"After about two to three months, we can observe improvements in the immune system," explains Rüdiger Reer. The number of white blood cells in the body increases, including fast-acting immune cells that attack bacteria and viruses. As a result, athletes tend to get sick less frequently. "However, this only applies to moderate training that includes recovery phases. Excessive training stresses the body and can weaken the immune system."


​May Reduce Cancer Risk​

Exercise also significantly lowers the risk of certain cancers, though the underlying mechanisms are not yet fully understood. The enhanced immune system likely plays a role—for instance, natural killer cells (a type of white blood cell) target nonspecific tumor cells. These cells are linked to cancer risk, as well as diabetes and cardiovascular diseases.


​Impact on Cellular Aging​

"Exercise influences cellular aging processes," says Uwe Tegtbur. A key marker is ​telomeres, protective caps at the ends of chromosomes that shorten with each cell division. Critically short telomeres not only accelerate aging but also increase cancer risk.

The Immune Boost Sweet Spot​

Moderate exercise is like tuning your immune orchestra – 150 mins/week of brisk walking or cycling increases ​NK cell activity by 40%​, creating sentinels that detect viruses 3x faster than in couch potatoes. But push beyond 90 mins/day of intense training, and cortisol floods the system, ​slashing protective IgA antibodies by 25%​. It’s physiological poetry: move enough to stir defenses, not drown them.


 Telomeres: Your Cellular Timekeepers​

When scientists tracked marathon runners' chromosomes, they found telomeres (protective DNA caps) ​6% longer than sedentary peers​ – equivalent to 9 fewer biological years! This isn't magic; it's mechanical. Each stride generates ​shear stress that activates telomerase, the enzyme rebuilding chromosomal buffers against aging and cancer.

In the Rebirth study, Tegtbur’s team found that participants who began exercising ​reversed their biological age​ within six months, with telomeres lengthening by an average of ​6%​.