Protective effects of repeated short sprints in exercise-induced asthma.

Many asthmatic patients demonstrate bronchial lability with a six-minute period of exercise, which is characterised by an initial bronchodilatation followed by bronchoconstriction. This early bronchodilatation response has been further analysed by investigation of the effects of repeated 30-second sprints before and after a six-minute run. It was found that these repeated short sprints did not induce bronchoconstriction, resulted in less bronchoconstriction after a subsequent six-minute run, and caused bronchodilatation if exercise-induced bronchoconstriction was present. It is postulated that this effect may be related to an increase in circulating catecholamines or altered vagal-sympathetic balance.