Surprising reason you should exercise when sick

When it comes to exercise and immunity, we know that regular exercise at a moderate pace can boost immunity and keep the winter bugs at bay. Now, new research questions the widespread belief that strenuous exercise (think marathons) can actually increase susceptibility to infections due to immune system depression.

Clarifying misconceptions

A recent review published in the Journal Frontiers in Immunology looked to clarify common misconceptions regarding the relationship between exercise and the immune system that have formed over the years.

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In their study, the authors explain that for many years we’ve understood immune cells change in two ways following exercise. First, the number of ‘natural killer’ immune cells (which deal with infection) increase immediately. The new research has proved this to be the case.

What the research has now disproved though is the belief these natural killer cells decline dramatically in the hours and days post exercise.

Until now, this “open window theory” gave us the understanding that our immune system would be compromised as our body recovers post workout — and we could be more susceptible to infection during this time.

But the new research has blown away this theory.

“In fact, evidence now suggests that your immune system remains boosted after exercise — for example we know that exercise can improve your immune response to a flu jab,” says study co-author, Dr James Turner.

The researchers believe that the cells are not ‘destroyed’ (as previously thought), instead the cells migrate to other parts of the body, looking for other infections, such as the lower respiratory tract (chest or lungs), representing an immune boost, making it less likely for infections to flourish.

“Given the important role exercise has for reducing the risk of cardiovascular disease, cancer and type 2 diabetes, the findings from our analysis emphasise that people should not be put off exercise for fear that it will dampen their immune system.”

However, that doesn’t mean you’ll never catch a cold again if you’re an avid gym goer. The study’s authors cautioned that a poor diet, getting cold and wet, and psychological stress were linked to an increased risk of developing infections.

They also added that visiting public places with large gatherings of people, public transport, particularly airline travel over long distances, where sleep is compromised, might also increase infection risk.

It’s also important to note that while a brisk walk or strenuous workout is not going to dampen your immunity, excessive exercise might. Too much exercise can make you overtired and not as resilient. Problem is, if you don’t take time for proper R&R — a problem likely to be exacerbated if you don’t get enough sleep every night — can run you down.

How sick is too sick to exercise?

You’ve got a few sniffles: If you’re sneezing a bit but otherwise feeling well, you don’t need to starve a cold of exercise. Keep up your workout but maybe reduce the intensity a bit. Instead of your usual run, take a walk, do a little stretching, but don’t use it as an excuse to throw in the fitness towel.

You’ve got a fever: Now is the time to listen to your body and rest. The function of a fever is to kill off most bacteria and viruses and throwing exercise into the mix can further elevate your internal temperature, making you even sicker. Intervals to the kitchens for cups of tea and Netflix marathons are highly recommended at this point.

Influenza or stomach flu: It’s important to avoid the virus spreading, so when you have widespread fatigue, muscles and joint aches or gastroenteritis, stay inside. As you’re recovering, it’s fine to start exercising again — but ease back into it gradually. Avoid pushing yourself too hard too soon to make up for lost time.

Bottom line

Of course, the best case scenario would be — avoid getting sick in the first place. It helps to:

Eat a well balanced diet

• Keep hydrated

• Manage stress

• Get ample shut-eye (for most people around 7-8 hours a night)

• Practice good hygiene — hand washing, stay away from sick people

• Exercise regularly — avoid overtraining and balance your workouts with adequate rest and recovery.

Kathleen Alleaume is a nutrition and exercise scientist and founder of The Right Balance. Follow her on Twitter: @therightbalance

Read more about Jessica Sepel’s recipe for a detox immunity gut-booster, and the pre-meal soup that can suppress your appetite.

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