title: The impact of submaximal exercise during heat and/or hypoxia on the cardiovascular and monocyte HSP72 responses to subsequent (post 24 h) exercise in hypoxia.
abstract: BACKGROUND
  The aims of this study were to describe the cellular stress response to prolonged endurance exercise in acute heat, hypoxia and the combination of heat and hypoxia and to determine whether prior acute exposure to these stressors improved cellular tolerance to a subsequent exercise bout in hypoxia 24 h later.
  
  
  METHODS
  Twelve males (age 22 ± 4 years, height 1.77 ± 0.05 m, mass 79 ± 12.9 kg, VO2 max 3.57 ± 0.7 L · min(-1)) completed four trials (30-min rest, 90-min cycling at 50% normoxic VO2 max) in normothermic normoxia (NORM; 18°C, FIO2 = 0.21), heat (HEAT; 40°C, 20% RH), hypoxia (HYP; FIO2 = 0.14) or a combination of heat and hypoxia (COM; 40°C, 20% RH, FIO2 = 0.14) separated by at least 7 days. Twenty-four hours after each trial, participants completed a hypoxic stress test (HST; 15-min rest, 60-min cycling at 50% normoxic VO2 max, FIO2 = 0.14). Monocyte heat shock protein 72 (mHSP72) was assessed immediately before and after each exercise bout.
  
  
  RESULTS
  mHSP72 increased post exercise in NORM (107% ± 5.5%, p > 0.05), HYP (126% ± 16%, p < 0.01), HEAT (153% ± 14%, p < 0.01) and COM (161% ± 32%, p < 0.01). mHSP72 had returned to near-resting values 24 h after NORM (97% ± 8.6%) but was elevated after HEAT (130% ± 19%), HYP (118% ± 17%) and COM (131% ± 19%) (p < 0.05). mHSP72 increased from baseline after HSTNORM (118% ± 12%, p < 0.05), but did not increase further in HSTHEAT, HSTHYP and HSTCOM.
  
  
  CONCLUSIONS
  The prior induction of mHSP72 as a result of COM, HEAT and HYP attenuated further mHSP72 induction after HST and was indicative of conferred cellular tolerance.
authors.affiliation: Sport and Exercise Science Applied Research Group, Coventry University, Coventry, UK.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Lee
authors.affiliation: Inflammation and Infection Group, School of Science and Technology, University of Westminster, London, UK.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Emery-Sinclair
authors.affiliation: Inflammation and Infection Group, School of Science and Technology, University of Westminster, London, UK.
authors.forename: Richard Wa
authors.initials: RW
authors.lastname: Mackenzie
authors.affiliation: Sport and Exercise Science Applied Research Group, Coventry University, Coventry, UK.
authors.forename: Afthab
authors.initials: A
authors.lastname: Hussain
authors.affiliation: Department of Sport and Exercise Sciences, University of Bedfordshire, Bedford, UK.
authors.forename: Lee
authors.initials: L
authors.lastname: Taylor
authors.affiliation: Sport and Exercise Science Applied Research Group, Coventry University, Coventry, UK.
authors.forename: Rob S
authors.initials: RS
authors.lastname: James
authors.affiliation: Sport and Exercise Science Applied Research Group, Coventry University, Coventry, UK.
authors.forename: C Douglas
authors.initials: CD
authors.lastname: Thake
keywords: Cross-acclimation; Cycling; Humans; Preconditioning