the lower limit of normality. Seven patients with low tolerance to exercise (reduced VO2max) presented suggestions of circulatory limitation (cardiovascular and/or peripheral) and only 1 had ventilatory limitation. There was no association or correlation between the lower ventilatory reserve (VEmax/MVV% ratio > 80%) and the decreased VO2max. Reduction in VO2AT, but not VO2max, was associated with some clinical indicators of asthma severity, e.g. (i) higher daily inhaled beclomethasone and frequent courses of oral steroids (p < 0.05) and (ii) higher exercise-induced bronchospasm occurrence (p < 0.01). The results show that (i) most patients with moderate to severe asthma, when clinically stable and physically active, present an adequate level of exercise tolerance; (ii) in estimation of the clinical severity of bronchial asthma in children, VO2AT is a better aerobic index than VO2max.

Keywords: Asthma in children. Exercise tolerance. Maximal oxygen uptake. Anaerobic threshold. Physical fitness. Exercise-induced