title: Heat stress and cardiovascular, hormonal, and heat shock proteins in humans.
abstract: BACKGROUND
  Conditions such as osteoarthritis, obesity, and spinal cord injury limit the ability of patients to exercise, preventing them from experiencing many well-documented physiologic stressors. Recent evidence indicates that some of these stressors might derive from exercise-induced body temperature increases.
  
  
  OBJECTIVE
  To determine whether whole-body heat stress without exercise triggers cardiovascular, hormonal, and extracellular protein responses of exercise.
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Twenty-five young, healthy adults (13 men, 12 women; age = 22.1 ± 2.4 years, height = 175.2 ± 11.6 cm, mass = 69.4 ± 14.8 kg, body mass index = 22.6 ± 4.0) volunteered.
  
  
  METHODS
  Participants sat in a heat stress chamber with heat (73°C) and without heat (26°C) stress for 30 minutes on separate days. We obtained blood samples from a subset of 13 participants (7 men, 6 women) before and after exposure to heat stress.
  
  
  METHODS
  Extracellular heat shock protein (HSP72) and catecholamine plasma concentration, heart rate, blood pressure, and heat perception.
  
  
  RESULTS
  After 30 minutes of heat stress, body temperature measured via rectal sensor increased by 0.8°C. Heart rate increased linearly to 131.4 ± 22.4 beats per minute (F₆,₂₄ = 186, P < .001) and systolic and diastolic blood pressure decreased by 16 mm Hg (F₆,₂₄ = 10.1, P < .001) and 5 mm Hg (F₆,₂₄ = 5.4, P < .001), respectively. Norepinephrine (F₁,₁₂ = 12.1, P = .004) and prolactin (F₁,₁₂ = 30.2, P < .001) increased in the plasma (58% and 285%, respectively) (P < .05). The HSP72 (F₁,₁₂ = 44.7, P < .001) level increased with heat stress by 48.7% ± 53.9%. No cardiovascular or blood variables showed changes during the control trials (quiet sitting in the heat chamber with no heat stress), resulting in differences between heat and control trials.
  
  
  CONCLUSIONS
  We found that whole-body heat stress triggers some of the physiologic responses observed with exercise. Future studies are necessary to investigate whether carefully prescribed heat stress constitutes a method to augment or supplement exercise.
authors.affiliation: Physical Therapy and Rehabilitation Science Department, University of Iowa, Iowa City, USA.
authors.forename: Masaki
authors.initials: M
authors.lastname: Iguchi
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Littmann
authors.forename: Shuo-Hsiu
authors.initials: SH
authors.lastname: Chang
authors.forename: Lydia A
authors.initials: LA
authors.lastname: Wester
authors.forename: Jane S
authors.initials: JS
authors.lastname: Knipper
authors.forename: Richard K
authors.initials: RK
authors.lastname: Shields
mesh_terms: D001794:Blood Pressure; D001831:Body Temperature; D004837:Epinephrine / Q000097:blood; D015444:Exercise; D005260:Female; D050884:HSP72 Heat-Shock Proteins / Q000096:biosynthesis / Q000097:blood*; D006339:Heart Rate; D018869:Heat-Shock Response; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010146:Pain; D011388:Prolactin / Q000097:blood; D055815:Young Adult
chemical_list: D050884:HSP72 Heat-Shock Proteins; D011388:Prolactin; D009638:Norepinephrine; D004837:Epinephrine