Lack of exercise leads to premature aging of immune cells? "Exercise is not just for muscles" - A new discovery shows that endurance training "rejuvenates" the immune cells of the elderly

1. How True is "Exercise Boosts Immunity"?

"Exercise boosts immunity." It's a familiar phrase in health information, but the specific changes in immune cells are surprisingly not well-known.

A study published in the scientific journal Scientific Reports in July 2025 provided a detailed insight into this mechanism.santelog.com

This study, introduced by the French medical media "Santélog," focuses on **"natural killer (NK) cells" in the elderly**. NK cells quickly attack virus-infected or cancerous cells, acting like "innate bodyguards."santelog.com

2. What Nine Elderly Individuals Around 64 Years Old Taught Us

The study involved nine elderly participants with an average age of 64.

• A group that has been engaging in endurance training for years, such as running, cycling, swimming, rowing, and brisk walking

• A sedentary group that has done little exercise

These are two contrasting types.santelog.com

The research team exposed NK cells extracted from participants to various conditions in the laboratory, observing in detail their functioning and energy usage. It was revealed that the NK cells of those who continued endurance training were--

• less prone to inflammation

• able to respond quickly when needed

• efficient in energy metabolism

These characteristics resemble those of a "well-trained soldier."santelog.com

3. Even When Blocking Signals with Drugs, the Trained Group's Immunity Remains Resilient

What makes this study unique is that it also examined reactions when immune signals were intentionally "disrupted" by drugs. Researchers used

• "Propranolol," which blocks sympathetic nervous stress signals

• "Rapamycin," which inhibits the mTOR pathway crucial for cell growth and metabolism

to check how well NK cells could maintain their function.Nature

The results showed that--

• the NK cells of elderly individuals with exercise habits maintained their function to a significant extent even when signals were blocked

• while the NK cells of sedentary elderly individuals tended to become exhausted or lose control over inflammation under the same conditions

were observed.santelog.com

In other words, long-term endurance training may lead to "immunometabolic adaptation," allowing immune cells to continue functioning in a balanced manner even when exposed to stress or drugs.

4. How Did Social Media React? From "Exercise is a Panacea" to "Only 9 Samples?"

When this article was introduced in European media, reactions quickly spread on social media platforms like X (formerly Twitter) and Instagram (the following are summarized impressions of typical reactions).

• "Exercise not only trains muscles but also immunity, it's practically a 'panacea'."

• "Even at 64, if you keep running, your immune cells stay healthy, it's nothing but hope."

• "Nine samples are certainly few, but the direction is convincing. I'd like to see a larger-scale study."

• "Lack of exercise + lack of sleep + junk food = immune aging, that's basically my lifestyle...."

On the other hand,

• "Starting endurance exercise at an old age is too high a hurdle"

• "Concerned about the strain on joints and the heart"

such concerns were also raised, and "how to continue at a suitable intensity" is being discussed as a realistic theme.

To sum up the atmosphere on social media in one phrase,

"I knew exercise was good, but seeing data at the immune cell level leaves fewer excuses"
, a somewhat uncomfortable yet convincing realization.

5. Veteran Athletes Controlled Inflammation Better than Younger Athletes

The Santélog article also touches on another study by the same research group.santelog.com

In that study,

• younger athletes

• and "veteran" athletes who have been training for many years

were compared in terms of immune response. They stimulated blood cells before and after intense exercise to observe changes in inflammatory markers like IL-6.

The results were surprising: younger athletes had a larger inflammatory response, while veterans controlled inflammation better.santelog.com

This can be interpreted as

"youth = strong reactions to everything"
but
"long-term training = efficient responses only when needed, without overreacting"

. **In immunity, what's important is not just "strength," but "controlled strength,"** as suggested here.

6. Immunity is Not Determined by Exercise Alone — Sleep, Diet, and Stress Also Matter

The research team identified factors affecting NK cells, including

• exercise habits and sedentary time

• obesity

• sleep quality

• diet

• vaccination

• stress

• use of immunosuppressive drugs

and overall lifestyle.santelog.com

In fact, the World Health Organization (WHO) recommends "at least 150 minutes of moderate-intensity physical activity or 75 minutes of vigorous activity per week" for adults, while reporting that about 31% of adults worldwide do not meet this standard.World Health Organization

In other words,

the moment you decide to exercise for immunity
, you already have a chance to be in the "top 70%" of the world

.

7. "So What and How Much Should I Do?" A Practical Answer

So, how much exercise should you aim for?
Summarizing WHO and various national guidelines, for healthy adults:World Health Organization

• 150-300 minutes of moderate-intensity aerobic exercise per week

  • Examples: brisk walking, slow jogging, cycling, leisurely swimming

• or 75-150 minutes of vigorous exercise per week

  • Examples: running, interval training

• + muscle-strengthening activities on 2 or more days a week

The "endurance training" highlighted in this study can be seen as a long-term continuation of this aerobic exercise component.

Of course,

• if you have chronic illnesses

• concerns about joints, heart, or blood vessels

• or have not exercised much for years

it's essential to consult with a doctor or specialist and start at an intensity that suits you.

8. Three Steps to Start an "Immunity-Friendly Exercise Habit" Today

Based on the research findings, here are three practical tips to start easily.

① First, "Break Up Sedentary Time"

• Stand up every 30-60 minutes and walk for 1-2 minutes

• Use the stairs for 1