The Truth About Exercise and Immune System Function

Exercise has endless health benefits, from heart-related to weight management, including reducing the risk of diseases such as diabetes.

Scientists have established an ‘inverse relationship’ between exercise and the risk of illness: an increased training frequency leads to a reduced risk of illness.

What is the immune system?

The immune system is a coordinated response of cell signalling between organs, a variety of immune cells and immune-related molecules, such as cytokines.

So, what is cell signalling? Well, put simply, cell signalling involves messages passing from one cell to another, often coordinated by cytokines. This process ensures that each cell is aware of risks and knows how to respond. The main aim of this well-managed response is to protect the body from harm.

Without the immune system, the body would not be able to fight pathogens that enter the body or identify changes occurring within the body. The key role of the immune system is:

  • To fight pathogens such as bacteria, viruses, fungi and parasites – and then remove them from the body.
  • To recognise the presence of harmful substances acquired from the environment and deactivate them.
  • Recognise and act on changes in the body that are harmful, including identifying cancer cells.

Foreign components entering our body activate an immune response. These components are called antigens and belong to pathogens such as bacteria.

When such a foreign body is recognised, the immune cells and immune molecules react together to fight the pathogen and remove it from the body.

When a particular pathogen infects us for the first time, we may feel unwell. However, information about the pathogen is stored – so in the event of a repeat attack, the immune system will respond quickly to identify and remove the pathogen. When the immune system is fully functional, you will not notice it; it is only when the system is weak or under attack from aggressive pathogens that you will feel unwell.

Running for Immune System Function

How does exercise affect the immune system?

A close link exists between exercise and our immune system. Exercising increases respiratory system activity, with our lungs working harder to draw in oxygen for delivery to the working muscles.

The increase in the depth and rate of the breathing may forcefully flush away any pathogens in the lungs, including bacteria and viruses.

Exercise has an effect on the immune system both during an exercise session and for a short period after. Studies show that moderate-intensity exercise (such as walking, jogging, or swimming for less than 60 mins) provides temporary changes to the response of essential cells in the immune system.

These moderate-intensity sessions kickstart essential cells and antibodies, encouraging them to move between the lymphatic system and the blood. Cells are now more likely to ‘bump into’ any foreign bodies that have gained entry to the host – you!

Although this effect is only temporary, over time, regular exercise leads to increased turnover of old cells to young cells and an improved ‘immunosurveillance’.

Immunosurveillance is like a patrol system: cells travel around our body looking for threats to identify, fight, and remove. Of importance are the natural killer cells and T cells, these are types of lymphocytes, also known as white blood cells (WBC) and are important for strong defences.

Can too much exercise negatively affect the immune system?

Exercise can positively and negatively affect the immune system. While regular exercise can undoubtedly enhance the immune system, prolonged periods of intense exercise can produce adverse effects.

Elite athletes are at an increased risk of infection (particularly upper respiratory tract infections – URTI), during periods of exercise stress. This is heightened around times of heavy training such as training for competitions.

It is believed that this is down to changes to immunity in specific sites, including the respiratory tract. Other crucial antibodies are reduced, which makes fighting infection more difficult, and hence, we become ill.

Also, excessive exercise may compromise the proteins necessary for proper immune function. We must ensure we’re getting enough protein to support the level of exercise we’re doing.

Carbohydrates are also crucial for exercise recovery and minimising immune system disturbances. A well-planned diet and exercise regime will ensure your immune system functions properly while aiding performance in your given sport.

Exercise and immune system myths

Myth: Too much exercise weakens the immune system

As we’ve discussed, exercise is good for the immune system; just don’t overdo it! Walk, jog, cycle whatever your preference, just keep your body moving.

Myth: Going out in the cold will make you sick

There is very little evidence to support the notion that cold weather will make you ill. People are more likely to stay indoors during cold weather which lead to an increased risk of catching a cold or the flu due to being in close proximity to others.

Myth: You can not exercise if you are sick

For the most part, you can still exercise when you’re feeling sick.

As you might expect, in some instances, it is not advisable – when suffering from respiratory tract infections, for example. However, many patients will exercise while sick to aid their recovery.

Cancer patients participate in light exercise during chemotherapy to improve strength, immunity, minimise fatigue, and improve mental health.

People with diabetes are encouraged to exercise to control blood sugar levels.

The common cold doesn’t usually present too many problems, although the intensity level may be moderated.

Either way, it is always important to check with a medical professional before participating in an exercise programme if unwell.

Final Words

Whether you’re elderly, obese, suffering from cancer or other diseases, or if you just have a common cold – exercise is an excellent way to improve overall immune function and health outcomes. This is of particular importance during these unprecedented times and the risk of COVID-19. However, it is important to understand that prolonged intense exercise can have a negative effect: striking the right balance is the trick here for maintaining a healthy and robust immune system.

Regular exercise and proper diet is the key to living a longer and disease-free life. So, whatever form of exercise you enjoy, we recommend you go and do it!

References

  1. Simpson, R.J., et al., Exercise and the Regulation of Immune Functions. Prog Mol Biol Transl Sci, 2015. 135: p. 355-80.
  2. Nieman, D.C. and L.M. Wentz, The compelling link between physical activity and the body’s defense system. Journal of Sport and Health Science, 2019. 8(3): p. 201-217.
  3. Peake, J.M., et al., Recovery of the immune system after exercise. J Appl Physiol (1985), 2017. 122(5): p. 1077-1087.

Dr Tracey Evans holds a PhD in Neuroscience, MSc in Molecular Neuroscience and BSc (Hons) in Biomedical Sciences. Working in medical research and as a scientific writer for Fitness Savvy, Dr Evans is passionate about health and mental well-being and has spent several years working as a fitness manager and personal trainer.

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