Physical activities will be able to resume freely outside but also indoors. Good for our health! Indeed, regular physical exercise has several positive effects on the immune system. For example, regular physical activity of moderate intensity reduces chronic inflammation, promotes the circulation of cells involved in the response to pathogens, improves the activity of these immune cells and slows down the progressive loss of the effectiveness of the immune system. that occurs during aging.
This modulation of the immune system seems to have concrete impacts on the response to pathogens. For example, a systematic review of 14 randomized clinical trials (1377 participants in total) found that the duration and severity of common respiratory infections like colds, flu and sore throats were decreased in people who are physically active. .
The impact of regular exercise on infections like COVID-19 has not yet been studied, but it can be assumed that improving immune efficiency, combined with creating a less inflammatory environment, could protect against more severe forms of the disease which are caused by an exaggerated inflammatory reaction (cytokine storm) which destroys lung cells and blood vessels.
The secret of the effect of sport: a formidable stimulant of the immune system
A study recently published in the prestigious Nature allows us to better understand, at the cellular and molecular levels, this close link between exercise and immunity. The researchers discovered that during exercise, the mechanical forces that are exerted on the bones are detected by the blood vessels present inside these bones, on the periphery of the bone marrow. This mechanical signal has two different but complementary effects.
On the one hand, there is stimulation of stem cells specialized in the production of new bone cells, which could explain why several studies have shown that exercise improves bone stiffness. On the other hand, these bone stem cells produce in parallel a factor which stimulates the growth of precursors of immature immune cells.
In response to movement, there is therefore formation of a reservoir of immature immune cells which can be rapidly mobilized in the form of B and T lymphocytes to neutralize infections. These two populations of stem cells, both those responsible for the formation of new bone cells and the precursors of immune cells, decrease significantly during aging. It is possible that this phenomenon contributes to the bone fragility and reduced immune efficiency often observed in the elderly.
On the other hand, the researchers observed that when the older animal models were subjected to regular exercise sessions (exercise wheel placed in the cage of the mice), the populations of the two types of stem cells increased at the level of the marrow. bone. This mechanism could therefore explain why the effectiveness of the immune system is better preserved in the elderly who regularly engage in physical activity.
Immune cells in stock in case of infection
Regular physical exercise is therefore not only the best way to maintain good physical shape and to prevent the development of a host of chronic diseases, whether cardiovascular diseases, type 2, several types of cancer or age-related cognitive decline. The movement generated during exercise also stimulates the production of immune cells in the bone marrow, creating a niche of lymphocytes which can be recruited in the event of infection and participate in the elimination of the pathogen.
Grande AJ et al. Exercise versus no exercise for the occurrence, severity, and duration of acute respiratory infections. Cochrane Database of Systematic Reviews 2020, Issue 4. Art. No.: CD010596.
Shen B et al. A mechanosensitive peri-arteriolar niche for osteogenesis and lymphopoiesis. Nature, published on February 24, 2021.
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