You’ve probably heard that physical activity is good for your health, but did you know that it’s great for your immunity too?
We often believe that vitamin supplements are the best way to boost our immunity. After all, the saying goes that an apple a day keeps the doctor away. But physical activity can also enhance our immune function.
This is essential for staving off disease and helping us remain healthy in today’s world, where we not only have to contend with fighting illnesses but also face lifestyle factors and environmental stressors that challenge our immune defences.
What is meant by ‘immune function’?
Our immune system helps us fight off pathogens (harmful invaders) that enter our body and would otherwise lead to the development of diseases and infections.
It consists of innate responses (those that are readily available) and adaptive responses (those that become engaged later on).
Our innate responses include things like our skin, which acts as a barrier to pathogens, and our leukocytes and natural killer cells (certain types of white blood cells) that are naturally present in our blood and help eliminate foreign bodies. Our innate immune system is what acts when we, for example, accidentally cut ourselves.
Our adaptive responses include T lymphocytes and B lymphocytes (other types of white blood cells) which develop to be pathogen-specific and directly target a particular foreign body once it invades. Our adaptive immunity is how we target new viruses we’ve never encountered before.
How can physical activity enhance our immune function?
Let’s explore in more detail how exercise contributes to these changes.
This happens in a number of ways. It:
- Boosts immune function. Exercise, even at moderate intensities, can increase the number of T lymphocytes, natural killer cells, and neutrophils in the immune system, as well as enhance their activity (Niemen et al., 2010).
- Improves circulation and immune cell mobilisation. When we exercise, blood is pumped around our bodies more rapidly, meaning there is also recirculation of our white blood cells (Niemen et al., 2010). This improved blood circulation helps the immune cells circulate through the body more efficiently, detecting potential pathogenic threats more rapidly.
- Stimulates the production of immune-boosting molecules. Exercise encourages the production of messenger-like molecules that stimulate other parts of the body. These include cytokines (like interleukin-10 or IL-10) and myokines (similar to cytokines but arising from muscle contractions, such as interleukin-6 or IL-6; Idorn & Straten, 2017). Antibodies are also released (Niemen et al., 2010), which bind to, inactivate, and destroy pathogens, supporting immune function (such as by launching an anti-inflammatory response).
- Reduces chronic inflammation. It is true that exercise acutely increases the inflammatory response around the body (it spikes) to respond to exercise-induced tissue damage. However, over time, exercise helps to regulate chronic low-grade inflammation (Simpson et al., 2020), which can be harmful in the long term (as it mediates many chronic diseases, such as cardiovascular disease and type II diabetes) and can weaken the immune system.
Research consistently shows that those who are regularly physically active are less likely to catch a cold and spend fewer days ill with an upper respiratory tract infection (e.g. Niemen et al., 2010; Chubak et al., 2010). Therefore, being physically fit and active may have cumulative benefits that lead to a more robust immune system over time.
Along with its physical benefits, exercise can improve psychological health, which in turn supports immune function.
Those who experience depression may be at increased risk of developing changes in immune function (Miller, 1998). Physical activity has been shown to have antidepressant properties, and this antidepressant action may reduce the chronic stress burden, which can benefit both brain and body health and resilience (McEwen, 2007; Lasselin et al., 2016). Indeed, mental health is closely tied to physical health, and exercise can play a key role in maintaining both.
Additionally, it has been found that exercise can attenuate the immunosuppression observed in subjects undergoing stress (Phillips et al., 2007). Effectively, stress suppresses immune function, but exercise has the potential to ameliorate the effects of this stress and support immune function.
This makes sense when we consider that many individuals find exercise to be a good stress reliever and incorporate it into their weekly routine for the psychological benefits it provides.
The fascinating thing about exercise and immune function – at least in my opinion.
So, we’ve established that exercise is beneficial for immune function, right?
That’s true, but it’s not always the case!
Have you ever wondered why so many athletes get sick and are unable to compete at the Olympics? By our previous logic, they train so much that their immunity should be superhuman!
Well, that’s not really the case.
It turns out there’s actually an inverse-U relationship between exercise and immune function.
When someone does no exercise, their immune function is likely to be quite poor. It tends to improve as one does more and more exercise… but only up to a certain point. After a period of prolonged or intense exercise (e.g. after a marathon), immune function actually begins to suffer! This is known as exercise-induced immune suppression.
It often results in upper respiratory tract infections in athletes. This happens because after a bout of intense exercise, the function of the body’s white blood cells changes and becomes impaired for a few hours (Moreira et al., 2009; Simpson et al., 2020).
Additionally, we see an increased level of cortisol with intense exercise, which also tends to suppress immune function (Smith et al., 1992).
This creates a window of ‘altered immunity’, within which one’s immunity is no longer in tip-top shape, and the individual is more susceptible to infections by invading viruses and bacteria (Hardman, 2023).
It may also be that there is decreased immunoglobulin or antibody secretion (most importantly immunoglobulin A or IgA) with prolonged intense exercise. These antibodies normally protect the mucosal surfaces (membranes that line the body’s cavities and organs that come in contact with the outside world) of the mouth and respiratory system, helping to protect the body against pathogens entering from here. If fewer immunoglobulins are secreted with prolonged exercise, this can also lead to an increased risk of upper respiratory tract infections (Hardman, 2023).
So how much exercise should we be doing to improve our immune function without pushing ourselves so hard that our immunity suffers?
There may not be any exercise training guidelines that are specific to immunity. However, the World Health Organisation’s weekly physical activity guidelines for adults suggest we should be doing at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity physical activity (or some combination of these), as well as two resistance training sessions a week.
Additionally, bouts of up to 60 minutes of moderate-to-vigorous-intensity exercise have shown benefits to immune function through the recirculation of white blood cells, cytokines, and antibodies around the body. Less than 60 minutes of moderate-intensity activity is also a short-enough exercise duration to avoid building up stress hormones and proinflammatory cytokines, which can suppress immune cell function (Niemen & Wentz, 2018).
Simpson et al. (2020) even state that there is consensus that short, 45-minute-long bouts of moderate-intensity exercise are beneficial for immunity, particularly in older adults and those with chronic diseases.
Therefore, doing about 30-60 minutes daily (or at least most days of the week) of moderate-intensity exercise, such as walking, cycling, or swimming, has the potential to boost our immunity without overloading our immune system or causing overexertion.
What steps can you take to improve your immune function today using exercise?
If you’re not doing any exercise right now, start small. Take the stairs every day or try walking or biking to work if your commute is not too long. Alternatively, you could join an exercise class or begin taking morning walks in the park. Maybe you’ve always wanted to take a Pilates class, and this could be the perfect excuse. Who wants to risk getting ill more often?!
The truth is, if you’re not physically active right now, adding any form of exercise to your weekly schedule can be beneficial! Try not to view it as a giant 1-hour daily commitment.
If you gradually start exercising twice a week, you may soon find that you actually enjoy it and look forward to your daily exercise session.
To complement your exercise, you might want to think about eating a healthy balanced diet, getting enough sleep, and making sure you’re well-hydrated. All these factors together will work to boost your immunity and help keep you infection-free!
Conclusion and Call to Action
So, it appears that after an acute bout of vigorous-intensity exercise, there is a window during which one is more susceptible to illness (Pedersen & Hoffman-Goetz, 2000). However, over the long term, those who engage in moderate-intensity physical activity tend to have a lower likelihood of infection and increased circulation of immune cells around the body (Pedersen & Hoffman-Goetz, 2000).
Therefore, it seems that doing around 45 minutes of moderate-intensity physical activity daily can be extremely beneficial for your immunity, even if you’re older or suffer from a chronic disease (Simpson et al., 2020)!
So, try finding a form of exercise you enjoy and take small steps to incorporate this kind of physical activity into your routine.
If you don’t know where to start, you can try a 30-minute-30-day walk challenge. For a month, try setting aside just 30 minutes of your day to go out for a walk. You can choose to wake up earlier to fit it into your schedule, or use it to unwind at the end of your day before going to bed. You can even use it as a good excuse to get some air during your lunch break!
Whichever way works best for you, just give it a try. You might just come to cherish your walking time and appreciate the short spell of peace and reflection it provides. If nothing else, it will certainly be great for your mental wellbeing.
References
Chubak, J., McTiernan, A., Sorensen, B., Wener, M. H., Yasui, Y., Velasquez, M., Wood, B., Rajan, K. B., Wetmore, C. M., Potter, J. D., & Ulrich, C. M. (2006). Moderate-Intensity Exercise Reduces the Incidence of Colds Among Postmenopausal Women. The American Journal of Medicine, 119(11), 937-942.e5. https://doi.org/10.1016/j.amjmed.2006.06.033
Idorn, M., & Straten, P. T. (2017). Exercise and cancer: from “healthy” to “therapeutic”?. Cancer Immunology, Immunotherapy : CII, 66(5), 667–671. https://doi.org/10.1007/s00262-017-1985-z
Lasselin, J., Alvarez-Salas, E., & Grigoleit, J.-S. (2016). Well-being and immune response: a multi-system perspective. Current Opinion in Pharmacology, 29, 34–41. https://doi.org/10.1016/j.coph.2016.05.003
McEwen, B. S. (2007). Physiology and Neurobiology of Stress and Adaptation: Central Role of the Brain. Physiological Reviews, 87(3), 873–904. https://doi.org/10.1152/physrev.00041.2006
Miller, A. H. (1998). NEUROENDOCRINE AND IMMUNE SYSTEM INTERACTIONS IN STRESS AND DEPRESSION. Psychiatric Clinics of North America, 21(2), 443–463. https://doi.org/10.1016/s0193-953x(05)70015-0
Moreira, A., Delgado, L., Moreira, P., & Haahtela, T. (2009). Does exercise increase the risk of upper respiratory tract infections? British Medical Bulletin, 90(1), 111–131. https://doi.org/10.1093/bmb/ldp010
Nieman, D. C., Henson, D. A., Austin, M. D., & Sha, W. (2010). Upper respiratory tract infection is reduced in physically fit and active adults. British Journal of Sports Medicine, 45(12), 987–992. https://doi.org/10.1136/bjsm.2010.077875
Nieman, D. C., & Wentz, L. M. (2019). The compelling link between physical activity and the body’s defense system. Journal of Sport and Health Science, 8(3), 201–217. https://doi.org/10.1016/j.jshs.2018.09.009
Pedersen, B. K., & Hoffman-Goetz, L. (2000). Exercise and the Immune System: Regulation, Integration, and Adaptation. Physiological Reviews, 80(3), 1055–1081. https://doi.org/10.1152/physrev.2000.80.3.1055
Phillips, A. C., Burns, V. E., & Lord, J. M. (2007). Stress and Exercise. Exercise and Sport Sciences Reviews, 35(1), 35–39. https://doi.org/10.1097/jes.0b013e31802d7008
Smith, J. A., McKenzie, S. J., Telford, R. D., & Weidemann, M. J. (2019). Why Does Moderate Exercise Enhance, But Intense Training Depress, Immunity ? CRC Press EBooks, 155–168. https://doi.org/10.1201/9780429260445-17
World Health Organization. (2020). WHO Guidelines on Physical Activity and Sedentary Behaviour. https://iris.who.int/bitstream/handle/10665/336656/9789240015128-eng.pdf?sequence=1