Heat stress and cardiovascular, hormonal, and heat shock proteins in humans.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 22488284 · doi:10.4085/1062-6050-47.2.184
What was done
Twenty-five healthy young adults (13 men, 12 women; mean age 22.1 ± 2.4 years) participated in a randomized trial comparing two 30-minute seated sessions on separate days: heat stress in a chamber at 73°C versus a control condition at 26°C. Rectal temperature, heart rate, blood pressure, and heat perception were measured across all participants. Blood samples were collected before and after exposure in a subset of 13 participants (7 men, 6 women) to measure plasma extracellular heat shock protein 72 (HSP72), norepinephrine, and prolactin.
What was found
Thirty minutes of heat stress increased core temperature by 0.8°C and increased heart rate linearly to 131.4 ± 22.4 beats per minute (P < .001). Systolic and diastolic blood pressure decreased by 16 mm Hg (P < .001) and 5 mm Hg (P < .001), respectively. In the blood biomarker subset (n = 13), heat stress increased plasma norepinephrine by 58% (P = .004), prolactin by 285% (P < .001), and HSP72 by 48.7% ± 53.9% (P < .001). No significant cardiovascular or blood biomarker changes occurred during the control condition.
Why it matters
This study demonstrates that passive whole-body heat stress acutely mimics several cardiovascular, neuroendocrine, and cellular stress responses typical of exercise. It provides physiological groundwork for investigating heat therapy as an exercise alternative or supplement in populations with physical limitations.
Limits
The study evaluated only the acute effects of a single 30-minute exposure. The sample was small (n = 25 overall, with blood biomarkers analyzed in only 13 participants) and restricted to young, healthy individuals, preventing direct generalization to clinical populations. Long-term clinical benefits and safety were not assessed.
Cited by
- supports Sitting in a 163°F sauna for 30 minutes increases heat shock proteins by 50% over baseline.