08/14/2026
YOUR SAUNA IS CHANGING YOUR BLOOD.
And it may be one of the most overlooked adaptations to regular heat exposure.
When you enter a sauna, your body does far more than sweat.
As body temperature rises, blood vessels in the skin dilate and skin blood flow increases to dissipate heat. Heart rate and cardiac output rise as your cardiovascular system works to maintain circulation and regulate temperature.
But with repeated heat exposure, something even more interesting can happen.
Your plasma volume can increase.
In one sauna based heat acclimation study, plasma volume increased by approximately 9%, compared with around 1% in the comparison condition.
Why does this matter?
Greater plasma volume can support stroke volume, skin blood flow, sweating and cardiovascular stability during heat stress.
Heat also increases blood flow through your vessels, creating shear stress, the force of flowing blood against the endothelium, the cellular lining of your blood vessels.
Repeated passive heating has been shown in human research to improve endothelial function, with studies also reporting improvements in arterial stiffness and blood pressure.
Sauna does not replace exercise.
But heat and exercise share several acute cardiovascular responses, including increased heart rate, cardiac output and blood flow.
So while you may think the most important thing happening in a sauna is sweat, your circulatory system is doing considerably more.
Your body isn't simply enduring the heat. It's adapting to it.
Studies referenced:
Stanley J et al. Sauna based heat acclimation and plasma volume.
Scoon GSM et al. J Sci Med Sport. 2007.
Brunt VE et al. J Physiol. 2016.
Périard JD et al. Physiol Rev. 2021.
Laukkanen JA et al. Mayo Clin Proc. 2018.
