how exercise affects the immune system

The flu season is almost upon us. So what can we do to boost our immune system to prevent colds and flu? And if you have a cold or flu, can you exercise? These questions will be answered in this article, but first, let’s take a look at what exactly is the immune system.

What is the immune system?

Lymph nodes:
Lymph nodes are part of your lymphatic system. The lymphatic system produces and store cells that fight infection and disease. It also produces and stores a clear fluid, calledlymph that carries those cells to different parts of the body. Lymph nodes filter the lymph fluid and store cells that can trap bacteria or viruses travelling through the body in the lymph fluid. 

Thymus:
The Thymus is a small organ just behind your breastbone. This is where theT-cells mature (the reason why they are called T-cells is because they mature in the Thymus)

Spleen:
The spleen is the largest lymphatic organ in the body. It contains white blood cells that fight infection or disease. The spleen also helps regulate the amount of blood in the body and destroys old and damaged blood cells.

Bone Marrow:
This is yellow tissue in the centre of the bones that is responsible for making white blood cells that will eventually form lymphocytes.

Lymphocytes:
These aresmall white blood cells that play a large role in defending the body against disease. There are two main types of lymphocytes: B-cells and T-cells. B-cells make antibodies that attack bacteria and toxins and T-cells help destroy infected cells.

The Immune System in Action

When a virus enters the body, the following processes will activate:

The body recognizes a foreign antigen(virus or bacteria) and sends it to the lymph system, where it is taken up by a macrophage (cells of the immune system.The macrophage processes the virus and “writes” a code for that virus on the outside of the macrophage.

The antigen signals a helper T- cell. The T-cell reads this signal and signals the other parts of your immune system.

B-cell responds to the signal and reads the antigen from the outside of the macrophage.The B-cell becomes activated and produces antibodiesspecific to the antigen. These antibodies are released into your body to attach to the virus.

The antibodies attach to the antigens. The antibodies send a signal to other macrophages and other immune cellsso that they can surround and destroy the antibody.

Once the number of antigens has dropped and the infection has resolved,suppressor T-cells (cells that inhibit, suppress, or help to stop an immune response) will signal the other cells of the immune system to rest. 

Exercise and the immune system
How can exercise boost the immune system?

There are a lot of factors that influence the immune system. Some of these factors include your age, gender, eating habits, medical status and fitness level.

It has been shown that regular, moderate-intensity physical activity can help protect the body against some diseases, especially those that involve the upper respiratory track (like colds).

Early studies found that recreational exercisers stated that they experienced fewer colds once they began exercising regularly. More recent studies have shown that there are actual physiological changes that occur in the immune system as a response to exercise:
·         Moderate exercise has been linked to a positive immune system response and a temporary boost in the production of macrophages (the cells that attack viruses and bacteria).
·         During moderate, continuous exercise, your heart gets stronger which allows it to pump more blood throughout the body.
·         During moderate, continuous exercise, the lungs get better equipped at handling oxygen and distributing it to the rest of the body. The lungs will also be better equipped to flush viruses and bacteria out of the lungs.
·         During moderate exercise immune cells circulate through the body at a faster rate and are better able to kill bacteria and viruses.
·         Researchers have found that moderate, continuous exercise produces a blunted immune system stress response. This indicates the immune system has adapted to regular exercise and can tolerate this kind of stress much better. Just like muscles adapt to exercise over time, so does the immune system.
·       During moderate exercise, the temporary rise in body temperature may prevent bacterial growth, allowing the body to fight the infection more effectively. 

After exercise ends, the immune system generally returns to normal within a few hours, but consistent, regular exercise seems to make these changes a bit more long-lasting. Therefore, when moderate exercise is repeated on a near-daily basis there is a cumulative effect that leads to a positive long-term immune response. This will also allow the body’s immune system to ward off heart disease, type 2 diabetes, osteoporosis, and some kinds of cancer.

How can exercise harm the immune system?

As in so many things in life, moderation seems to rule the day. If you don't exercise enough, it's not healthy; if you exercise too much, it’s not healthy either. Pushing yourself too hard during exercise does not make much sense when you think about how the body reacts to exercise. When the body is in a state of exercise it is a kind of stress to which the body must adapt. In doing so, the body leans on the immune system. Later, when, and if, the body has had a chance to rest and marshal its forces, it will be much stronger going forward. But if the body never gets enough rest, or when another form of stress hits, it can't mount an effective defence.

Studies show that too much intense exercise can reduce immunity. Research is showing that more than 90 minutes of high-intensity endurance exercise can make athletes susceptible to illness for up to 72 hours after the exercise session. Intense exercise seems to cause a temporary decrease in immune system function. During intense physical exertion, the body produces certain hormones that temporarily lower immunity. Cortisol and adrenaline, known as the stress hormones, raise blood pressure and cholesterol levels and suppress the immune system. This effect has been linked to the increased susceptibility to infection in endurance athletes after extreme, high intensity, prolonged exercise. 

Can you exercise while you are sick?

It is typically safe to exercise at a low intensity if you have "above-the-neck" symptoms (runny nose, sneezing, sore throat). If those symptoms diminish during the first few minutes of exercise, the intensity may be increased. Exercise isn't recommended for people with "below-the-neck" symptoms (fever, sore muscles or joints, vomiting, diarrhoea, or a cough that produces mucous). If you have those symptoms, let the cold run its course before you resume physical activity.

Take-home message

Exercising at a moderate intensity at least 40 minutes per day helps the body resist a variety of diseases and conditions. High-intensity endurance activities that last 90 minutes or longer may increase your susceptibility to infection for up to three days. As with diet and other health-related behaviors, a program of exercise that consistently and progressively challenges the systems of the body without severely compromising them is the most sensible training strategy.

 The important factors when exercising are:
·         Knowing how much exercise is enough
·         When exercise is appropriate and when it's not
·         Which types of exercise are appropriate for your particular situation

If you are just beginning to exercise more often, here are some tips:
·         Take your time. Your immune system and the rest of your body will need time to adapt to regular exercise.
·         Start at a duration and intensity level you can easily manage. For some that may be 30 minutes, for others, it may be 10 minutes.
·         Keep in mind that positive changes in your immune system are just one small additional benefit you will get from regular exercise. There are many other health benefits as well, such as improved cardiovascular fitness and endurance, and improved flexibility, muscle strength and balance.

For people who exercise regularly, here are a few pointers:
·         Light and moderate exercise won’t be harmful, and in some cases may make you feel better when you are feeling a little under the weather.
·         It’s okay to have a heavy workout, but it’s not necessary to do a heavy workout every day. Your body and immune system need a chance to rest and return to a normal state.

For athletes and those who train hard (at high intensity levels):
·         When you are following a heavy training regime, keep an eye on your health. Watch for signs of feeling worn out or any cold/flu symptoms and try to minimize other risk factors for colds and viruses.

The more physically fit and active you are, the less likely you are to suffer colds in the winter months. As a general rule the healthier you are, the easier you'll find it is to fight off infections. We know that people who exercise regularly have lower levels of stress hormones in the blood, and there's a definite link between low levels of stress hormones and improved immunity. Although it's impossible for most people to avoid catching colds altogether, the findings so suggest that regular exercise can reduce a person's chances of catching a cold, and/or reducing its severity if they do catch it.

just for laughs:

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