Physical endurance trains the immune system

A study published in the journal Scientific Reports showed that in older people who have been regularly engaged in endurance sports (running, swimming, cycling or walking) for more than 20 years, the cells of the natural immune system — the so—called natural killer (NK) – work differently. They turned out to be more stable, less prone to inflammation, and more energetically capacious.

NK cells are the body’s first line of defense. They destroy viruses and damaged cells without waiting for signals from other parts of the immune system. Their activity usually decreases with age, but for trained people it turned out to be the opposite.

“We found that in older people who lead an active lifestyle, NK cells not only cope better with inflammation, but also use energy more efficiently. We can say that physical activity also trains the immune system,” explains Luciele Minuzzi, a researcher at the Justus Liebig University in Giessen (Germany).

Scientists compared the blood of nine people aged about 64 years: half led an active lifestyle, the other — sedentary. In the former, the cells turned out to be noticeably younger and more flexible. Even when the researchers blocked key signaling pathways with drugs (propranolol and rapamycin), the immune cells of the trained participants retained the ability to respond to the threat, while those of the untrained ones quickly tired.

Professor Fabio Lira from the University of Sao Paulo State adds:
“Those who exercise regularly have fewer inflammatory markers and more anti-inflammatory ones. This suggests better control of inflammation, which is especially important in old age.”

Other work by the same group confirms that prolonged physical training promotes a “smart” inflammatory response. In older athletes, inflammation does not disappear, but it becomes more balanced — the body reacts only to serious stimuli and avoids chronic inflammation, which is often associated with aging and many diseases.

Experts call this “immune training”: long-term physical activity forms a more mature and stable immune system that protects the body without excessive reactions.