We know exercise is important…and we know building a strong immune system is, too. But could one help the other? Heather Huntsman, Ph.D., CSCS digs into the science behind the connection between physical activity and immune system health – perhaps a new source of motivation to get you moving!
By now, you may know the link between exercise and immunity, especially if you’re in the business of optimizing health. However, let’s take it a step further and dig deeper into how exercise and the immune system are connected.
First, it is important to understand the primary function of the immune system. Simply put, the immune system’s number one responsibility is to protect the body by recognizing any and every outside invader and either keep it from getting inside your body, or to destroy and eliminate anything that manages to make its way in. It has several strategies for doing this, from physical barriers like the skin and mucous membranes, to specialized cells, collectively referred to as white blood cells, that act like little soldiers marching throughout your body to identify and kill bacteria, viruses, and any other foreign body.
Then there is exercise. When we break it down to its most basic parts, exercise is simply a stressor that we place on the body to cause adaptation. When we increase our heart rate, it strengthens the heart muscle which increases the amount of blood it can pump per beat and ultimately improves circulation. When we lift heavy things, our muscles grow so the next time we lift that same heavy thing, it isn’t as hard. These are just two very simple examples to prove my point, but in reality, I could go through just about every tissue or organ in the body and describe how exercise stresses it (in a good way!) and the resulting adaptation. Exercise really is medicine that has huge benefits for every system in our body.
So, what about the immune system? How does exercise improve immune system function? The answer to this is actually fascinating. Because the immune system is just that, a system, rather than one localized organ, it directly and indirectly benefits from several exercise-induced adaptions that all result in improved immunity.
As stated above, one of the primary benefits of exercise is improved cardiovascular function, (i.e. increased capacity of the heart to pump more blood per beat, and improved circulation). This adaptation in particular is key in improving immune system function because it results in increased transport of white blood cells that patrol the body for damage, infection, and cancer cells. It not only increases the number of tissues they travel to, but it also gets them there faster.1-2
In terms of muscle adaptation, with each contraction during moderate-to-vigorous exercise, muscles produce and release proteins called cytokines ( also referred to as myokines because they come directly from the muscle) that have anti-inflammatory affects all over the body.3 Although we often think of inflammation as strictly being a bad thing, but it’s actually the balance of inflammatory and anti-inflammatory signals that is a hallmark of a healthy and well-functioning immune system.
In addition, exercise, in combination with a balanced diet, also helps to create a caloric deficit which is important for weight loss. While it’s true that not everyone needs to lose weight, decreasing fat mass is a goal of many, and also has the potential to decrease the kind of inflammation you don’t want.4 This is another piece to maintaining inflammation levels which ultimately improves immune function. When your body limits the number of inflammatory signals, it does a better job of recognizing the right signals at the right time which is the immune system’s main line of communication.
The last example I’ll give is in regard to the endocrine response to exercise. When we exercise, our endocrine system releases chemical signals that also circulate throughout our body. These signals have many functions like telling our heart rate to increase, or our muscles to take in more energy. The release of stress hormones is important for immune function because it not only aids in increased circulation of immune cells by up to 2- to 3-fold within minutes, but it actually helps those cells to function better.4
This only scratches the surface of the benefits of exercise, however. There are more benefits that reach into mental health and circle back to improved immune function,5 but I’ll save that for another article.
Adapted from the Physical Activity, Exercise and Immune Function Factsheet.
- Khoramipour K, et al. (2021) Physical activity and nutrition guidelines to help fight against COVID-19. Journal of Sports Sciences, 39(1):101-107. doi: 1080/02640414.202.1807089.
- Graff RM, et al. (2018) β 2 -Adrenergic receptor signaling mediates the preferential mobilization of differentiated subsets of CD8+ T-cells, NK-cells and non-classical monocytes in response to acute exercise in humans. Brain, Behavior, and Immunity, 74:143-153. doi: 1016/j.bbi.2018.08.017.
- Gleeson M, et al. (2011) The anti-inflammatory effects of exercise: mechanisms and implications for the prevention and treatment of disease. Nature Reviews Immunology, 11:607–615. doi: 1038/nri3041.
- Baker FL, et al. (2021) Exercise to support optimal immune function. American College of Sports Medicine, 25(1):5-8. doi: 10.1249/FIT.0000000000000628.
- Lange KW, et al. (2020) Movement and nutrition in COVID-19. Movement and Nutrition in Health and Disease, 4:89-94. doi: 10.5283/mnhd.33.