NEW YORK (Reuters Health) – Years of hard trainingmay be to blame for the higher-than-average rates of asthma thatare seen in elite swimmers, the results of a new study suggest.

The study, which compared teenage competitive swimmers withother adolescents, found that the young swimmers were no morelikely than their peers to have airway hypersensitivity andrespiratory symptoms suggestive of asthma.

The implication is that these problems in adult elite swimmersprobably arise after years of training, the researchers report inthe Journal of Allergy and Clinical Immunology.

High-level competitive swimming puts a high oxygen demand on thebody, leading to hyperpnea, or abnormally deep and rapid breathing.This, along with chronic exposure to environmental irritants aroundthe pool, such as chlorine, may lead to airway hyperresponsiveness– a hallmark of asthma in which the airways excessively constrictin response to an environmental trigger.