Exercise and Immunity: Which Form is Best?

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When Robb Feldman’s doctor told him during a recent well-check that one of the best methods for protecting his immune system against onslaughts was nothing more than good old-fashioned exercise, Robb’s mind immediately homed in on the “extreme” sports he had enjoyed in college.

“I’m serious, I thought I was going to have to get into ultramarathons or something,” said the 43-year-old father of two. “But she told me that ‘moderate exercise is what I should be doing; in fact, she made a point of saying it shouldn’t be anything extreme, which is exactly what my wife wanted to hear,” he laughed.

Image Credit: @Mohamed Hassan - Pixabay

Exercise and the immune system go hand in hand and these days, it’s more important than ever to maintain a strong, healthy immune system. Many people are looking for natural ways to safeguard theirs.

While there is no magic formula for supercharging immunity, there are a number of lifestyle changes that may optimize your body’s natural defenses and help you fight harmful pathogens, or disease-causing organisms. 

Today we’re going to talk about exercise and the immune system, but why not also take a look at what we’ve previously written around how to boost your immune system?

Science Supports Exercise

It’s probably safe to say that most people would prefer to make it through cold season without getting knocked down by a nasty cold (or three). Whilst there are immune system booster supplements that you can take, no one has yet figured out how to prevent colds entirely, one scientifically proven way of optimizing our defenses against illnesses such as the common cold is with exercise.

Why? Well, scientists aren’t exactly sure, but there are several theories as to why exercise works to keep our immune system running smoothly.

For example, this study published in the American Journal of Medicine found that women who walked for a half-hour each day for one year had fewer than half the number of colds as those who didn’t exercise. Researchers found that regular walking may lead to a higher number of white blood cells, which fight infections.

Other studies have also found a strong link between exercise and immunity, including the ability of just 20 minutes of exercise to reduce inflammation as well as the effects of nutrition on our immune system’s response to exercise.

Image Credit: @PublicDomainArchive - Pixabay

As the authors of this study point out, “exercise has a profound effect on the normal functioning of the immune system.” In fact, Exercise Immunology, although a relatively new field of scientific endeavor (with a few notable exceptions, such as this 1950 study and this one from 1902!), has developed into a rather robust area of inquiry over the last several decades.

However, people are sometimes surprised to learn that not all forms of exercise are recommended for immune system support; in fact, some ways can be downright detrimental. Simply put, there appears to be a “right way” and a “wrong way” to exercise when it comes to maintaining a good level of immunity.

What Does This Mean?

In line with what Robb’s doctor told him at his last annual physical, what researchers have found is that regular moderate intensity exercise is immuno-protective and that, in addition to protecting our health over the long run, regular short bursts of activity give our immune system a temporary boost by creating a heightened state of immune surveillance and immune regulation.

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Moderate-intensity exercise will also lower stress hormones such as adrenaline and cortisol, further reducing the chances we will get sick (we’ve written more about how stress affects your immune system here).

At the same time, it is generally accepted that prolonged periods of intense exercise can actually decrease our immunity. For example, intense exercise is associated with an increased risk for upper respiratory tract infection while moderate exercise has been associated with a decreased risk. The study researchers found that exercise stress was associated with an increase in susceptibility to influenza infection in terms of morbidity, mortality, and symptom severity.

So what gives?

In a nutshell, when you exert yourself, your body interprets it as some type of physiological stressor. As a result, your body deploys an Army of cells – in particular, T-cells and natural killer (NK) cells – from different parts of your body to flood your bloodstream in preparation for a fight, enabling any threats to be more easily detected and destroyed.

When you are finished with your workout, the blood levels of these cells drop back down to normal (or even below-normal), as they proceed to other body parts to continue a period of heightened immune surveillance which lasts for a couple of hours.

On the other hand, vigorous exercise of long duration – say, 90 minutes or more of hard running – will start to overstress your immune system. This can temporarily impair its ability to do its job by decreasing the number of infection-fighting white blood cells while simultaneously increasing stress hormones like cortisol, all of which may interfere with the normal workings of your immune cells.

Although the physiological effects of heavy exertion on the immune system point towards immunosuppression (at least for the short term), there is one thing on which researchers agree: regular, moderate exercise gives you the best chance of staying healthy long-term.

Bottom Line

Exercise is good for you, but make sure not to overdo it. As the authors at MedlinePlus point out, people who already exercise should not exercise more or harder if the goal is just to increase their immunity. In fact, heavy, long-term exercise can actually cause more harm than good when it comes to your immune system.

The key is to come up with a moderately energetic routine that you’ll stick to; no ultra-marathons necessary.

Image Credit: @bedrck - Pixabay

So What Should You Do?

According to HHS.gov’s Physical Activity Guidelines for Americans, for substantial health benefits, adults should do at least 150 minutes (2h30m) to 300 minutes (5h) of moderate-intensity exercise each week.

A few examples of all you might need to keep your immune system healthy and strong include 20-30 minutes stints of: bicycling, brisk walking, swimming, light hiking, or jogging at a comfortable pace.

Even golfing counts, as long as you walk the course, of course.

Documentation

Campbell, J. P. & Turner, J. E. (2018). Debunking the myth of exercise-induced immune suppression: Redefining the impact of exercise on immunological health across the lifespan. Frontiers in immunology, 9, 648.

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.

Dimitrov, S., Hulteng, E., & Hong, S. (2017). Inflammation and exercise: Inhibition of monocytic intracellular TNF production by acute exercise via 𝛃₂-adrenergic activation. Brain, behavior, and immunity, 61, 60-68.

Harvard Men’s Health Watch. (n.d.). Exercising to relax. Accessed on June 22, 2020.

HHS.gov. President’s Council on Sports, Fitness, and Nutrition. Physical activity guidelines for Americans. Accessed on June 23, 2020.

Horstmann, D. M. (1950). Acute poliomyelitis: Relation of physical activity at the time of onset to the course of the disease. The Journal of the American medical association, 142(4), 236-241.

Larrabee, R. C. (1902). Leukocytosis after violent exercise. The journal of medical research, 7, 76-82.

MedLine Plus. (2018). Exercise and Immunity. Accessed June 22, 2020.

Murphy, E. A., Davis, J. M., Carmichael, M. D., Gangemi, J. D., Ghaffar, A., & Mayer, E. P. (2008). Exercise stress increases susceptibility to influenza infection. Brain, behavior, and immunity, 22(8), 1152-5.

Nieman, D. C., Lila, M. A., & Gillitt, N. D. (2019). Immunometabolism: A multi-omics approach to interpreting the influence of exercise and diet on the immune system. Annual review of food science and technology, 10, 341-363.

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.

Simpson, R. J., Kunz, H., Agha, N., & Graff, R. (2015). Exercise and the regulation of immune functions. Progress in molecular biology and translational science, 135, 355-380.

WebMD. (2020). Exercise and the common cold. Accessed on June 22, 2020.

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