The Role of Exercise in Reducing Inflammation
Researchers have amply documented the many benefits of exercise. Perhaps chief among these is exercise’s ability to protect people against all-cause mortality by preventing chronic diseases [1]. Given how chronic disease is the leading cause of death in the world, with cardiovascular disease, cancer, chronic lung disease, and diabetes mellitus accounting for the most deaths, the importance of regular physical conditioning should not be underestimated [1]. The mechanisms through which exercise prevents these diseases include improved stress resistance, decreased adiposity, and increased immune function [2]. This article will focus on how exercise reduces chronic inflammation and, in turn, offers protection against a mélange of chronic maladies [2].
Inflammation refers to the presence of macrophages in the body that, if found at high levels, can contribute to the development of autoimmune diseases and infections over the long term [2]. Chronic, low-grade inflammation describes a state in which circulating levels of cytokines and acute-phase proteins are two to four times higher than normal [2]. Individuals with chronic inflammation also contain slightly greater counts of neutrophils and natural killer cells in their bloodstreams [2]. This type of inflammation contributes to the development of multiple chronic diseases, including chronic obstructive pulmonary disease (COPD), Alzheimer’s disease, type 2 diabetes, and several cancers [2, 3]. Obesity and exacerbated aging are also linked to chronic, low-grade inflammation [2].
Exercise impacts inflammation levels by stimulating muscle fibers to produce interleukin-6 (IL-6), a cytokine with both pro- and anti-inflammatory benefits [1, 4]. Elevated concentrations of IL-6 result in increased levels of other anti-inflammatory cytokines, including IL-10 and IL-1ra [1]. IL-6 also enhances lipid turnover, which causes fat oxidation and lipolysis [1]. Additionally, IL-6 inhibits the production of TNF-α (tumor necrosis factor-alpha), a pro-inflammatory cytokine implicated in insulin resistance [4]. Regular physical conditioning harnesses the power of all these processes.
Recently, a study used an in-vitro tissue-engineered model of skeletal muscle to further elucidate the anti-inflammatory benefits of exercise [5]. The model, known as a myobundle, was electrically stimulated to mimic muscle contraction in order to study how exercise affects interferon-g (IFN-g)-induced muscle weakness [5]. In the cases of many inflammatory diseases, patients demonstrate elevated IFN-g levels [5]. When treated with IFN-g for seven days, myobundles demonstrate altered cytokine expression, notable myofiber disarray and atrophy, and reduced expression of calcium handling and contractile proteins [5]. Exercise prevents this decay. In the experiment, researchers found that electrical stimulation down-regulates the JAK (Janus kinase)/STAT 1 (signal transducer and activator of transcription 1) signaling pathway, preventing IFN-g myopathy [5]. This result demonstrates how STAT1 activation contributes to IFN-g inflammation, and how exercise can prevent that form of inflammation [5].
Given these anti-inflammatory mechanisms, exercise can significantly help individuals manage their pre-existing chronic diseases. A meta-analysis of 8,940 coronary heart patients found that aerobic exercise reduced patients’ cardiac mortality by 26% and all-cause mortality by 20% [4]. Patients also experienced reduced triglyceride levels, systolic blood pressure, and total cholesterol [4]. In a randomized trial consisting of 3,234 patients with impaired glucose tolerance, a regular exercise regimen combined with dietary changes reduced patients’ risk of type 2 diabetes by 58% [4]. Another study revealed the especially great benefits of combining resistance and aerobic exercise, as opposed to engaging in aerobic exercise alone, in reducing inflammation levels in patients with type 2 diabetes with the metabolic syndrome [6]. Not only is exercise effective in combating inflammation-associated chronic diseases, but the adoption of mixed training regimens can further elongate patients’ lives.
As much as researchers know about the anti-inflammatory benefits of exercise, there remains much more to be learned [5]. Regardless, the advantages are undeniable, making it an essential safeguard against the worldwide prevalence of chronic diseases.
References
[1] A. M. W. Petersen and B. K. Pedersen, “The anti-inflammatory effect of exercise,” Journal of Applied Physiology, vol. 98, no. 4, p. 1154-1162, p. 1-10, April 2005. [Online]. Available: https://doi.org/10.1152/japplphysiol.00164.2004.
[2] J. A. Woods, V. J. Vieira, and K. T. Keylock, “Exercise, Inflammation, and Innate Immunity,” Immunology and Allergy Clinics of North America, vol. 29, no. 2, p. 381-393, May 2009. [Online]. Available: https://doi.org/10.1016/j.iac.2009.02.011.
[3] J. van der Vlist and T. W. J. Janssen, “The Potential Anti-Inflammatory Effect of Exercise in Chronic Obstructive Pulmonary Disease,” Respiration, vol. 79, no. 2, p. 160-174, December 2009. [Online]. Available: https://doi.org/10.1159/000233264.
[4] B. K. Pedersen, “The anti-inflammatory effect of exercise: its role in diabetes and cardiovascular disease control,” Essays in Biochemistry, vol. 42, p. 105-117, November 2006. [Online]. Available: https://doi.org/10.1042/bse0420105.
[5] Z. Chen et al., “Exercise mimetics and JAK inhibition attenuate IFN-γ–induced wasting in engineered human skeletal muscle,” Science Advances, vol. 7, no. 4, p. 1-10, January 2021. [Online]. Available: https://doi.org/10.1126/sciadv.abd9502.
[6] S. Balducci et al., “Anti-inflammatory effect of exercise training in subjects with type 2 diabetes and the metabolic syndrome is dependent on exercise modalities and independent of weight loss,” Nutrition, Metabolism and Cardiovascular Diseases, vol. 20, no. 8, p. 608-617, October 2010. [Online]. Available: https://doi.org/10.1016/j.numecd.2009.04.015.