Thermoregulation, Stress, and the Physiological Benefits of Sauna Use

Saunas are a tool. They can support longevity, improve quality of life, and enhance overall performance and recovery. But they are not a one dimensional solution. Because they influence multiple systems in the body, the way you use a sauna should depend on the outcome you’re trying to achieve.

We’ve read and consumed research across traditional literature, contemporary studies, and the work of leading scientists in the field. The protocols and supporting research are linked throughout this paper, with a full works cited section below.

This paper outlines how saunas work, the physiological processes they initiate, the protocols aligned with specific goals, and what actually holds up under scrutiny versus what does not. The objective is clarity: to help you use the sauna with intention and measurable results.

Basic Thermoregulation

The body regulates temperature through two distinct but interconnected zones: shell temperature and core temperature.

Shell temperature refers to the temperature of the skin and superficial tissues. It changes rapidly in response to the environment. Wind, humidity, water exposure, or air temperature can shift shell temperature within seconds.

Core temperature refers to the temperature of internal organs and deep tissues. Core temperature is tightly controlled because even small deviations can impair cellular function.

The primary control center for temperature regulation is the preoptic area (POA) of the hypothalamus. The POA continuously receives input from:

• Peripheral thermoreceptors in the skin (monitoring shell temperature)
• Central thermoreceptors in the spinal cord and brain (monitoring core temperature)

It integrates these signals and initiates appropriate responses to maintain stability.

When the skin detects heat, peripheral receptors send signals to the POA. The brain interprets this as a potential thermal threat and activates regulation.

Temperature change in the body is gradient-driven, meaning the environment influences the shell first, then the shell influences the core. Core temperature does not immediately rise simply because the surrounding air or water is hot. The body initially attempts to defend core stability.

This leads to a counterintuitive principle: heating is regulated through cooling. When the surface of the body warms, blood is redistributed from deeper tissues toward the skin. Sweating begins. These mechanisms are designed to dissipate heat and protect internal organs. Early in thermal exposure, core temperature may remain stable or shift minimally because cooling systems are fully active.

Only when external heat load exceeds the body’s ability to dissipate it does core temperature begin to rise in a sustained way. At that point, deeper physiological adaptations are triggered. The shell acts as the sensor and interface with the environment. The core is the protected center. The brain, through the POA, coordinates the exchange between the two.

What processes do thermoregulation activate?

Thermoregulation activates multiple bodily processes. In this paper we will explain the few important ones that create the desired outcomes of sauna use.

The first being the cooling processes

When the thermoreceptors in the skin and shell detect heat, the signal is transmitted to the hypothalamus, which starts the immediate cooling process. The physiological response is to:

• Increase plasma volume: improving the ability to circulate blood.
• Increase peripheral blood flow: allowing more internal heat to be transported from the core to the surface.
• Increase stroke volume: meaning the heart pumps more blood per beat, increasing the amount of warm blood delivered to the skin with each contraction.
• Increase heart rate: more beats per minute.
• Vasodilation: widening of blood vessels, particularly near the surface of the skin, which increases blood flow to peripheral tissues.
• Sweating: sweating cools by the release of fluid onto the skin’s surface. As this fluid evaporates, it removes heat from the body, lowering temperature.

The second is the release of Heat Shock Proteins, or sometimes known as (HSPs)

The basic understanding of HSPs is that they preserve a process called proteostasis. This means they assist and facilitate protein synthesis, folding, and degradation (the process of breaking down proteins into smaller peptides or amino acids).

Proteostasis is essential for these functions:

• Quality control. Misfolded or damaged proteins are eliminated before they grow/combine and disrupt cellular function.
• Regulation. Many proteins are degraded deliberately to control signaling pathways and timing of biological processes.
• Resource recycling. Amino acids released from degraded proteins are reused for new protein synthesis or metabolic pathways.

They are deployed in humans through a change in environment. This can be through a stress derived from heat, cold, UV, osmotic stress, or pH shifts.

Without HSPs, cells would accumulate misfolded and damaged proteins, leading to impaired cellular function, increased inflammation, and accelerated degeneration. Over time, this would reduce tissue resilience and compromise recovery capacity.

HSP activation includes:

• Enhanced cellular resilience
• Improved recovery from physical or environmental stress
• Contributions to longevity

The third is the release of Dynorphins

These are the opposite of endorphins. They upregulate during a stress response to make you feel worse, the panic you feel during a hard sauna session. They are there to get the body out of stressful situations.

They:

• Increase discomfort
• Increase alertness
• Increase focus
• Create a mild stress signal

However, downstream of dynorphin release is the increase in other receptors that bind to dopamine and endorphins. The pleasure pain balance in the body is skewed, so there is a natural production and release of endorphins, as well as an increased number of receptor sites.

Thus, dynorphins increase our baseline level of mood, and allow “good” events to be perceived as “great” ones.

Short-term dynorphin stress makes the dopamine system more responsive afterward:

• Improves stress tolerance
• Increases mental resilience
• Stabilizes mood response
• Reduces baseline inflammation

It’s not how saunas create heat that makes them so beneficial. It’s that they are the most efficient way to receive the heat necessary to make real effective change. In the studies that measured these processes in action and at maximum effectiveness, it was a range of 176 - 212 degrees fahrenheit that sparked these processes. If you think you need infrared, look at the basic scientific principles that make saunas effective and ask yourself, am I consistently hitting that heat range? If not, you are just getting warm.

Sauna use is effective because it forces the body to regulate heat through a coordinated stress response. The shell detects environmental heat first, the hypothalamus responds by activating cooling mechanisms, and the body works to protect core temperature through increased circulation, sweating, vasodilation, and cardiovascular output. When the heat load is strong enough, deeper adaptations occur, including heat shock protein activation and dynorphin-driven stress signaling. These processes support cellular repair, recovery, resilience, mood regulation, and improved tolerance to physical and environmental stress. The benefit of sauna use is not simply feeling warm; it comes from reaching a high enough thermal stimulus to activate the body’s full thermoregulatory and adaptive systems.

- Western Sol