Shortness of breath on exertion is often due to lung problems, such as asthma, chronic bronchitis or emphysema, explains Healthline. Problems with the heart or blood vessels, such as congestive heart failure, dissection of the aorta or a condition known as "cor pulmonale," in which the right side of the heart doesn't pump blood effectively, sometimes cause shortness of breath as well. Less often, shortness of breath is the result of a blood clot in the lungs.
Asthma is a disease that causes inflammation of the small airways in the lungs, leading to wheezing, coughing and shortness of breath, reports Healthline. Inflammation also causes tightness in the chest muscles and excess mucus, both of which make it more difficult to breathe. Various substances trigger asthma symptoms, including pet dander, pollen, cigarette smoke and dust. In people who have exercise-induced asthma, symptoms appear only during or shortly after physical activity.
Doctors often refer to both chronic bronchitis and emphysema collectively as chronic obstructive pulmonary disease, explains the American Lung Association. This condition causes inflammation and gradual thickening of the air passages in the lungs and destruction of lung tissue, leading to poor oxygen exchange. As the disease progresses, the person becomes increasingly short of breath. Cigarette smoking is responsible for between 80 and 90 percent of all cases of COPD.
Heart problems often cause shortness of breath because the heart doesn't pump effectively, signaling the kidneys to hold on to fluid, which accumulates in the lungs, states WebMD. Known as congestive heart failure, this condition often causes shortness of breath on exertion as well as swelling in the arms, legs, ankles and feet.