The acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults

Abstract

Regular exercise-induced acute inflammatory responses are suggested to improve the inflammatory profile and insulin sensitivity. As body temperature elevations partly mediate this response, passive heating might be a viable tool to improve the inflammatory profile. This study investigated the acute, and chronic effects of hot water immersion on inflammatory and metabolic markers. Ten sedentary, overweight males (BMI: 31.0±4.2 kg/m2) were immersed in water set at 39°C for 1 h (HWI) or rested for 1 h at ambient temperature (AMB). Venous blood was obtained prior to, immediately post and 2 h post-session for assessment of monocyte intracellular heat shock protein 72 (iHsp72) and plasma concentrations of extracelullar heat shock protein 72 (eHsp72), interleukin-6 (IL-6), fasting glucose, insulin and nitrite. Thereafter, participants underwent a 2-week intervention period, consisting of 10 hot water immersion sessions (INT). Eight BMI-matched participants (BMI: 30.0±2.5 kg/m2) were included as control (CON). Plasma IL-6 and nitrite concentrations were higher immediately following HWI compared to AMB (IL-6 p<0.001, HWI: 1.37±0.94 to 2.51±1.49 pg/ml; nitrite p=0.04, HWI: 271±52 to 391±72 nM), while iHsp72 expression was unchanged ( p=0.57). In contrast to resting iHsp72 expression ( p=0.59), fasting glucose ( p=0.04, INT: 4.44±0.93 to 3.98±0.98 mmol/l), insulin ( p=0.04, INT: 68.1±44.6 to 55.0±29.9 pmol/l) and eHsp72 ( p=0.03, INT: 17±41% reduction) concentrations were lowered after INT compared to CON. HWI induced an acute inflammatory response and increased nitric oxide bioavailability. The reductions in fasting glucose and insulin concentrations following the chronic intervention suggest that hot water immersion may serve as a tool to improve glucose metabolism