Exercising sick could be a “wrong good idea”.

It’s a tried and true idea: Regular exercise is good for your immune system. In fact, some research suggests it may reduce the risk of an upper respiratory tract infection like the common cold. All you need is 30 minutes of moderate exercise five times a week to reap the benefits.

Since exercise is good for our immune system, some people may think that exercise can help “flush out the disease” when they are sick. Unfortunately, with a cold, for example, there is no evidence that exercise during an illness can shorten it or make it less painful…

A well explained upstream benefit

There are several reasons why physical exercise is good for our immune system.

The first can be partially explained by the hormones released during exercise. These are the catecholamines, better known for their most well-known representatives, adrenaline and noradrenaline. These hormones play an important role in the functioning of our immune system by causing the rapid release of key immune cells that help detect the presence of viruses or other pathogens in the body.

Nordic Walking Increasingly Popular Among Seniors – Pxhere.com CC0

They also increase the number of times our immune cells transfer between the blood, where they circulate, and the tissues where they may need to intervene — which is important in helping them detect and prevent disease caused by viruses or other pathogens will. Research shows that exercise is one way to increase levels of these vital hormones in our bodies.

Second point, when we engage in a sporting activity, blood flow increases to help our body cope with the increased demands of exercise. This high blood flow puts more strain on our blood vessels, which releases specific immune cells from the lymphocyte family, natural killer cells, and T cells. These lymphocytes, which can rest on the walls of our blood vessels, both play important roles in destroying virus-infected cells in our body.

Physical activity can have other positive effects on our fight against infection. For example, older people who exercised regularly for a month healed skin wounds faster than members of a control group who did not exercise. This faster healing process reduces the risk of viruses and bacteria entering the body through skin wounds.

All of these mechanisms together can improve our immune response and thus reduce the risk of infection. And you don’t have to be a regular at the gym to reap the benefits. Studies have shown that when non-exercise people started brisk walking regularly for 40 to 45 minutes five days a week, their symptoms of upper respiratory tract infection decreased by 40 to 50% compared to a control group .

Regular brisk walking is enough to limit respiratory infections
Regular brisk walking is enough to limit respiratory infections – L. Balajadia/Shutterstock (via The Conversation)

What if you are already ill?

Despite these benefits, it’s unclear whether exercising when you have a cold will help you shed your tissues faster than not doing it.

So far, no study has really addressed the question, mainly because it would be difficult to conduct such a study – especially since a proportion of the participants would have to be infected with a virus to determine whether the exercise has an effect or not. That would not only be difficult to achieve, but also ethically questionable.

But since exercise is good for the immune system, why can’t exercise during an infection improve our defenses? It seems logical…

Well, it’s important to remember that exercise can put a strain on the body. While beneficial in certain circumstances, it can also make immune cells less able to respond to pathogens. Part of that may be because when you exercise, your body needs more oxygen and stored energy (in the form of glucose) — which our immune cells also need to fight. If the body fights an existing infection and is exposed to physical exertion at the same time, the immune response does not necessarily benefit when energy resources have to be shared.

Running is one of the most popular physical activities
Running is one of the most popular physical activities – RennanMourao / Pxhere.com CC0

But if there is currently no evidence that exercising can help you recover faster from a cold, that doesn’t necessarily mean you shouldn’t! There are just a few precautions to take.

First of all, there are some cases where exercise is not advisable: if you have a fever, muscle pain or vomiting, etc.

Then you need to know how to listen to your body. If your symptoms are mostly above the neck (like a runny nose or stuffy nose), start exercising at a lower intensity than usual to see how you feel. If all goes well, you can gradually increase the intensity. But if that extra activity makes you feel worse, stop exerting yourself and rest.

One more thing: Think of yourself, but also think of others! If you want to exercise while you’re sick, do it… but be careful when you’re around other people. Respiratory infections (colds, etc.) are contagious, so it is best not to go to the gym or gym and exercise outside or at home so as not to infect the neighbors.

Regular exercise is a great way to prime the immune system to fight off various types of infections, including the common cold and maybe even Covid… But don’t feel like you need to exercise when you’re sick and tired. Rest and adequate fluid intake is often the best remedy for a cold. If you were active before, you limited your risk of finding yourself in this uncomfortable situation…

This review was written by John Hough, Lecturer in Exercise and Exercise Physiology at Nottingham Trent University (England).
The original article has been translated (from English) and published on the website of The conversation.

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