How Does Exercise Boost My Immune System?

I first came across this subject matter when studying immunology when completing my Masters Degree in Sport Science and found it very interesting! In fact, despite the title of this blog, exercise can work both ways in regards to fending off those colds and upper respiratory tract infections (sore throats) and can actually lower your immune system (1). Let’s go through some of the literature!


Steady state exercise between 30-50% of maximum heart rate for 20 minutes can actually boost your immune system (1). This can be anything from walking, slow jogging or even cycling. It has been found that we have something called “natural killer cells” within us that increase after the event and help fight off pathogens that try and invade our healthy cells.

So if you are down in the dumps get off the couch and get a brief spell of low intensity physical exercise in you!

On the other hand you will want to stay away from experiencing “over training syndrome”, difficult to study as it is unethical to put subjects directly into this state for health reasons. However, some studies have been done to lesser severity. A Swedish study analysed over 1000 marathon runners and found that the competitors that where considered “untrained” experienced a sore throat two weeks after the race while the “trained” did not.  

Now a lot of variables could have caused this but most of the untrained runners experienced this. They concluded that the event was far too robust for them and their immune system paid the price for it as their white blood cell count was lower than base line measures (1).

Apparently men may have a stronger immune response to exercise to woman as well? Or as this particular study put it a higher “immunosurveillance” suggesting a lower risk to infection to short bursts of 7x200m of front crawl in athletic swimmers. Again white blood cell count was slightly lower after the exercise protocol. Again variables such as nutritional status, quality of the water in the pool, current stress levels and previous infections may have altered these results.

It’s vitally important to ease your way into exercise if it is brand new to you so the body can adjust in its own time to the new stimulus thrown in its way. If you go too fast too soon this is when you invite problems in regards to your immune system. A carefully planned periodized exercise programme will ensure you do not get sick (coupled with excellent nutrition of course).

This slow increase of the over load principle of training will ensure you adapt accordingly. Listen to your body in response to physical training, if you feel lethargic, loss of concentration, experience poor sleep, constantly have aching muscles and lack of drive to train, you are probably teasing the over training syndrome. Rest days are as vitally important to your training days.

To conclude, try not to over do it in regards to exercise, athletes are highly trained individuals and took years to achieve what they have physically and mentally. A couch potato will need careful integration and planning of exercise to hit and achieve their goals in regards to health. Nutrition plays a massive role in our immune systems (another blog on another day!), just help yourself and avoid processed packaged foods and select organic whole foods that are nutrient dense. A top Personal Trainer will help you with all of this! 

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(1) Pedersen et al (2000), Exercise and the immune system: Regulation, Integration and Adaptation, Physiological reveiws, vol 80, no3.