Asthma has increased in prevalence, morbidity and mortality over the past 20 years. Recent reports indicate that aerobic exercise improves the overall health of patients with respiratory diseases, including asthma; however, documented alterations in the asthmatic response as well as the mechanisms that underlie such alterations remain ill-defined. It is well appreciated that exercise profoundly influences the immune system; such effects include an exercise-mediated redistribution of T lymphocytes in vivo. Increasing evidence demonstrates that T lymphocytes play a central role in the pathogenesis of asthma. Exercise has also been reported to induce the release of endogenous glucocorticoids (GCs). Endogenous GCs act as anti-inflammatory agents through binding to the glucocorticoid receptor (GR) and subsequently altering transcriptional events. Based upon the preliminary data presented herein, the hypothesis of this proposal is that moderate intensity aerobic exercise attenuates the atopic asthmatic response via a mechanism that involves modulation of T cell responses and endogenous glucocorticoid-mediated actions. Proposed studies will: 1) Characterize the effect of aerobic exercise on inflammatory responses and pulmonary function within the atopic asthmatic lung; 2) Determine the effect of aerobic exercise on T cell responses within the atopic asthmatic lung; and 3) Delinate the role of endogenous GCs in the exercise-mediated attenuation of the atopic asthmatic response. Given that the increase in prevalence of asthma is a major public health concern, research that explores asthma-related therapies is vital. It is anticipated that this study will produce novel data regarding the therapeutic potential of aerobic exercise in the management of asthma.