Local cooling during hot water immersion improves perceptions without inhibiting the acute interleukin-6 response.

PURPOSE: Passive elevation of body temperature can induce an acute inflammatory response that has been proposed to be beneficial; however, it can be perceived as uncomfortable. Here, we investigate whether local cooling of the upper body during hot water immersion can improve perception without inhibiting the interleukin-6 (IL-6) response. METHODS: Nine healthy male participants (age: 22 ± 1 years, body mass: 83.4 ± 9.4 kg) were immersed up to the waist for three 60-min water immersion conditions: 42 °C hot water immersion (HWI), 42 °C HWI with simultaneous upper-body cooling using a fan (FAN), and 36 °C thermoneutral water immersion (CON). Blood samples to determine IL-6 plasma concentration were collected pre- and post-water immersion; basic affect and thermal comfort were assessed throughout the intervention. RESULTS: Plasma IL-6 concentration was higher for HWI and FAN when compared with CON (P < 0.01) and did not differ between HWI and FAN (P = 0.22; pre to post, HWI: 1.0 ± 0.6 to 1.5 ± 0.7 pg·ml-1, FAN: 0.7 ± 0.5 to 1.1 ± 0.5 pg·ml-1, CON: 0.5 ± 0.2 to 0.5 ± 0.2 pg·ml-1). At the end of immersion, basic affect was lowest for HWI (HWI: - 1.8 ± 2.0, FAN: 0.2 ± 1.6, CON 1.0 ± 2.1, P < 0.02); thermal comfort for HWI was in the uncomfortable range (3.0 ± 1.0, P < 0.01 when compared with FAN and CON), whereas FAN (0.7 ± 0.7) and CON (-0.2 ± 0.7) were in the comfortable range. CONCLUSION: Local cooling of the upper body during hot water immersion improves basic affect and thermal comfort without inhibiting the acute IL-6 response.

Ischaemic preconditioning improves upper-body endurance performance without altering V̇O2 kinetics.

PURPOSE: Whilst pre-exercise ischaemic preconditioning (IPC) can improve lower-body exercise performance, its impact on upper-limb performance has received little attention. This study examines the influence of IPC on upper-body exercise performance and oxygen uptake (V̇O2) kinetics. METHODS: Eleven recreationally-active males (24 ± 2 years) completed an arm-crank graded exercise test to exhaustion to determine the power outputs at the ventilatory thresholds (VT1 and VT2) and V̇O2peak (40.0 ± 7.4 ml·kg-1·min-1). Four main trials were conducted, two following IPC (4 × 5-min, 220 mmHg contralateral upper-limb occlusion), the other two following SHAM (4 × 5-min, 20 mmHg). The first two trials consisted of a 15-minute constant work rate and the last two time-to-exhaustion (TTE) arm-crank tests at the power equivalents of 95% VT1 (LOW) and VT2 (HIGH), respectively. Pulmonary V̇O2 kinetics, heart rate, blood-lactate concentration, and rating of perceived exertion were recorded throughout exercise. RESULTS: TTE during HIGH was longer following IPC than SHAM (459 ± 115 vs 395 ± 102 s, p = .004). Mean response time and change in V̇O2 between 2-min and end exercise (ΔV̇O2) were not different between IPC and SHAM for arm-cranking at both LOW (80.3 ± 19.0 vs 90.3 ± 23.5 s [p = .06], 457 ± 184 vs 443 ± 245 ml [p = .83]) and HIGH (96.6 ± 31.2 vs 92.1 ± 24.4 s [p = .65], 617 ± 321 vs 649 ± 230 ml [p = .74]). Heart rate, blood-lactate concentration, and rating of perceived exertion did not differ between conditions (all p ≥ .05). CONCLUSION: TTE was longer following IPC during upper-body exercise despite unchanged V̇O2 kinetics.HighlightsWhilst pre-exercise ischaemic preconditioning can improve lower-body exercise performance and alter V̇O2 kinetics, its impact on upper-limb performance has received little attention.An acute bout of ischaemic preconditioning prior to arm-crank ergometry exercise significantly improved time to exhaustion compared to a sham control condition.V̇O2 kinetics in response to ischaemic preconditioning remained unchanged, suggesting alternative mechanisms may explain performance improvements.

Acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults.

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.