Failing a sports physical can be caused by a variety of medical conditions. These include asthma, allergies, heart problems, diabetes, and other chronic illnesses. Asthma or allergies can cause difficulty breathing during exercise and may require the use of an inhaler to manage symptoms. Heart problems such as high blood pressure or irregular heartbeat can also lead to failing a sports physical. Diabetes requires careful monitoring of blood sugar levels before and after activity in order to prevent complications from developing during exercise. Lastly, any other chronic illness that could be exacerbated by physical activity should be discussed with your doctor prior to taking part in sports activities.