First of all, see a doctor and take the appropriate medication to control exercise-induced asthma symptoms. Once the asthma is under control, you'll enjoy exercise much more. A flat stomach has more to do with what and how much you eat, than it has to do with exercise. If you have a fat layer around your middle, calorie reduction is the only way to lose the fat. Abdominal exercises can't hide or get rid of tummy fat.