<s>[INST] I am a runner and have been a runner for 7 years. For the past few months I have been having trouble with heavy legs, shortness of breath and lack of energy when trying to run. I feel lightheaded, have tunnel vision and am unable to get enough air into my body when I run. My family physician suspects anxiety. However, I have tried two different medications that have not helped. I have also seen a cardiologist who did a pulmonary function test, treadmill and tilt table test. All tests were negative. Do you have any other suggestions of what might be going on with me? My performance as a runner has declined substantially in the past few months. My times are getting slower instead of faster even though I continue to train as hard as I ever have. [/INST] Hello dear, thanks for your question on Chat Doctor. I can understand your situation and problem. Since your extensive pulmonary and cardiac work up is normal, no need to worry much for cardiac and pulmonary causes. Rare cause in your case is pulmonary embolism. Since all routine causes have been ruled out, get done CT pulmonary angiography to rule out Pulmonary embolism. If this is also normal, then no need to worry much. You are having mostly anxiety related symptoms. So better to consult psychiatrist and get done counselling sessions. Try to identify stressor in your life and start working on its solution. You may need newer anxiolytic Chat Doctor.  Avoid stress and tension. Be relax and calm. Don't worry, you will be alright. </s>