Methodology: The current proposal is for a study of aerobic exercise in sedentary patients with poorly controlled asthma. In addition to usual care, 52 patients will undertake supervised aerobic exercise. The exercise program will consist of 3 X 1hr sessions of supervised exercise per week for 12 weeks. The exercise routine, under medical supervision, will consist of 10 minutes of warm up exercises, 40 minutes of biking and/or walking (and eventually jogging), and 10 minutes of cool down exercises. These patients will be compared to a group of 52 patients who will follow their usual regimen, this group will be offered the exercise programme once they have completed the post assessments. For the primary outcomes (asthma control [Asthma Control Questionnaire], quality of life [Asthma Quality of Life Questionnaire]) and secondary outcomes (inflammatory profile) will be evaluated at baseline and after 12 weeks (the length of the treatment). To check the efficacy of the intervention both lung function, ambulatory peak flow, and exercise tolerance data will also be collected. Repeated measures analysis of covariance-type models with time (pre, post intervention) as the within subject factor, group (exercise, usual care) as the between factor, and sex, age, and asthma severity as the covariates will be used for the primary outcome variables. To assess the potential mechanistic role of inflammation on the exercise-asthma relationship a series of regression-like GLMs will be conducted.