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Why Your Immune System Is Affected By Strenuous Exercise + What To Do About It

Merrell Readman
April 28, 2022
Merrell Readman
mbg Associate Food & Health Editor
By Merrell Readman
mbg Associate Food & Health Editor
Merrell Readman is the Associate Food & Health Editor at mindbodygreen. Readman is a Fordham University graduate with a degree in journalism and a minor in film and television. She has covered beauty, health, and well-being throughout her editorial career.
Athletic Woman Running On Street In Sunlight
Image by Javier Díez / Stocksy
April 28, 2022

This past weekend I ran a half marathon. For months I had been training to the best of my ability, pushing myself on long runs every weekend and racking up mileage throughout the week. Before any big race, you're supposed to taper in the days leading up, allowing your body to rest and recover before the big performance. So, I followed directions and cut my mileage. But as the week went on and the race inched closer and closer, I could tell my immune system wasn't exactly thriving—and I promptly began to panic. 

After the race came and went without a hitch, the realization that I wasn't feeling my best became more difficult to ignore. With some research, I found that it was actually quite normal for your body to crash when you finally slowed down after bouts of intense activity. To further understand how my immune system was affected by the half marathon and what I could do to buffer against this decline the next time, I spoke with Michael J. Stephen, M.D., who explained the effects of a difficult workout on the body and why you may feel less than great after hitting a PR.

How exercise affects your immune system.

We know that on the whole, exercise is great for your body for a number of reasons. Not only can it help boost your mood and improve longevity, but regularly working out may actually be useful for keeping you healthy and strengthening your immune system, as well. "There are studies1 that show [our body's defensive] cells, like neutrophils and macrophages, circulate more efficiently when one engages in regular physical activity," explains Stephen.

However, overexerting your body is another case entirely. While training for a half marathon or marathon is entirely doable, it places a lot of stress on not only your muscles but also your immune system. "During your effort you have released stress hormones like cortisol2 and epinephrine, and we know too much of these hormones negatively affect the body's immune cells," says Stephen. "[The immune cells] are not as effective after being exposed to elevated levels of stress hormones."

Training for these intense physical feats certainly prepares your body to complete them with increased ease, but that doesn't mean you're totally safe from overexertion. "The vast majority of people underestimate how much damage they have done to their body with a big physical effort and subsequently underestimate how much time is needed for your body to heal," Stephen adds.

Allotting proper recovery time after a race is essential to your long-term health, and just because you're not feeling depleted immediately doesn't mean you don't need a rest. "One needs to be very careful and build back up slowly after a big physical effort, or else your body is going to rebel, and your training will be set back many months," Stephen warns. If you're not feeling your best after a big race, you may simply have pushed your body to the brink, and it can require a few days to bounce back from the strain.

How to proactively buffer an immune crash.

Reduce stress.

Now that I've completed one half marathon, it's safe to say I was bit by the running bug and already feel eager to start training for another race. But if at all possible, I would love to minimize the impact on my immune system. So, what can you do to avoid this phenomenon?

According to Stephen, the best way to maintain your well-being coming out of a tough training session or race is by tapering your activity slowly so your body can adjust to the new benchmark, giving your immune system time to prepare. "Taper slowly, build back up slowly, and really put an effort into good nutrition, proper sleep, and hand-washing," he explains. "A positive attitude and keeping busy and happy with other parts of your life can also help tremendously as this keeps stress hormones low."

Try an immune-targeted supplement.

Preemptively caring for your immune system (aka being proactive versus reactive) is a great way to keep feeling your best during training. Certain supplements like mbg's immune support+ can help support a healthy and resilient immune system by enhancing your body's antioxidant defenses and priming your immune cells for action.* In addition to vitamins C, D3, and zinc bisglycinate, this unique combination formula delivers bioactives quercetin and beta-glucan. Take vitamin C, for example, which supports the normal development and function of immune cells, the inflammatory response, and healing—all great benefits for any athlete.*

The bottom line.

While your muscles and cardiovascular system may be prepared for that intense race you've been training for, it's important not to neglect your immune system while striving toward your goals—be it a half marathon or any other strenuous athletic endeavor.

Take care to protect your body before a race and nurture your immune system, by minimizing stress and taking supportive nutrition measures. That way, you can rest assured that you'll be putting your overall well-being first, as you work toward any fitness pursuits.

Merrell Readman author page.
Merrell Readman
mbg Associate Food & Health Editor

Merrell Readman is the Associate Food & Health Editor at mindbodygreen. Readman is a Fordham University graduate with a degree in journalism and a minor in film and television. She has covered beauty, health, and well-being throughout her editorial career, and formerly worked at SheFinds. Her byline has also appeared in Women’s Health. In her current role, she writes and edits for the health, movement, and food sections of mindbodygreen. Readman currently lives in New York City.