Heat stress and cardiovascular, hormonal, and heat shock proteins in humans

J Athl Train. Mar-Apr 2012;47(2):184-90. doi: 10.4085/1062-6050-47.2.184.

Abstract

Context: 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.

Design: Randomized controlled trial.

Setting: University research laboratory.

Patients or other participants: 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.

Intervention(s): 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.

Main outcome measure(s): 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.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Blood Pressure
  • Body Temperature*
  • Epinephrine / blood
  • Exercise
  • Female
  • HSP72 Heat-Shock Proteins / biosynthesis
  • HSP72 Heat-Shock Proteins / blood*
  • Heart Rate
  • Heat-Shock Response*
  • Hot Temperature*
  • Humans
  • Male
  • Norepinephrine / blood
  • Pain
  • Prolactin / blood
  • Young Adult

Substances

  • HSP72 Heat-Shock Proteins
  • Prolactin
  • Norepinephrine
  • Epinephrine