"Movement is the best medicine" – this phrase appears in traditions from ancient Greece to Far Eastern healing methods. Today, immunology confirms: those who engage in regular physical activity build a more robust defense system. Surprisingly, it's not the most intense training that offers the best protection, but rather wisely measured activity that allows for recovery. This is the high-performance formula for more energy, fewer infections, and a long, healthy life.

Our immune system is a dynamic network of cells, signaling molecules, and organs. Movement acts on it like a metronome. Moderate endurance training temporarily increases the circulation of immune cells, reduces chronic low-grade inflammation, and improves the function of natural killer cellsimmune cells that rapidly eliminate virus-infected and transformed cells. Strength training additionally stimulates myokinesinflammatory-modulating signaling molecules from muscle, which have anti-inflammatory effects. The dose is critical: too little activity promotes systemic inflammationpersistently elevated inflammatory signaling molecules in the blood, while too much without recovery can dampen immune function. High performers navigate in between: enough stimuli for adaptation, sufficient recovery for stability.

Inactivity weakens the defense. In older adults, enforced cessation of movement led to decreased fitness, increased fat mass, reduced muscle mass, and higher inflammatory markers such as interleukin-6 and C-reactive protein, while immune cells decreased; those who remained active showed the opposite – better body composition, lower inflammatory values, and more stable immune cell functions ^[1]. Breaking up long periods of sitting normalizes inflammatory profiles and improves vessel-related immune mechanisms, among other things through more favorable macrophage polarizationtransition from pro-inflammatory (M1) to anti-inflammatory (M2) ^[2]. Resistance training lowers pro-inflammatory cytokines (e.g., IL-6, TNF-α) and increases anti-inflammatory signals (IL-10), associated with better cardiovascular and autonomic parameters – a plus for resilience and infection defense in older age ^[3]. Conversely, a phase of highly intensified training without adequate recovery dampens parts of the immune response: lymphocytes and CD8+ T cells decline, and susceptibility to infections may increase ^{[4] [5]}. Intensive training becomes particularly risky during illnesses; animal data show that moderate exercise during an infection has positive effects, while exhaustion-inducing training tends to worsen symptoms and may increase mortality ^[6]. Finally, nutrition plays a central role: very intense phases of training without adequate nutrient intake can additionally weaken immune defense ^[7].

Three lines of research paint a consistent picture. First: aerobic activity of moderate intensity temporarily strengthens immune cell circulation and can have measurable effects in clinical contexts. In a randomized study with COVID-19 patients, a two-week moderate endurance program improved quality of life and increased leukocytes, lymphocytes, and immunoglobulin A – a marker of mucosal immunity ^[8]. Practically, this means: even short, measured interventions can measurably boost defense. Second: resistance training acts as a systemic inflammatory modulator. In older adults, 12 weeks of moderate strength training resulted in better hemodynamic and autonomic parameters and a shift in cytokine profile: less IL-6 and TNF-α, more IL-10 and Klotho – signatures associated with healthier immune balance and vascular function ^[3]. This explains why preserving muscle is an immunological investment for longevity. Third: dose and recovery matter. Meta-analyses on intensified training show decreases in certain lymphocyte populations and signs of immune dysregulation when stress and recovery are out of balance ^[4]; reviews among athletes describe increased infection symptoms and suppressed immune parameters under prolonged high loads without adequate recovery ^[5]. The mechanism is plausible: neuroendocrine dysregulation and pro-inflammatory shifts under chronic stress burden the defense. Together, a clear principle emerges: moderate and consistent beats extreme and exhausting – especially when long-term health and performance count.

- Plan for 150–300 minutes of moderate endurance training per week (e.g., brisk walking, cycling, light jogging); spread it over 4–6 sessions of 25–45 minutes each. Consistency is more important than achieving high intensity records ^[8].
- Integrate 2–3 strength training sessions weekly (full body, 6–10 exercises, 2–3 sets, 6–12 repetitions at 65–80% 1RM). Aim for major muscle groups, clean technique, and progressive yet moderate increases ^[3].
- Break up sitting times: stand up for 1–3 minutes every 30–60 minutes, take the stairs, mobilize. This micro-movement helps normalize inflammatory profiles ^[2].
- Prioritize recovery: 7–9 hours of sleep, at least 24–48 hours between intense sessions of the same muscle group, and a recovery week every 6–8 weeks. Use subjective markers like daily energy, sleep quality, and resting heart rate; symptom-based reduction prevents immune dips ^{[4] [5]}.
- Train when infected according to the "neck rule": No training for symptoms below the neck (fever, cough, muscle pain); gradually resume after symptoms subside. Avoid pushing to exhaustion during illness ^[6].
- Eat appropriately for training: adequate energy, 1.6–2.2 g protein/kg/day depending on goals, carbohydrates around intensive sessions, healthy fats, and micronutrients from whole foods. Avoid crash diets and extremely unbalanced macronutrient distributions to prevent immune compromises ^[7].

In the coming years, more precise biomarkers will define your personal "sweet spot" load for immune strength – from wearables to cytokine profiles. Until then, remember: dose wisely, move regularly, and recover adequately. This way, you link performance with protection – today and in the long term.