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Study: does exercise provide protection from infection?

Research says yes, but runners should be careful not to over-do it

Running When Sick

Since the onset of the pandemic, improving the health and strength of our immune systems has been on everyone’s minds. When scientists and health experts pointed out that regular exercise helps improve immune function, runners collectively breathed a sigh of relief, but exactly how much of an effect does exercise really have? Recent research reveals that while it does provide some infection protection, exercise is far from a cure-all for disease, and over-doing it can actually have the reverse effect.

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The study

The researchers noted that there is a general consensus that regular bouts of short-lasting (up to 45 minutes) moderate intensity exercise is beneficial for immune defense, particularly in older adults and people with chronic diseases. By contrast, they added that high-performance athletes have a much higher instance of illness, and it is second only to injury for the number of training days lost during a season.

The goal of this review, published by the Association for the Advancement of Sports Medicine, was to determine the reason why high-performance athletes tend to get sick more than the general population, and to determine how much exercise really improves immune function by analysing all of the available literature on the topic.

Exercise and immune function

Upon reviewing the research, it is undeniable that regular bouts of moderate to vigorous physical activity are beneficial for the normal functioning of the immune system, which likely helps lower (although not completely eliminate) your risk for contracting respiratory illnesses and some cancers. This is because with each session of physical activity, you increase the frequency with which immune cells are exchanged between the blood and other tissues. This, experts believe, likely contributes to enhanced immune surveillance, improved health and a lower risk of illness.

Whether or not athletes are more susceptible to illness and infection is still cause for debate among scientists, but those on both sides of the argument agree on one thing: “factors such as stress, sleep, nutrition, circadian misalignment and infection/vaccination history could directly impact or contribute to impaired immunity and infection risk, particularly in situations when pathogen exposure is more likely.”

In other words, it may not be that large amounts of intense exercise directly reduces the functioning of your immune system, but rather the added stress on your body, combined with other lifestyle factors, could be putting you at greater risk for illness.

How can runners protect their immune systems?

Runners, even if they’re not elite or high performance athletes, are more likely to fall into that at-risk group because of the amount of running they do. Running multiple days each week can take a toll on your body, even if you’re not at the elite level.

Does this mean you should stop running? No. Running can still be beneficial to your immune system, as long as you’re taking care of your body and recovering properly. Take a look at this infographic Michael Gleeson, professor of exercise biochemistry at Loughborough University (UK):

Photo: Michael Gleeson

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As you can see, reducing your risk for illness and infection requires a multi-faceted approach, and while exercise isn’t a bullet-proof vest, it can do wonders for your immune system. If, however, you’re training for a goal race and doing a lot of volume or high-intensity work, you need to take extra care and make sure that you’re managing your stress load and recovering properly. This will reduce the number of training days you’re forced to miss because of illness, and allow you to continue running well.