Thought this was a good read.

Should You Exercise When You're Sick?
Training While Sick

By Hugo Rivera

Nothing can bring a bodybuilder's progress to a halt more than when you are sick. I am often asked the question, should I continue performing my bodybuilding training routines while I am sick? The answer to that question really depends on what you mean by sick. Is it a cold? The flu? Allergies? Most people confuse the common cold for the flu. However, these are different types of illnesses. The flu is caused by viruses known as Influenza A or Influenza B, while the common cold is caused by viruses called coronaviruses and rhinoviruses. There are over 200 different types of coronaviruses and rhinoviruses. If one of them hits you, your immune system builds a lifelong immunity to it (therefore, the same virus will never hit you twice). However, you have the rest of the viruses that have not yet affected you to worry about; and there are enough to last a lifetime.

The flu, as you may have already found out by experience, is much more severe as it is usually accompanied by an array of body aches and fever. Therefore, your body’s immune system is taxed much more by the flu than by the common cold. At this time, bodybuilding training would not only be detrimental to muscle growth, but it would also to your health as well. Remember that while training can help us gain muscle, lose fat, feel good and energetic, it is still a catabolic activity. The body needs to be in good health in order to go from the catabolic state caused by the exercise to an anabolic state of recuperation and muscle growth. So if you have the flu, your body is already fighting a catabolic state caused by the Influenza virus. In this case, weight training would only add more catabolism, which in turn would negatively affect the efficacy of the immune system against the virus, causing you to get sicker. Therefore, absolutely no training if you have the flu. Instead, concentrate on very good nutrition and on drinking large amounts of fluids (water and electrolyte replacement drinks like Gatorade in order to prevent dehydration). Once the flu completely runs its course, you can slowly start up back on your weight training program with lighter weights and not going to failure. Don’t push yourself too hard during this first week. The next week you’ll repeat what you did on the previous week again, but pushing yourself closer to muscular failure. By the third week of your program you should be back on track.

If it is the common cold that is hitting you and the particular virus is mild (you know that it is mild when your symptoms are just a runny nose and slight coughing), you may get away with training as long as you stop the sets short of reaching muscular failure and you decrease the weights poundages by 25 percent (divide the weights that you usually use by 4 and that will give you the amount of weight that you need to take off the bar) in order to prevent you from pushing too hard. Again, if the cold virus is causing you to feel run down, achy, with a sore throat and headaches, it would be best to stop training all together, until the symptoms subside. If this is the case, just follow the exercise program start-up recommendations described above for after the flu. Remember that we do not want to make it any harder for the immune system to fight the virus by introducing more catabolic activity, so intense training is out during that time.

If your ailment is something other than the common cold or the flu, consult your doctor.

Now that we have seen how a flu or a cold can throw a wrench into your progress, lets see how we can prevent these buggers from affecting us during the flu season or during any other season for that matter.

While it is still unknown why the cold and flu season generally comes during the winter months, it is known that you have to let the virus into your system in order for it to affect you. Therefore, it is only logical that we implement a two-fold prevention approach:

1. Prevent the virus from infiltrating your system. Keeping in mind that cold viruses spread by human contact, that they get into your system through the mouth, eyes and nose, and that they can remain active for up to three hours, you can accomplish this by doing the following:

* Keep your hands away from your face

* Wash your hands with anti bacterial soap frequently throughout the day (especially as soon as you finish your workout at the gym).

2. Maintain immune system operation at peak efficiency levels at all times. Remembering that excessive exercise, a bad diet, and losing sleep are all catabolic activities, do the following:

* Avoid overtraining by using the principles advocated in the Characteristics of Good Weight Training Routines article.

* Maintain a balanced diet as described in the Nutrition Basics article and avoid processed foods that contain high levels of saturated fats, refined flours or sugar since these types of foods lower the immune system function.

* Get a healthy dose of sleep a day (anywhere from 7 to 9 hours depending on your individual requirements).

So remember, stay healthy by following the tips above, and if you get sick, then “don’t beat a tired horse” as former Mr. Olympia Lee Haney used to say. Rest until you get better! If you don't you will end up more seriously ill and this will take you out of the gym for a longer period of time.

Good read, Dereck. This advice never gets old. Lee Haney also used one of my favorite phrases in relation to weight training:

"Stimulate, don't annihilate!"

I thought it pertinent especially during these times. I usually try to work through things hating to take days off but I have found in many cases this to work against me. Better to play it safe then sorry.

With our immune systems being protein based, this would definitely be depleted during our healing phase of being sick; hence why many people lose weight; that and lack of eating. But think if you added weight lifting that needs the proteins to rebuild the muscle; the immune system would be hit even harder in this state and you can guarantee you will just get more sick and take longer to recover.

I had been asked this before and just thought why not just read it from some experts.