Apparently, various endurance exercise habits train not only your muscles and cardio but also your immune system’s natural killer cells. Who would have thought that pushing through a few miles on the trails or on the bike would help train immune cells to keep balance in the later years? Earlier studies often indicated that after a big race, athletes were at higher risk of viral infections, but in this study, over time, long term athletes clearly trained their immune systems to fight infections without overdoing the inflammatory response.
We all want a good defense system in our bodies which can take care of the myriad viruses, bacteria, and parasites we encounter every day. When we stop and really think about it, we not only want it to be effective and fast at killing these infections, but we also want it to do so without causing so much inflammation that our own tissues or organs get damaged. COVID 19 brought many instances of excessive inflammation causing as much or more damage than the infection itself due to the immune system getting carried away. We want enough but not too much inflammation to do the job.
In this study, scientists identified different responses to immune challenges in a type of lymphocyte (immune cell) called a natural killer cell. These cells along with multiple other immune cell types patrol our blood stream and body for infectious threats. The natural killer cell focuses its attention more on viruses and cancer cells, destroying cells with viruses or cancer markers once those cells are recognized. Like other immune cells, in order to do a “good” job of defense, they must kill the right target while causing little to no damage to normal cells around them.
Prior research had linked sedentary lifestyles and obesity with what they called “premature aging” of the defense cells. This group wanted to look at the other end of the activity spectrum to discover if endurance exercise over years of training had any effects on the immune defenses. They were please with their findings that these natural killer cells appeared stronger and more balanced in the test subjects who had performed some type of endurance exercise for 20 years or more.
To put the findings into straightforward language, the endurance athletes’ natural killer cells were better able to control their inflammation responses than the natural killer cells from younger athletes. The researchers measured in a variety of ways. When looking at the chemical responses of these cells, the endurance athletes’ natural killer cells had fewer inflammatory markers and more anti-inflammatory markers in response to infections. Then, when they attempted to alter the natural killer cells’ responses to these infections with 2 different drugs, the longer-term athletes’ cells still demonstrated more robust responses. In these tests, the untrained natural killer cells demonstrated more cellular exhaustion or inflammation failure.
In the end, with the support of other experiments, the researchers assert that exercise over years trains natural killer cells to have better adapted to stress responses. The exercise serves as a controlled stimulus to mature them so that over years, they are more resilient and work in a more controlled fashion when the real danger comes along with infections.
To help our patients live healthier, more abundant lives, we deal with a multitude of dysfunctions that have built up over some period of time. While we are thankful for the opportunity to restore health already broken, we appreciate studies like this which point us towards ways to prevent future illness and guide future generations into healthier adulthoods. We now know that adding some exercise to the weekly routine will not only help muscles, joints, and hearts, but will also strengthen immune systems, and this knowledge helps us equip the younger generation for better immune health in coming decades.
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Original Article:
Luciele Guerra Minuzzi, Helena Batatinha, Christopher Weyh, Vidya Srokshna Balasubramanian Lakshmi, Carmen Fiuza-Luces, Beatriz G. Gálvez, Alejandro Lucia, Ana Maria Teixeira, Natascha Sommer, José Cesar Rosa-Neto, Fabio Santos Lira, Karsten Krüger. Natural killer cells from endurance-trained older adults show improved functional and metabolic responses to adrenergic blockade and mTOR inhibition. Scientific Reports, 2025; 15 (1) DOI: 10.1038/s41598-025-06057-y
Thanks to Science Daily:
Fundação de Amparo à Pesquisa do Estado de São Paulo. “Exercise might be the key to a younger, sharper immune system.” ScienceDaily. ScienceDaily, 14 October 2025. <www.sciencedaily.com/releases/2025/10/251014014421.htm>.
Sanctuary Functional Medicine, under the direction of Dr Eric Potter, IFMCP MD, provides functional medicine services to Nashville, Middle Tennessee and beyond. We frequently treat patients from Kentucky, Alabama, Mississippi, Georgia, Ohio, Indiana, and more... offering the hope of healthier more abundant lives to those with chronic illness.
Dr. Eric Potter graduated from Vanderbilt Medical School and then went on to specialize in internal medicine (adult) and pediatric care, spending significant time and effort in growing his medical understanding while caring for patients from all walks of life.
