Too much of a good thing: Can high doses of exercise promote chronic low-grade inflammation and cardiovascular risk in competitive athletes?

Abstract

Regular engagement in moderate levels of exercise is associated with lower levels of inflammation and benefits cardiovascular and overall health outcomes. However, inflammation in response to exercise, like many natural phenomena, shows a biphasic response (acute elevation and typically more chronic improvement in inflammation) that is related to exercise dose, where dose encompasses exercise intensity, duration, and frequency. General training principles dictate that the optimal balanced exercise dose drives adaptations and performance benefits whilst also allowing for adequate recovery. As we review, whilst data are inconsistent, such balance may also minimise the risk of potentially inducing low-grade chronic inflammation. Beyond total exercise dose, other potential factors that may influence the development of low-grade chronic inflammation in competitive athletes include athlete demographics (in relation to sex, age, and experience), sport modality (endurance or contact sports), and other factors such as comorbid metabolic disorders, autoimmune conditions, and diet. Whilst competitive athletes in general have lower risk of cardiovascular disease, male masters' athletes exhibit more atherosclerosis, arrhythmias, and myocardial fibrosis than those who are more modestly active. Inflammation has been proposed as a possible mechanism driving the development of these cardiovascular conditions in athletes. Understanding the nuances of how exercise dose and athlete type influence the inflammatory response to exercise may help identify athletes vulnerable to developing these cardiovascular conditions.