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Thursday, October 16, 2014

Fit Facts and Figures: How Exercise Improves Immune Function

How Exercise Improves Immune Function

The Immune System

For many of us, the immune system seems like a bit of a mystery. The immune system is large

and complex, and performs a wide variety of functions. Scientists and researchers are constantly

studying the immune system and making new discoveries.

Some of the factors that influence or affect the daily functioning of your immune system include

your age, gender, eating habits, medical status and fitness level.

Did you know that your skin is part of your immune system? Our skin is our first line of defense,

acting as a physical barrier to all the things in the world that can do harm to our body and make

us sick, such as bacteria and viruses.

White blood cells are another vital part of our immune system. There are many different types of

white blood cells that circulate throughout our body, playing different roles and all

communicating with one another.

A lesser known, but equally vital part of our immune system are hormones and cytokines.

Hormones and cytokines are important because they help cells communicate and help initiate

immune system defenses.

We don’t always think about it, but our immune system does a lot of great things every day to

keep us in good health. The immune system:

• Fights colds and flu viruses

• Deals with bacteria and viruses we may come in contact with

• Fights "bad" cells that form in our body (e.g., cells that could mutate and be cancerous)

Many Factors Influence Immunity

Your immune system is influenced by many things and will change throughout your life span.

Immune systems function differently for men and women, and vary from infancy to childhood,

and through adulthood. For pregnant women and older adults, changes to the system can be more

noticeable at times.

Your health can affect your immune system and vice versa. If you have a health condition, parts

of your immune system may not be working well enough or perhaps too well in some cases.

All aspects of our lifestyle can have an effect on our immune system, including the amount and

type of medications we may take for minor or major health conditions. Different aspects of our

lifestyles can also influence the immune system, including diet, stress levels and physical activity


SOURCE: Healthy U, Exercise and Our Immune System, Retrieved on March 4, 2014, from,

Can Exercise Help?

Battling another cough or cold? Feeling tired all the time? Taking a daily walk or following a
simple exercise routine a few times a week may help you feel better.

Exercise not only helps your immune system fight off simple bacterial and viral infections, it
decreases your chances of developing heart disease, osteoporosis, and cancer.

We don't know exactly how exercise increases your immunity to certain illnesses, but there are
several theories.

• Physical activity may help by flushing bacteria out from the lungs (thus decreasing the
chance of a cold, flu, or other airborne illness) and may flush out cancer-causing cells
(carcinogens) by increasing output of wastes, such as urine and sweat.

• Exercise sends antibodies and white blood cells (the body's defense cells) through the
body at a quicker rate. As these antibodies or white blood cells circulate more rapidly,
they could detect illnesses earlier than they might normally. The increased rate of
circulating blood may also trigger the release of hormones that "warn" immune cells of
intruding bacteria or viruses.

• The temporary rise in body temperature may prevent bacterial growth, allowing the body
to fight the infection more effectively. (This is similar to what happens when the body
has a fever.)

• Exercise slows down the release of stress-related hormones. Stress increases the chance
of illness.

SOURCE: National Institutes of Health, Exercise and Immunity, Retrieved on March 4, 2014, from,
Study Proves Exercise Boosts Immune System

The more physically fit and active you are, the less likely you are to suffer colds in the winter
months. That's the conclusion of US researchers, who studied about 1000 adults and found those
who exercised the most were least likely to suffer from colds in the winter months.

The researchers, from the Appalachian State University and the University of North Carolina,
have published their results online in the British Journal of Sports Medicine. They followed a
group of 1002 healthy adults aged from 18 to 85 years, over a 12 week period during the US
autumn and winter seasons in 2008.

At the beginning of the study, the subjects were examined, and questioned on their diet and
lifestyle, including how much exercise they did and how fit they perceived themselves to be.
Then, every day over 12 weeks, each participant reported any symptom of respiratory illness
they experienced (such as sneezes, coughs, fever or other symptoms) and its severity, according
to a standardized scale called the Wisconsin Upper Respiratory Symptom Survey.

Over the 12 weeks, the subjects reported experiencing symptoms of an upper respiratory tract
illness (URTI) on average for 13 days in the winter and 8 days in the autumn. But those who
were fit and exercised frequently were much less likely to develop a cold, and when they did, it
was much less severe.

Those in the top quarter for fitness levels (who did five or more days of exercise a week)
experienced 43 % fewer days with URTI symptoms than those in the lowest 25 % of fitness
levels (who did one day or less of exercise). And when they did get cold symptoms, the
symptoms were less severe. URTI symptoms were 32 % less severe in the top 25 % of exercisers
compared to the bottom 25 %.

(The researchers adjusted for various other factors that can affect immune response such as
mental stress, lack of sleep, poor nutrient status, and old age.)

Previous studies have also shown this relationship between fitness and reduced incidence and/or
severity of URTI symptoms, the researchers say. Exercise appears to reduce URTI incidence
anywhere from 18 to 67 per cent they say, depending on the study.

The precise nature of the link between exercise and increased immunity remains a mystery, but it
could be that each bout of exercise causes a transient increase in immune system activity,
increasing the numbers of white blood cells and immunoglobulin in the blood, which acts to
reduce a person’s susceptibility to disease the researchers suggest.

Associate Professor Stephen Turner from the Department of Microbiology & Immunology at
the University of Melbourne says he's not surprised at the findings. "As a general rule the
healthier you are, the easier you'll find it is to fight off infections", he says. “The effect may be

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", he says.
Although it's impossible for most people to avoid catching colds altogether, the findings do
suggest that regular exercise can reduce a person's chances of catching a cold, and/or reducing its
severity if they do catch it.

SOURCE: ABC Science, Study Proves Exercise Boosts Immune System, Retrieved on March 4, 2014, from,

Time to Get Moving

In general, it’s fair to say that research has shown that regular, moderate physical activity can be
beneficial to your immune system.

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 (e.g., watch
for signs of feeling worn out or cold/flu symptoms) and try to minimize other risk factors
for colds and viruses.

• Research has shown that consuming carbohydrates before a heavy training session may
help to ward off drastic immune changes, making you less susceptible to colds.

• Other research has shown that vitamin C may also help to ward off drastic immune

If you are feeling unwell, it may be best to delay your heavy training session until you are feeling

SOURCE: Healthy U, Exercise and Our Immune System, Retrieved on March 4, 2014, from,

For More Information

• Medline Plus – National Institutes of Health

• The President’s Challenge Program

Eric Dempsey
Master Sergeant, U.S. Army Retired
NASM Certified Personal Trainer and Weight Loss Specialist
Graduate Student in Exercise Science at Cal U.
Dempseys Resolution Fitness
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