Regular physical activity not only benefits the muscles, lungs, and heart, but also enhances the body’s immune defenses. This conclusion comes from a study involving older adults with long-term experience in endurance exercise, which includes activities such as long-distance running, cycling, swimming, rowing, and walking.

An international group of scientists examined the immune cells of these participants and discovered that their “natural killer” cells, the body’s sentinels against viruses and abnormal cells, were more adaptable, showed lower levels of inflammation, and functioned with greater metabolic efficiency.

Supported by FAPESP and published in Scientific Reports, the study focused on natural killer (NK) cells, a type of white blood cell (lymphocyte) responsible for identifying and destroying infected or diseased cells, including cancer cells. These cells play a vital role in immune defense by recognizing and attacking harmful invaders such as viruses and other pathogens. The team examined blood samples from nine participants with an average age of 64, separated into two groups: those who were physically untrained and those who had practiced endurance exercise.

“In a previous study, we found that obesity and a sedentary lifestyle can trigger a process of premature aging of defense cells. This made us want to investigate the other side of the story, that is, whether an older adult who has been practicing endurance exercises for more than 20 years may have a better-prepared immune system. And that’s indeed what we found. In these individuals, NK cells functioned better in the face of an inflammatory challenge, in addition to using energy more efficiently. Therefore, it’s as if exercise also trains the immune system,” says Luciele Minuzzi, a visiting researcher at Justus Liebig University Giessen (JLU) in Germany.