Improved neural control of body temperature following heat acclimation in humans.
Level 4 - case-series / case-control
Single-group pre-post physiological intervention study without a separate control group
PubMed 32011734 · doi:10.1113/JP279266
What was done
Fourteen healthy adults (9 men and 5 women, aged 27 ± 5 years) completed a 7-day heat acclimation protocol. Before and after acclimation, participants were exposed to passive heat stress. Investigators measured resting core temperature, skin sympathetic nerve activity (efferent signals driving thermoeffectors), cutaneous vasodilatation, and local and whole-body sweat production.
What was found
Following 7 days of heat acclimation: - Resting core temperature decreased by -0.29°C [95% CI: -0.40, -0.18; P < 0.01]. - Whole-body sweat rate increased by +0.54 L h^-1 [95% CI: 0.32, 0.75; P < 0.01]. - The change in mean body temperature required to activate skin sympathetic nerve activity decreased by -0.21°C [95% CI: -0.34, -0.08; P < 0.01]. - Activation thresholds were lowered for cutaneous vasodilatation [-0.18°C (95% CI: -0.35, -0.01); P = 0.04] and local sweat rate [-0.13°C (95% CI: -0.24, -0.01); P = 0.03].
Why it matters
This study provides direct neurophysiological evidence that heat acclimation shifts the central activation threshold of efferent sympathetic outflow to the skin, triggering earlier heat dissipation via sweating and vasodilation.
Limits
The study was small (n = 14) and limited to young, healthy adults. It used an uncontrolled before-and-after design without a parallel sham or time-control group, and evaluated heat adaptation exclusively under passive heat stress rather than active exercise conditions.
Cited by
- supports Repeated heat exposure causes heat acclimation, prompting the body to begin sweating at a lower core body temperature threshold.