Pro- and Anti-Inflammatory Effects of Acute and Chronic Exercise

Table of Contents

1. Why Exercise – From Energy to Immunity
2. The Cytokine Response to Exercise – Exerkines Revisited
3. The Diet, Activity and Inflammation Axis
4. The Biphasic Immune Cell Response to Acute Dynamic Exercise
5. Regular Exercise and NK Cell Biology
6. Clinical Synthesis – Exercise as an Anti-Inflammatory Intervention

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1 Why Exercise – From Energy to Immunity

The Two Faces of Exercise

A single bout of exercise produces two coupled physiological responses:

1. A metabolic / energy response — fuel mobilisation, glucose uptake, mitochondrial activation.
2. An immune / inflammatory response — cytokine release, immune-cell redistribution, modulation of inflammatory tone.

These two responses share many of the same mediators — IL-6 most prominently — but operate on overlapping rather than identical timescales. The clinical claim that exercise is anti-inflammatory refers primarily to chronic exercise and to the integrated effect over weeks and months; the acute bout is, paradoxically, often transiently pro-inflammatory [3].

The Three Categories of Exerkine

Exerkines released in response to exercise can be grouped by source tissue [1, 2]:

• Myokines — secreted by contracting skeletal muscle (IL-6, IL-15, irisin, BDNF).
• Adipokines — secreted by adipose tissue (adiponectin, leptin, FGF21).
• Hepatokines — secreted by the liver (FGF21, GDF15, ANGPTL4, follistatin).

Together they form a coordinated inter-organ messaging system (cf. Lecture 12) that translates muscle contraction into systemic immunometabolic effects.

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2 The Cytokine Response to Exercise – Exerkines Revisited

The IL-6 Signal

Building on Lecture 3: muscle-derived IL-6 functions as an energy allocator with three sequential effects [2]:

1. Energy sensing — signal that intramuscular energy stores are depleted.
2. Energy liberation — upregulation of lipolysis and gluconeogenesis.
3. Energy allocation — increased insulin receptor sensitivity, GLUT4 expression and short-chain fatty acid transporter expression in target tissues.

Critically, this exercise-induced IL-6 surge is largely independent of TNF-α — distinguishing it from infection-driven IL-6 [1, 3]. Without the TNF-α anchor, the downstream signalling cascade in the liver, adipose tissue and gut leans toward metabolic adaptation rather than acute-phase inflammation.

The Cytokine Cascade in Time

Time after exercise onset	Dominant signal	Functional role
0–30 min	Catecholamines, glucagon	Fuel mobilisation, demargination of immune cells
30–120 min	Myokine IL-6 (rises 10–100 fold in prolonged exercise)	Energy allocation, anti-inflammatory priming
1–4 h post	IL-10, IL-1Ra (rise after IL-6)	Anti-inflammatory dampening
2–24 h post	Cortisol (early peak, then decline)	Immunosuppressive, redistributive
24–72 h post	Adipokine/hepatokine shifts	Tissue-level metabolic adaptation

Table 1. Approximate kinetic sequence of exerkines and immune mediators after a single bout of endurance exercise (synthesised from [1–3]).

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3 The Diet, Activity and Inflammation Axis

The Integrative Picture

Gleeson and colleagues [3] mapped the anti-inflammatory effects of exercise and their interactions with diet. The framework integrates four mechanisms:

1. Reduction in visceral adiposity — the dominant source of chronic low-grade inflammation in industrialised populations.
2. Increase in adiponectin and decrease in leptin — restoring adipokine balance.
3. Decrease in pro-inflammatory monocyte traffic and a shift to anti-inflammatory macrophage phenotypes (M2 polarisation).
4. Acute IL-6 surges with downstream IL-10 / IL-1Ra induction — repeated cycles condition a more anti-inflammatory baseline.

Reduction in Visceral Adiposity

This is the single most important mediator of exercise’s anti-inflammatory effect in obesity and prediabetes. Visceral fat secretes a pro-inflammatory cytokine profile (Lecture 5); reducing visceral fat reduces this background tone.

Diet–Exercise Interactions

Diet and exercise act additively and sometimes synergistically:

• High-fibre, plant-based dietary patterns lower CRP and inflammatory markers independently of exercise.
• Caloric restriction alone reduces inflammation primarily through fat mass reduction.
• Combined approaches — modest caloric deficit, structured exercise, increased fibre and unsaturated fat intake — produce the strongest effects on chronic inflammation [3].

Practical insight. Exercise prescription that neglects nutritional counselling captures only part of the available anti-inflammatory effect. The two should be prescribed together.

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4 The Biphasic Immune Cell Response to Acute Dynamic Exercise

The Phenomenon

A single bout of moderate-to-vigorous dynamic exercise produces a stereotyped two-phase immune cell response [3, 4]:

1. Early lymphocytosis (peri-exercise) — circulating lymphocyte counts rise within minutes, driven primarily by β2-adrenergic catecholamine signalling. NK cells and CD8⁺ T cells are mobilised most strongly.
2. Lymphopenia (post-exercise) — within 1–2 hours after the bout, lymphocyte counts fall below pre-exercise baseline as cells are redistributed to peripheral tissues. The fall is largest after prolonged or intense exercise.

The pattern is well-established and reproducible across modalities (cycling, running, rowing) and ages.

Mechanisms

The peri-exercise lymphocytosis is driven by:

• Catecholamine release (epinephrine, norepinephrine) acting on β2-adrenergic receptors expressed by lymphocytes — particularly NK cells.
• Mobilisation from the marginated pool in capillary beds (lungs, spleen, marrow).
• Shear-stress-mediated detachment from endothelial surfaces.

The post-exercise lymphopenia reflects:

• Trafficking to peripheral tissues (lungs, gut, lymph nodes, possibly tumour beds).
• Apoptosis of a small subpopulation of activated effector cells.
• Cortisol-driven redistribution that peaks 1–2 hours post-exercise.

Why Biphasic Matters

The biphasic pattern is not pathology — it is a physiological surveillance routine. Acute exercise temporarily redistributes immune cells through a pattern that increases tissue sampling. Repeated cycles over weeks and months produce immunological “training” effects including improved NK-cell function and reduced immunosenescence in older adults (Section 5).

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5 Regular Exercise and NK Cell Biology

NK Cells as the Exercise-Sensitive Lymphocyte

Natural killer (NK) cells are the most β2-adrenergic-responsive lymphocyte subset. They show:

• the largest acute mobilisation during exercise,
• the steepest post-exercise drop, and
• the clearest chronic adaptation in regular exercisers (higher resting numbers, improved cytotoxicity per cell) [3].

Implications for Disease

The NK-cell response framework underwrites the epidemiological signal that regular moderate exercise reduces incidence of upper respiratory tract infections (the J-curve, Lecture 8 of the exercise-immunology lecture series), and contributes to the anti-cancer effects of physical activity:

• Acute exercise increases NK-cell circulation and tissue trafficking.
• Mobilised NK cells can infiltrate tumour beds and reduce tumour growth in animal models.
• Long-term regular exercise reshapes the NK-cell pool toward more effective cytotoxic phenotypes.

The same logic extends to other innate-immune populations: γδ T cells and certain monocyte subsets respond similarly to exercise.

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6 Clinical Synthesis – Exercise as an Anti-Inflammatory Intervention

Take-Home Principles

1. Acute exercise is transiently pro-inflammatory but anti-inflammatory in net effect once the cascade is integrated through 24–48 hours.
2. Chronic exercise reduces baseline CRP, TNF-α and IL-6 (in pro-inflammatory mode) primarily by reducing visceral adiposity and reshaping immune-cell phenotypes.
3. The dose matters: light activity has limited anti-inflammatory effect; moderate-to-vigorous regular activity produces the strongest signal; extreme overtraining can shift the balance toward pro-inflammatory states.
4. Diet and exercise are coupled: prescribe them together.
5. Sleep, addressed in Lecture 2, modulates the same axis and should not be neglected.

Clinical Pathways Forward

• Lecture 9 (MAFLD) applies the anti-inflammatory framework to liver disease.
• Lecture 10 (IBD) examines a disease in which the immune system is dysregulated and exercise must be carefully dosed.
• Lecture 11 translates these principles into staged exercise prescriptions for IBD remission and acute flares.
• Lecture 12 synthesises the inter-organ exerkine network.

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References

• [1] Pedersen BK, Febbraio MA. Muscle as an endocrine organ: focus on muscle-derived interleukin-6. Physiological Reviews. 2008;88(4):1379–1406.
• [2] Kistner TM, Pedersen BK, Lieberman DE. Interleukin 6 as an energy allocator in muscle tissue. Nature Metabolism. 2022;4(2):170–179.
• [3] Gleeson M, Bishop NC, Stensel DJ, Lindley MR, Mastana SS, Nimmo MA. The anti-inflammatory effects of exercise: mechanisms and implications for the prevention and treatment of disease. Nature Reviews Immunology. 2011;11(9):607–615. doi:10.1038/nri3041.
• [4] Walsh NP, Gleeson M, Shephard RJ, Gleeson M, Woods JA, Bishop NC, Fleshner M, Green C, Pedersen BK, Hoffman-Goetz L, Rogers CJ, Northoff H, Abbasi A, Simon P. Position statement. Part one: Immune function and exercise. Exercise Immunology Review. 2011;17:6–63.
• [5] Nieman DC, Wentz LM. The compelling link between physical activity and the body’s defense system. Journal of Sport and Health Science. 2019;8(3):201–217.
• [6] Pedersen BK. Anti-inflammatory effects of exercise: role in diabetes and cardiovascular disease. European Journal of Clinical Investigation. 2017;47(8):600–611.
• [7] Chow LS, et al. Exerkines in health, resilience and disease. Nature Reviews Endocrinology. 2022;18:273–289.

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One-Minute-Paper Topics

1. Distinguish the metabolic / energy response from the immune / inflammatory response to a single bout of exercise. Which shared mediator links them?
2. Why is chronic exercise anti-inflammatory while acute exercise can be transiently pro-inflammatory? Use the biphasic immune-cell response in your answer.
3. List the three categories of exerkine and one representative molecule from each.
4. Reproduce Table 1: the time-course of mediators 0–72 hours after exercise.
5. Why is exercise-induced IL-6 release “TNF-α independent”? What does this distinction mean for the downstream cascade?
6. Describe the four-mechanism Gleeson framework for the anti-inflammatory effects of exercise.
7. Why is visceral adiposity reduction the single most important mediator of exercise’s anti-inflammatory effect in obesity?
8. Diet and exercise act additively on chronic inflammation. Provide two examples of synergistic combinations.
9. Sketch the biphasic immune cell response: what rises within minutes, what falls within hours, and what is the net effect over 24–48 hours?
10. Which lymphocyte subset shows the largest acute response to exercise, and through which receptor system?
11. Why is the post-exercise lymphopenia not properly described as “immune suppression”? What is the alternative interpretation?
12. Describe two mechanisms by which catecholamines mobilise NK cells from the marginated pool.
13. How does cortisol contribute to the post-exercise lymphocyte redistribution? What is the typical kinetic of the cortisol response?
14. Why are NK cells central to the anti-cancer effects of regular exercise? Provide a mechanistic chain.
15. Outline two findings that support the J-curve of upper respiratory tract infection risk in regular exercisers.
16. Distinguish NK cell number from NK cell cytotoxicity per cell. Which adapts more strongly to regular training?
17. How would you design a clinical trial to test whether 12 weeks of moderate aerobic training reduces high-sensitivity CRP in patients with prediabetes?
18. Apply the framework to a patient with type 2 diabetes and chronic low-grade inflammation: list the three highest-yield levers from this lecture.
19. Why is overtraining a counter-example to “exercise is anti-inflammatory”? What does it tell us about dose-response?
20. Synthesise Lectures 3, 7 and 8 in a 5-line model of how regular exercise reduces cardiometabolic risk through coupled metabolic and immune mechanisms.