Elevating body termperature to reduce low-grade inflammation: a welcome strategy for those unable to exercise?

Chronic low-grade inflammation is increasingly recognized in the aetiology of a range of chronic diseases, including type 2 diabetes mellitus and cardiovascular disease, and may therefore serve as a promising target in their prevention or treatment. An acute inflammatory response can be induced by exercise; this is characterised by the acute increase in proinflammatory markers that subsequently stimulate the production of anti-inflammatory proteins. This may help explain the reduction in basal concentrations of pro-inflammatory markers following chronic exercise training. For sedentary populations, such as people with a disability, wheelchair users, or the elderly, the prevalence of chronic low-grade inflammation- related disease is further increased above that of individuals with a greater capacity to be physically active. Performing regular exercise with its proposed anti-inflammatory potential may not be feasible for these individuals due to a low physical capacity or other barriers to exercise. Therefore, alternatives to exercise that induce a transient acute inflammatory response may benefit their health. Manipulating body temperature may be such an alternative. Indeed, exercising in the heat results in a larger acute increase in inflammatory markers such as interleukin-6 and heat shock protein 72 when compared with exercising in thermoneutral conditions. Moreover, similar to exercise, passive elevation of body temperature can induce acute increases and chronic reductions in inflammatory markers and positively affect markers of glycaemic control. Here we discuss the potential benefits and mechanisms of active (i.e., exercise) and passive heating methods (e.g., hot water immersion, sauna therapy) to reduce chronic low-grade inflammation and improve metabolic health, with a focus on people who are restricted from being physically active.