Inactivity affects immunity too
Inactivity usually brings the heart, the muscles or body weight to mind. The presentation’s framework adds immunity to that list. A meta-analysis reported that regular physical activity was linked to a 31% lower risk of community-acquired infection and a 37% lower risk of infection-related death. The picture in Türkiye is striking: 86.6% of people over 15 report no physical activity (Turkish Statistical Institute, TurkStat, 2025).
The other side of the picture is an aging population: people over 65 make up 11.1% of the total (about 9.6 million). The presentation’s main idea is this: regular, moderate-intensity exercise may reduce chronic inflammation (long-lasting, low-grade inflammatory activity), may lower the risk of upper respiratory tract infection and can strengthen the response to vaccines. That is why exercise stands out as a low-cost 'immune intervention'.
Reductions reported in studies
The values come from different designs and outcomes and should not be compared directly. Reverse causation and confounders cannot be ruled out.
Every workout is a wave of inflammation; the result is calm
After heavy exertion, some inflammatory messengers in the blood (cytokines), such as interleukin-6 (IL-6), rise temporarily. But the story does not end there: people who exercise regularly have lower inflammation at rest. In endurance athletes, resting CRP (C-reactive protein, a blood test that reflects inflammation) is usually below 0.5 mg/L, whereas in postmenopausal women with obesity it is 4 mg/L or higher. In large cohorts, active and fit people had lower markers; randomized studies (groups assigned by chance) were less consistent.
The muscle itself takes part, too. Contracting muscle releases signaling molecules called myokines, which is why muscle is seen as a kind of endocrine organ. IL-6 released as a myokine increases anti-inflammatory substances and supports fat burning. But intensity and duration matter: during a 30-minute brisk walk, IL-6 rises only from 1.3 to 2.0 pg/mL, while in a marathon it goes above 50 pg/mL. The presentation adds that this hypothesis may not hold at activity levels most middle-aged and older people can reach, and the evidence remains limited.
For immunity, dose matters: regular moderate-intensity movement is linked to lower infection risk, while very heavy training may push the risk back up.
Colds and the J-curve
For upper respiratory tract infections (URTI, such as the common cold), the presentation describes the 'J-curve': average risk in inactive people, lower risk with regular moderate exercise, and higher risk with marathons and heavy training. Because few people train this hard, the main public-health message is the lower risk linked to moderate exercise. Studies presented report lower URTI risk: 23% with regular moderate-to-high activity in a one-year observational study of 547 adults, and 43% fewer URTI days among 1,002 adults doing aerobic exercise at least 5 days a week.
The flip side is the 'open window' debate. The drop in blood lymphocytes (a type of white blood cell) after heavy exercise may not be suppression but a redistribution of cells to tissues such as the lungs and gut, and some URTIs reported in marathon runners may be airway irritation rather than infection. Even so, overtraining syndrome can bring fatigue, lower performance and immune suppression; training load, nutrient intake, recovery and sleep all contribute.
The aging immune system and vaccines
Two concepts come to the fore with age. Inflammaging is the chronic, low-level rise of IL-6, CRP and tumor necrosis factor-α (TNF-α). Immunosenescence is the decline of immune responses with age; as a result, vaccine responses may weaken and infections may become more severe. In three large cohorts (NHANES III, the Cardiovascular Health Study and Health ABC), physical activity was inversely related to these markers: the most active older adults had the lowest values. Intervention studies are inconsistent; those with higher baseline inflammation benefit more.
Observational and small studies on vaccine response are encouraging. Highly fit older adults showed a stronger antibody response to flu vaccination. In a 144-person study, after 10 months of aerobic training the protective antibody from the flu vaccine lasted 24 weeks. However, URTI frequency did not differ between the aerobic and flexibility groups, while illness severity and sleep disturbance were lower in the aerobic group. Reverse causation and confounders cannot be ruled out. In short, these findings point to exercise as a possible helper to the vaccine, not an alternative.
In practice: movement as part of a package
Exercise alone may not be enough. In the presentation’s example, if an older person with obesity adds 3 × 30 minutes of walking a week, a drop in inflammation is unlikely; weight loss, 30–60 minutes of activity a day, not smoking and plenty of vegetables and fruit are needed together. The infection-prevention package also includes adequate sleep (lack of sleep reduces vaccine response), stress management, a diet rich in vegetables and fruit, hygiene measures such as handwashing and ventilation, and vaccination.
How much movement? According to the World Health Organization (WHO) 2020 guideline, 150–300 minutes of moderate or 75–150 minutes of vigorous activity per week are recommended. Over 65, this is joined by muscle-strengthening on at least 2 days and balance exercises on at least 3 days a week. Even a small amount helps an inactive person; increase gradually, as effects may take months to show. People with chronic conditions, or those wondering about their vaccination schedule, should talk the plan over with their physician.
Further reading
- Rippe JM (ed.). Lifestyle Medicine, 3rd edition; Chapters 43, 44, 46
- WHO. Guidelines on Physical Activity and Sedentary Behaviour, 2020
- Nieman DC et al. Br J Sports Med 2011
- Campbell JP, Turner JE. Front Immunol 2018
- Sallis R et al. Br J Sports Med 2021 (COVID-19)
Sources
- Effects of Regular Physical Activity on the Immune System, Vaccination and Risk of Community-Acquired Infectious Disease in the General Population: Systematic Review and Meta-Analysis Chastin SFM ve ark., Sports Med 2021;51(8):1673–1686
- Upper respiratory tract infection is reduced in physically fit and active adults Nieman DC ve ark., Br J Sports Med 2011;45(12):987–992
- Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan Campbell JP, Turner JE, Front Immunol 2018;9:648
- Physical inactivity is associated with a higher risk for severe COVID-19 outcomes: a study in 48 440 adult patients Sallis R ve ark., Br J Sports Med 2021;55(19):1099–1105
- World Health Organization 2020 guidelines on physical activity and sedentary behaviour Bull FC ve ark., Br J Sports Med 2020;54(24):1451–1462
Last updated: October 2026