Exercise intolerance: deconditioning or cardiopulmonary dysfunction?

Case 65-year-old crossfit athlete

Reason for visit: Shortness of breath and lightheadedness during crossfit workout

How do we approach shortness of breath?

Shortness of breath and exercise intolerance can be due to many different causes. Some causes of exercise intolerance are cardiopulmonary disease, improper training, and diet. Physicians are trained to consider risk factors such as lifestyle, age, sex, smoking status, activity level, diet, and family history when evaluating a complaint of shortness of breath. They use this information along with other physical exam findings to come up with a list of possible causes known as a differential diagnosis and to determine what labs and imaging needs to be ordered.

Where do we start?

Cardiopulmonary disease can be a life-threatening cause of exercise intolerance. The lungs are responsible for oxygenating the blood and the heart is responsible for circulating blood throughout the body. A decrease in function of either one of these systems can decrease exercise tolerance. Age is a big factor when evaluating for cardiovascular disease. If you’re below the age of 30, inherited disorders such as hypertrophic cardiomyopathy should be ruled out. If you’re above the age of 35, it is important to evaluate for coronary artery disease. A wide array of testing is available to gauge cardiovascular and pulmonary function. Pulmonary function testing can assess how well the lungs are working. Stress EKGs can be used to evaluate the conduction system of the heart. Echocardiograms can be used to visualize the structure and function of the heart. Lipid panels and ASCVD risk are also used to determine risk and aid the formation of a heart-healthy plan.

After cardiopulmonary disease has been ruled out, what's next?

Diet and training habits can have a big impact on exercise tolerance. Performance can be negatively impacted if the body is not allowed to rest appropriately or is not properly fueled. Several tests and labs are available if it is suspected that improper training or dietary issues are responsible for the exercise intolerance. VO2 testing can be used to determine conditioning status. A sports medicine specialist should review the current training regimen and a custom plan can be formed to address recovery needs while still working towards long term goal. Micronutrient testing can be utilized to form a custom diet plan that addresses any dietary deficiencies.

So what should I do if I am experiencing exercise intolerance?

Call  Scottsdale Sport Medicine Institute to schedule an appointment with Dr. David Carfagno. Dr. David Carfagno is a Board Certified Internist and Sports Physician, who trained at the Cleveland Clinic Foundation. Our team can perform cardiovascular assessments, coordinate care between members of your healthcare team, perform fitness testing, customize nutrition plan along with other strategies that will help optimize your health and athletic performance.


Facc, B. (1996). Risk for Sudden Cardiac Death Associated With Marathon Running. Journal of the American College of Cardiology, 428-431.

Harmon, K., Drezner, J., Wilson, M., & Sharma, S. (2014). Incidence of sudden cardiac death in athletes: A state-of-the-art review. Heart, 1227-1234.