Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan

Abstract

Epidemiological evidence indicates that regular physical activity and/or frequent structured exercise reduces the incidence of many chronic diseases in older age, including communicable diseases such as viral and bacterial infections, as well as non-communicable diseases such as cancer and chronic inflammatory disorders. Despite the apparent health benefits achieved by leading an active lifestyle, which imply that regular physical activity and frequent exercise enhance immune competency and regulation, the effect of a single bout of exercise on immune function remains a controversial topic. Indeed, to this day, it is perceived by many that a vigorous bout of exercise can temporarily suppress immune function. In the first part of this review, we deconstruct the key pillars which lay the foundation to this theory—referred to as the “open window” hypothesis—and highlight that: (i) limited reliable evidence exists to support the claim that vigorous exercise heightens risk of opportunistic infections; (ii) purported changes to mucosal immunity, namely salivary IgA levels, after exercise do not signpost a period of immune suppression; and (iii) the dramatic reductions to lymphocyte numbers and function 1–2 h after exercise reflects a transient and time-dependent redistribution of immune cells to peripheral tissues, resulting in a heightened state of immune surveillance and immune regulation, as opposed to immune suppression. In the second part of this review, we provide evidence that frequent exercise enhances—rather than suppresses—immune competency, and highlight key findings from human vaccination studies which show heightened responses to bacterial and viral antigens following bouts of exercise. Finally, in the third part of this review, we highlight that regular physical activity and frequent exercise might limit or delay aging of the immune system, providing further evidence that exercise is beneficial for immunological health. In summary, the over-arching aim of this review is to rebalance opinion over the perceived relationships between exercise and immune function. We emphasize that it is a misconception to label any form of acute exercise as immunosuppressive, and, instead, exercise most likely improves immune competency across the lifespan.

Cardiorespiratory fitness and incident lung and colorectal cancer in men and women: Results from the Henry Ford Exercise Testing (FIT) cohort

“…In addition, although it does not appear that there is a threshold effect in which higher CRF no longer reduces one's risk of lung or colon cancer or all‐cause mortality after either of these diagnoses, the nature of the current analysis (ie, categorical) precluded us from appropriately addressing this issue. The protective effect observed could be due to the positive effects of fitness, including improved respiratory function, decreased bowel transit time, better immune function, or reductions in systemic inflammation for example, which is an active area of research …”

“…The protective effect observed could be due to the positive effects of fitness, including improved respiratory function, decreased bowel transit time, better immune function, or reductions in systemic inflammation for example, which is an active area of research. 43,44 There are several strengths to the current study, including the large sample size, inclusive of men and women, with a large nonwhite race sample. However, there also are several limitations to note.…”

Definition and treatment of arrhythmogenic cardiomyopathy: an updated expert panel report

“…It remains unclear if myocarditis in AC is a primary phenomenon or reactive to spontaneous cardiomyocyte death. The hypothesis that a genetically vulnerable myocardium may predispose to myocarditis has been advanced and local myocardial production of selected cytokines and alterations in the balance between circulating pro‐inflammatory and anti‐inflammatory cytokines in patients with AC has been demonstrated . In one study, cytokines implicated in granulomatous inflammation promoted rapid intracellular translocation of junctional plakoglobin in cultured neonatal rat ventricular myocytes, suggesting that inflammatory mediators might play a role in AC, even in the absence of infiltrating inflammatory cells .…”

“…In one study, cytokines implicated in granulomatous inflammation promoted rapid intracellular translocation of junctional plakoglobin in cultured neonatal rat ventricular myocytes, suggesting that inflammatory mediators might play a role in AC, even in the absence of infiltrating inflammatory cells . Furthermore, the increasing understanding of the interplay between immune response and exercise might provide further insights in the mechanisms of exercise promoted disease progression in AC …”

Acute Illness in the Athlete

“…The literature supports both the positive and negative effects that exercise can have on immune function and risk of illness. [1][2][3] The risk of illness has been found to increase in situations of prolonged and/or intense training, especially in athletes who are already immunocompromised, have high levels of intrinsic or extrinsic stressors, or have had a recent infection. 4 However, most athletes training at a moderate level benefit from improved immune function and lower infection rates compared with people who do not exercise.…”