Exercise immunology: The compelling link between physical activity and the body’s defense system

Highlights
This review has highlighted the following key points regarding exercise immunology:

• Acute exercise is an immune system adjuvant that improves defense activity and metabolic health.
• Data support a clear inverse relationship between moderate exercise training and illness risk.
• Exercise training has an anti-inflammatory influence mediated through multiple pathways.
• Illness risk is increased in athletes during periods of intensified training and competition.
• Increased carbohydrate and polyphenol intake is an effective nutritional strategy for immune support.
• Habitual exercise improves immune regulation, delaying the onset of age-related dysfunction.
• Advances in mass spectrometry technology will provide new insights on exercise–immune responses.

Abstract
This review summarises research discoveries within 4 areas of exercise immunology that have received the most attention from investigators:

1. 1. acute and chronic effects of exercise on the immune system,
   2. clinical benefits of the exercise–immune relationship,
   3. nutritional influences on the immune response to exercise, and;
   4. the effect of exercise on immunosenescence.

These scientific discoveries can be organised into distinctive time periods: 1900–1979, which focused on exercise-induced changes in basic immune cell counts and function; 1980–1989, during which seminal papers were published with evidence that heavy exertion was associated with transient immune dysfunction, elevated inflammatory biomarkers, and increased risk of upper respiratory tract infections; 1990–2009, when additional focus areas were added to the field of exercise immunology including the interactive effect of nutrition, effects on the ageing immune system, and inflammatory cytokines; and 2010 to the present, when technological advances in mass spectrometry allowed system biology approaches (i.e., metabolomics, proteomics, lipidomics, and microbiome characterisation) to be applied to exercise immunology studies.

The future will take advantage of these technologies to provide new insights on the interactions between exercise, nutrition, and immune function, with application down to the personalised level. Additionally, these methodologies will improve mechanistic understanding of how exercise-induced immune perturbations reduce the risk of common chronic diseases.

DOI: https://doi.org/10.1016/j.jshs.2018.09.009