Should you exercise when you are sick? The answer is yes and no. If you have a common cold, you can exercise. If you have the flu, do not exercise.
A common cold is a virus that affects respiratory processes; nose, throat, lungs. Sneezing, coughing, headache, sore throat are common symptoms of the common cold. There are hundreds of cold viruses that lurk among. The total process of a cold lasts between 3 to 10 days. During the initial start of a cold the immune system is working hard to clear the body of the virus. At this time if you exercise, without overtraining, you can boost your immune system to help defend against the virus. However, if you overtrain you will weaken the immune system and allow the virus to become stronger in the system. This would cause the body to develop further problems in the respiratory tract; bronchitis, pneumonia, mononucleosis are some of the more severe conditions that can develop from a weakened immune system. If these conditions develop, exercising is absolutely out of the question. It is best to rest and take in the right amount of nutrients, and in some cases to take the appropriate medications or herbal remedies.
The flu on the other hand is horrible virus that is transmitted from person to person in the form of an airborne aerosol. Coughing, sneezing, chills, fever, sore throat, muscle pains, severe headaches, fatigue, irritability, general discomfort are all symptoms of the flu. There are many different strains of the flu virus. Most commonly the flu virus last between 24-48 hours. The more severe cases can last longer and can be life threatening. The flu is extremely dangerous for infants and older folks. The immune system of infants and older folks can't fight against the virus and this poses a health risk.
Once the symptoms of the flu develop it is not wise to try and exercise. Exercise will make the condition worse weakening the immune system even more. Once this happens then the virus really takes over and the symptoms get a much worse. Matter of fact I know this for a reason. I remember in college I started with the chills and aches and thought that if I exercised a little that I would feel better. Unfortunately, this didn't work, it made it worse. I was so sick that I had to go to the hospital to have an IV and heavy duty meds to boost my immune system. I had a typical flu virus but since I exercised I weakened my immune system beyond what it could do to defend against the virus. Ever since that experience I now pay attention to the signs and will lay off from exercise when I feel that the flu is coming on.
Getting sick is no fun and will play games with your ego. You might lose some weight and muscle while being sick, but that will all come back once you get to feeling better. It can get a little discouraging to see all of your hard earned efforts melting away when you are sick. But there are greener pastures ahead and once you get back on your feet you will be back in action and will start gaining again.