Engaging in regular, moderate physical activity (30 to 60 minutes per day) strengthens natural defenses by improving the circulation of protective cells and reducing stress (cortisol). Conversely, effort that is too intense or prolonged may create an "open window" of temporary vulnerability to infections.

noli's read

The idea that moderate physical activity supports our natural defenses is solidly validated by research. A meta-analysis by Nieman and Wentz (2019) in the *Journal of Sport and Health Science* confirms that regular exercise of 30 to 45 minutes stimulates the circulation of active immune cells. Furthermore, the regulatory effect of exercise on cortisol (the stress hormone) directly contributes to preserving our general vitality. However, the analogy between the rise in body temperature linked to exertion and the fever mechanism for neutralizing viruses is scientifically exaggerated and unproven in humans. Regarding the "open window" theory after intense effort, a review by Campbell and Turner (2018) published in *Frontiers in Immunology* strongly nuances it: immune cells do not decrease, they simply relocate elsewhere to better monitor the body. The final advice to aim for moderate daily movement therefore remains excellent for bodily balance.

the sources

1. 1Campbell JP, Turner JE 2018