title: Post-exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat.
abstract: We examined whether daily hot water immersion (HWI) after exercise in temperate conditions induces heat acclimation and improves endurance performance in temperate and hot conditions. Seventeen non-heat-acclimatized males performed a 6-day intervention involving a daily treadmill run for 40 min at 65% V̇O2max in temperate conditions (18 °C) followed immediately by either HWI (N = 10; 40 °C) or thermoneutral (CON, N = 7; 34 °C) immersion for 40 min. Before and after the 6-day intervention, participants performed a treadmill run for 40 min at 65% V̇O2max followed by a 5-km treadmill time trial (TT) in temperate (18 °C, 40% humidity) and hot (33 °C, 40% humidity) conditions. HWI induced heat acclimation demonstrated by lower resting rectal temperature (Tre , mean, -0.27 °C, P < 0.01), and final Tre during submaximal exercise in 18 °C (-0.28 °C, P < 0.01) and 33 °C (-0.36 °C, P < 0.01). Skin temperature, Tre at sweating onset and RPE were lower during submaximal exercise in 18 °C and 33 °C after 6 days in HWI (P < 0.05). Physiological strain and thermal sensation were also lower during submaximal exercise in 33 °C after 6 days in HWI (P < 0.05). HWI improved TT performance in 33 °C (4.9%, P < 0.01) but not in 18 °C. Thermoregulatory measures and performance did not change in CON. Hot water immersion after exercise on 6 days presents a simple, practical, and effective heat acclimation strategy to improve endurance performance in the heat.
authors.affiliation: College of Health and Behavioural Sciences, Bangor University, Bangor, Gwynedd, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Zurawlew
authors.affiliation: College of Health and Behavioural Sciences, Bangor University, Bangor, Gwynedd, UK.
authors.forename: N P
authors.initials: NP
authors.lastname: Walsh
authors.affiliation: College of Health and Behavioural Sciences, Bangor University, Bangor, Gwynedd, UK.
authors.forename: M B
authors.initials: MB
authors.lastname: Fortes
authors.affiliation: College of Health and Behavioural Sciences, Bangor University, Bangor, Gwynedd, UK.
authors.forename: C
authors.initials: C
authors.lastname: Potter
mesh_terms: D000064:Acclimatization; D000328:Adult; D054874:Athletic Performance; D001831:Body Temperature; D015444:Exercise; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D010807:Physical Endurance; D012881:Skin Temperature; D013546:Sweating; D013697:Thermosensing; D014867:Water; D055815:Young Adult
chemical_list: D014867:Water
keywords: heat illness; hot bath; hyperthermia; perfor-mance; running; thermoregulation