Study on the effect of baths on inflammation and metabolism

The acute inflammatory responses triggered by regular exercise are thought to improve the inflammatory profile and insulin sensitivity. Since body temperature elevations partially mediate this response, passive heating may be a viable means of improving the inflammatory profile. This study by S. P. Hoekstra et al. investigated the acute and chronic effects of warm water immersion on inflammatory and metabolic markers.

Ten overweight men were immersed in water at 39°C (WWI) for 1 hour or left to rest at room temperature (RT) for 1 hour. Venous blood was drawn before the session, immediately after the session, and 2 hours after the session to determine mononuclear cellular expression of heat shock protein-72 (iHsp72) and plasma concentrations of extracellular Hsp72 (eHsp72), interleukin-6 (IL-6), fasting blood glucose, insulin, and nitrite. The participants then underwent a 2-week intervention with 10 WWI sessions (INT). Eight participants were included as a control group (CON).

Plasma concentrations of IL-6 and nitrite were significantly higher after the WWI session than after the RT session, while iHsp72 expression remained unchanged. Compared to resting levels, fasting blood glucose, insulin and eHsp72 concentrations decreased significantly after the chronic intervention, while no changes in iHsp72 expression were observed.

WWI induces an acute inflammatory response and increases nitrite bioavailability. The reductions in fasting blood glucose and insulin concentrations after the chronic intervention suggest that warm water immersion may serve as a means to improve glucose metabolism.

A single WWI session leads to an acute increase in plasma concentrations of interleukin-6 and nitrite, but not to an acute increase in heat shock protein 72 expression in mononuclear cells (iHsp72). Chronic WWI intervention lowers fasting blood glucose and insulin concentrations without changes in resting iHsp72 expression. Therefore, WWI shows potential as a strategy to combat chronic low-grade inflammation and improve glucose metabolism in individuals who are unable to access exercise due to lack of physical capacity.