The Athlete’s Immune System: Part 1

Tom Phillips Cyclocross Athlete immune system

Does your training plan address the needs of your immune system? Perhaps it should. You’ve trained for months, diligently following your plan, logging miles and / or time in the gym. You’re prepared to test your limits, land a PR and perhaps a spot on the podium. But, you’re probably NOT planning to get sick. However, if your training plan ignores your immune system, your post-race days could be filled with more than just memories, but also illness. In this two part post, I’ll explain why —and what you can do about it. 

Athletes at Risk for Illness? Doesn’t Exercise Boost the Immune System?

Yes, it does! According to research moderate exercise is a potent preventative tool, potentially reducing your number of sick days by 25-50%. Studies have shown that a little goes a long way, no matter your age. In kids, as little as just six minutes of exercise has been shown to boost the levels of circulating immune cells by nearly 50 percent. Conversely, a study of elderly women showed that simply walking a half-hour each day reduced their risk of getting an upper-respiratory illness during the fall season from 50% down to 20 percent. And, conditioned runners lower their risk to just 8 percent!

Exercise Helps You Bring Your Immunoglobulin, Type A-Game!

Immunoglobulin, type A, or simply IgA, is your first line of defense against infections. It provides a protective barrier to our mucosal surfaces, such as eyes, nostrils and mouth. These moist areas are where most infections start. So, IgA is considered a vital immunological barrier against respiratory tract infections, such as pneumonia and influenza. And, it turns out that moderate exercise (thirty minutes three times a week), boosts IgA levels by 50%!

So, If Moderate Exercise Is Good, More Is Better, Right?!

Easy tiger! Your immune system doesn’t really work that way. While regular, ‘moderate’ (key word here) physical activity improves your immune system’s function and lowers your risk for respiratory infections, sustained and intense exertion may be another story. Just as overtraining and excessive stress can diminish physical performance, they can also hinder immune function, increasing risk of infections. In fact, just one single bout of extreme exertion can drop your IgA levels. So, it’s not surprising that in the weeks following marathons or ultramarathons, runners report a two- to sixfold increase in upper-respiratory-tract infections. Been there?

What Can An Athlete Do To Avoid Respiratory Illness?

According to Dr. Michael Greger, athletes striving to avoid illness need more than the typical cold and flu season recommendations; get a flu shot, avoid touching your eyes or picking your nose, and stay away from sick people. These steps, which will help you avoid picking up whatever illnesses are getting passed around, may not be enough for an athlete.

In his recent book. ‘How Not to Die, he explains that very often respiratory infections are the result of latent viruses already in our body. The right (or wrong) conditions, a temporary dip in immune function from stress, overtraining or a big race can bring that latent virus off the reserve list, putting it back in action —and you on the sidelines. Stay tuned for part two of this post, ‘7 Immune Boosting Tips for the Athlete.’

Are you an athlete (or know one) who has struggled with illness during training and after competition? If so, share your experience and leave a comment below!

Image credit: Lisa Miller


Greger, Michael, MD; Stone, Gene. How Not to Die: Discover the Foods Scientifically Proven to Prevent and Reverse Disease. Flatiron Books, 2015.

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Nieman DC, Henson DA, Gusewitch G, et al. Physical activity and immune function in elderly women. Med Sci Sports Exerc. 1993;25( 7): 823– 31.

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