Our immune system is a highly complex network of cells designed to protect us from infections and diseases. It has been proven that physical exercise has an important and very positive impact on the normal functioning of this system.

Regular practice of physical exercise, of moderate to advanced intensity, demonstrated marked improvements in immune responses to vaccination, reduction of low-grade chronic inflammation and improvements in different markers in individuals with diabetes, cardiovascular diseases, obesity, cancer, HIV, among others.

The current COVID-19 pandemic has raised many questions about how exercise can be beneficial against infections, contributing to greater immunity. This discussion became more pertinent with the limitations in people's daily lives, including, for example, restricted access to gyms and public gardens, where we normally practice physical activity. To make this situation worse, there are the known negative effects of social isolation and confinement on immunity.

Glucocorticoids (hormones directly involved in the stress response), such as cor-tisol, are elevated during these periods and can inhibit many critical functions of our immune system. T cells (immune system cells that also belong to the group of white blood cells) have a viral response to regulate the immune system. When we are under the effects of stress, these cells are reduced, therefore the ability to fight infections or diseases is also reduced.

Another extremely important factor is the fact that cells maintain their ability to reorganize themselves so that they can "watch" vulnerable areas in our body (for example, the upper respiratory system and lungs) to protect the organ. -nism against viruses and other pathogens. This process is also important to minimize the impact of the virus and speed up the viral solution, if we are infected.

Practicing physical activity is especially beneficial for seniors who are the most susceptible to infections in general, but also identified as a population particularly vulnerable to contracting COVID-19.

In short, it is essential to have and maintain constant activity levels, within the recommendations. Physical exercise, in addition to having a direct positive effect on the cells and molecules of the immune system, is also known to counteract the negative effects of stress on immunity. In times of Covid-19 and in the conditions we find ourselves in today, the most important conclusion is to reduce exposure to other people who may be carriers of the virus. However, we should not ignore the importance of staying active and healthy now, in the context of a pandemic, and throughout our lives. Therefore, it is essential that we find ways to continue exercising, maintaining social distancing and appropriate hygiene measures.

Alexandre Ichim