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Brasilia, Brazil | Hildemar Santo, Doctor and Professor at the School of Public Health, University of Loma Linda, United States

Did you know that overexercise can suppress your immune system? I remember a friend, a marathon runner, who was affected by a “little” cold after a competition. He ended up in the hospital and the thing got worse: he was intubated and had a lung abscess. This occurred in pre-covid times. If it were to happen today, I don't know! But my friend survived.

What is the lesson of this incident? Be careful when running marathons. In fact, in my opinion there are three types of marathon runners: the professional, the crisis of the fifties, and the stubborn. In general, professionals are athletes who have the right body for running and live off the sport, such as Kenyans, for example. The second type are those who are in their fifties and participating in a marathon is something extraordinary that is on your list of achievements before entering the old age phase (these run once and that's it). The third type is stubborn, i.e. people like you and me who think that running marathons is the same as wandering in the mall – these are the ones who have the highest risk of complications.

Anyway, the immune system of these three groups will be affected after a competition and even a training in which the runner approaches 40 kilometers or 24.8 miles (the total course of a marathon is 42 kilometers/26 miles). Thus, the advice is to avoid the “sport” or take pandemic precautions right after it: social isolation, washing hands, wearing masks, and avoiding crowding.

If you run, the “bug” catches! But the other extreme, stopping, also does not offer much more security (the proverb says that the “bug eats”). Thus, the most advisable exercise to activate the immune system, activate circulation and pulmonary function would be an outdoor walk, preferably in natural environments where there are enough trees and few people, or some other type of moderate exercise.

Always on the move

The best exercise is the one that moves the lower limbs. Yes, the legs. Running is beneficial, but maybe not the 42 kilometers (26 miles) in an “episode!” Walking, however, offers the same advantages without any risk, except tripping and falling – please choose a flat place without holes!

The main mechanism of exercise for the prevention of Covid-19 is due to the circulation of immune cells. When a person is inactive, these cells become stagnant in the organs of lymphatic production (which produce lymphocytes, white blood cells responsible for fighting infections). Thus the spleen, bone marrow and even the tonsils will be saturated with these cells.

When the person starts exercising, the blood begins to circulate faster and the cells go into circulation and there is an increase of them in other organs, especially the respiratory and lungs. This confers increased immunity to the individual. According to Dr. David Nieman, a specialist and researcher in physical activity and the immune system, exercise can activate immunity by almost 50%.

Daily prevention

Another factor would be aerobic capacity. That is, when a person exercises, there is an increase in oxygen absorption and an increased ability to withstand low volumes of oxygen. Thus, when someone acquires a respiratory infection, there is an increased capacity of the lungs in case there is a greater need for oxygen.

This is exactly what happens with the coronavirus. It affects lung cells and creates an inflammatory environment, decreasing pulmonary circulation and causing a greater need for oxygen. Today it is known that people who are affected by Covid-19 may have an oxygen pressure (pO2) of 50% (normal would be above 90%). Thus, regular and moderate physical exercise can help prevent the complications brought about by the pandemic.

So my friend, whether you are vaccinated or not, keep up with your daily exercise, and why not include an outdoor walk in the park, on the beach or on the mountain?

“A walk even in winter can produce more health benefits than any medication a doctor may prescribe” (Ellen White, Testimonies for the Church 2:529).

This article was originally published on the South American Division’s Portuguese news site