Immunology & Exercise

In the last 2 weeks I’ve had a lot of clients telling me they are ill, then telling me they are going to the gym to “work it off”.

Before doing this, ask yourself this question:

Am I really ill? or have I just got the sniffles and a cough every few hours? If so, you should just probably just take it steady and get on with your session.

BUT… if you are ill, and you care about your health and performance long term then you should think about the complications of training when your immune system is already depressed.

So here are the key players, there are many more players and many other roles but these are the popular cells in immunology… but I am not expert at this, its just a review.



T Cell = a type of lymphocyte (subtype of a white blood cell) and plays a central role in cell-mediated immunity. They multiply and differentiate into helper, regulatory or cytotoxic T cells or become memory cells. Once they are stimulated by the right antigen, helper T Cells secrete chemical messenger cells called cytokines, which stimulate the differentiation of B cells into plasma plasma cells (antibody producing). Cytotoxic T cells, activated by cytokines, bind too and kill infected cells – bosh.

NK Cell = a lymphocyte of the innate immune system that plays a major role in host-rejection of tumours and virally infected cell and they are cytotoxic. They serve to contain viral infections while the adaptive immune response is generating antigen-specific cytotoxic T cells that can clear the infection.

B Cells – with the help of T cells, they make T-shaped proteins called antibodies. Then the antibodies stick to antigens on the surface of germs, stopping them in their tracks and to create a build up that alerts the body to fight the infection.


Before going into this, training intensity needs to be taken into consideration… i.e. if you go for a casual walk in the park (which is classed as PA) it won’t affect your immune system as much as 60 minutes of strenuous resistance training. So a take home point, if you are feeling under the weather… opt. for low intensity steady state.

But if you are thinking about powering through the session after coughing your guts up all day, then be aware of how your body is going to respond to the stress of exercise and fighting an infection.

Exercise causes an increase in the numbers of circulating lymphocytes, specifically natural killer cells (NK cells) which is followed by a decrease in the number of cells during recovery from exercise. It appears to be because there is a decrease in the percentage of type 1 T cells and NK cells around at that time. A decrease T cell proliferation and T cell production is reported immediately after acute, intensive exercise. NK cytolytic activity doesn’t appear to change much after exercise unless the bout was prolonged, intense and stressful, in which it can depress the immune system for several hours after. Even for well trained athletes, intensified periods of training can result in a depression of immunity in a resting state. Research shows that is may be due to the effects of repeated bouts of intense exercise with the constant elevation of stress hormones, particular cortisol and anti-inflammatory cytokines causing a temporary inhibition of the type 1 T cell cytokine production.


So if you are really ill, stick to the basics…

1.) Rest / Recover / Sleep

2.) Drink plenty of water

3.) Eat a balanced healthy diet with high proteins, unrefined carbohydrates, healthy dose of fats and lots of fruit/ vegetables

4.) Ensure you are taking daily vitamins / mineral

5.) DO NOT – overdose on vitamin C thinking its going to cure you – it won’t.

6.) Start back with low intensity steady state

About The Author

Ben Hawksworth

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