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Brunt VE, Minson CT. Heat therapy: mechanistic underpinnings and applications to cardiovascular health. J Appl Physiol (1985) 2021; 130:1684-1704. [PMID: 33792402 DOI: 10.1152/japplphysiol.00141.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cardiovascular diseases (CVD) are the leading cause of death worldwide, and novel therapies are drastically needed to prevent or delay the onset of CVD to reduce the societal and healthcare burdens associated with these chronic diseases. One such therapy is "heat therapy," or chronic, repeated use of hot baths or saunas. Although using heat exposure to improve health is not a new concept, it has received renewed attention in recent years as a growing number of studies have demonstrated robust and widespread beneficial effects of heat therapy on cardiovascular health. Here, we review the existing literature, with particular focus on the molecular mechanisms that underscore the cardiovascular benefits of this practice.
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Affiliation(s)
- Vienna E Brunt
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado.,Department of Human Physiology, University of Oregon, Eugene, Oregon
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Hoekstra SP, Bishop NC, Faulkner SH, Bailey SJ, Leicht CA. Acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults. J Appl Physiol (1985) 2018; 125:2008-2018. [DOI: 10.1152/japplphysiol.00407.2018] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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 men [body mass index (BMI): 31.0 ± 4.2 kg/m2, mean ± SD] 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 before the session, immediately postsession, and 2 h postsession for assessment of monocyte intracellular heat shock protein-72 (iHsp72) and plasma concentrations of extracellular Hsp72 (eHsp72), interleukin-6 (IL-6), fasting glucose, insulin, and nitrite. Thereafter, participants underwent a 2-wk 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 with 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), whereas 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 with 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. NEW & NOTEWORTHY A single hot water immersion (HWI) session induces an acute increase in plasma interleukin-6 and nitrite concentrations but does not acutely elevate heat shock protein-72 expression in monocytes [intracellular Hsp72 (iHsp72)]. A chronic HWI intervention reduces fasting glucose and insulin concentrations in the absence of changes in resting iHsp72. Therefore, HWI shows potential as a strategy to combat chronic low-grade inflammation and improve glucose metabolism in individuals without the physical capacity to do so using exercise.
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Affiliation(s)
- S. P. Hoekstra
- The Peter Harrison Centre for Disability Sport, Loughborough University, Loughborough, United Kingdom
- The School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom
| | - N. C. Bishop
- The School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom
| | - S. H. Faulkner
- Department of Engineering, Nottingham Trent University, Nottingham, United Kingdom
| | - S. J. Bailey
- The School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom
| | - C. A. Leicht
- The Peter Harrison Centre for Disability Sport, Loughborough University, Loughborough, United Kingdom
- The School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom
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