To get the answer, I consulted Dr. Barry Goldman, director of my Center for Performance Enhancement and Lifestyle Management at Ochsner Clinic Foundation. Goldman's answer to this question is a very succinct "No." One of the major medical concerns, he says, is the potential for dehydration. If someone is already running a fever, he or she runs the risk of aggravating that fever by dehydrating during or after a strenuous workout.
The increased action of physical activity on the body and its functions has the effect of raising the body's temperature. This decreases its ability to fight infection-causing microorganisms, especially in the upper respiratory region. Leucocytes or white corpuscles are the body's primary defense against invading germs and infectious bacteria. They do their best work when the body is engaged in little or no strenuous activity. When the body is at rest, the leucocytes can focus on performing the function they were designed to perform, attacking and neutralizing the microscopic alien forces that make us ill.
"If you're sick, listen to your body," Goldman advises. "Working out while you're ill can do much harm with little gain. Take the time off to heal your body. Get the appropriate medical treatment and always listen to your doctor's advice."
Some illness-causing viruses can worsen in the chest area and lower extremities if they are aggravated by intense physical activity while you are sick or recovering from an illness. For example, myocarditis could result. This is a disease that negatively impacts the body's natural immune system, resulting in a negative nitrogen balance and muscle protein degradation. Whereas moderate physical training actually stimulates the immune system, exhaustive and strenuous exercise may be followed by a temporary immunodeficiency. This can lead to an increased susceptibility to respiratory tract infections. Exercising in the acute phase of an infection may promote ailments like myocarditis.
So, the best advice I can offer as to whether or not you should work out when you're sick is the same thing Dr. Goldman emphasized. Consult your physician and listen to your own body. Don't take chances with your physical health and well-being; don't push yourself. Just as your body needs physical stimulation to stay in proper shape, it also needs respite from exertion when it's not quite up to peak operating efficiency. If you're sick, give yourself a break from your regimen. Take vitamins, supplements and medicines that promote physical recovery only under your doctor's supervision. Eat healthy meals that are rich in essential nutrients. A licensed nutritionist can advise you on a proper meal plan. Allow your body the time it needs to recover, give it the rest it is demanding and, in due time, you'll be well and back into your normal exercise routine again.