There is no supplement, no drug, and no workout that produces the sustained catecholamine arc of deliberate cold exposure. That is not hyperbole — it is what the data consistently show. And when you pair cold with deliberate heat exposure, you unlock a hormetic combination that touches nearly every hormonal axis that matters: dopamine, norepinephrine, testosterone, growth hormone, and inflammatory markers.
Let us cut through the noise and build an actual protocol.
Cold Exposure: The Dopamine and Testosterone Case
The landmark study most people reference without reading is Srámek et al. (European Journal of Applied Physiology, 2000). Subjects immersed in 14 degrees Celsius water saw plasma norepinephrine increase by 530 percent and dopamine by 250 percent. These were not brief spikes — catecholamine levels remained elevated for hours after exposure.
As @hubermanlab has pointed out repeatedly on X, these catecholamine effects are “significant and long lasting (hours) and can be achieved with brief (1-3 min) exposure at very cold temperatures (35-45 degrees Fahrenheit) or long (30-60 min) exposure at more moderate (60 degrees Fahrenheit) temps.” The dose-response here gives you flexibility: you do not need a chest freezer at 34 degrees if you have a cold shower at 60 degrees — you just need more time.
On the testosterone front, the mechanism is still debated. Huberman noted in an October 2022 post that “there is still debate as to whether the increase in testosterone from cold exposure is due to rebound increase in blood flow or the cold itself.” A February 2023 reply from Huberman was more direct: “There are known increases in free and total testosterone in both men and women from regular deliberate cold exposure. Likely occurs as a stress compensation.”
The Tiina Mäkinen group (University of Oulu, 2008) showed that habitual winter swimmers had elevated baseline norepinephrine and reported improved stress tolerance, mood, and energy. A 2023 study published in Biology of Sport found that just five minutes of head-out cold water immersion at 20 degrees Celsius “elevated mood and reduced negative affect and changed resting state connectivity in brain networks associated with positive affect.”
The key insight: cold exposure is a hormonal reset button. It does not just briefly spike neurotransmitters — it appears to recalibrate baseline dopamine and norepinephrine tone with consistent practice.
The Cortisol Question
A persistent myth is that cold exposure jacks up cortisol, making it counterproductive for hormonal optimization. Huberman addressed this directly in a December 2025 post: “No evidence that deliberate cold exposure increases cortisol.” The acute stress response triggers adrenaline and noradrenaline, not the HPA axis cortisol cascade. This distinction matters enormously — you get the beneficial stress signaling without the catabolic hormone load.
However — and this is critical — Huberman also warned: “Do not do it after resistance training (it can prevent adaptations you want).” The Roberts et al. study (Journal of Physiology, 2015) demonstrated that cold water immersion post-resistance training blunted satellite cell activity and mTOR signaling, effectively attenuating hypertrophy gains. Cold showers are fine post-training; full immersion is not.
Heat Exposure: Growth Hormone, HSPs, and Inflammation
Sauna bathing is the other half of the hormesis equation, and the data here are arguably even stronger.
The Finnish KIHD cohort study (Laukkanen et al., JAMA Internal Medicine, 2015) followed over 2,300 men for 20 years and found that sauna use 4-7 times per week was associated with a 40 percent reduction in all-cause mortality compared to once-weekly use. As @foundmyfitness has highlighted, “Sauna bathing 4-7 times per week reduces dementia and Alzheimer’s disease risk by approximately 60 percent.”
The hormonal effects are potent. A single sauna session at 80 degrees Celsius for 20 minutes can increase growth hormone by 200-300 percent. Repeated sessions (two 20-minute rounds separated by a cooling period) have been shown to amplify this to 1,600 percent in some protocols (Leppäluoto et al., Journal of Clinical Endocrinology and Metabolism, 1986).
Heat shock proteins (HSPs) are the mechanistic bridge. As Dr. Rhonda Patrick (@foundmyfitness) noted, “The sauna robustly elevates heat shock protein levels that can persist for up to 48 hours.” HSP70 and HSP90 are molecular chaperones that prevent protein misfolding, reduce oxidative damage, and may directly protect Leydig cell function in the testes — the very cells that produce testosterone.
On inflammation, the data are clean: a 2018 study cited by @foundmyfitness showed that four weeks of sauna use increased IL-10 (anti-inflammatory) biomarkers, and sauna use is inversely associated with C-reactive protein levels. Lower systemic inflammation means a better hormonal environment across the board — less aromatase activity, better insulin sensitivity, improved SHBG regulation.
Huberman’s synthesis: “57 minutes of hot sauna per week and 11 minutes of cold exposure per week as reliable thresholds to derive major benefits on metabolism, insulin and growth hormone pathways.”
Post-Training Sauna: A Different Story Than Cold
While cold immersion post-resistance training is problematic, sauna after lifting may actually help. @fmfclips highlighted a study finding that “using the sauna after resistance training increases biomarkers of hypertrophy.” The mechanism likely involves increased blood flow, elevated HSP expression aiding muscle protein repair, and growth hormone amplification during the anabolic window. This is a small study that needs replication, but it aligns with the mechanistic logic.
The Protocol
Based on the aggregate evidence, here is a practical weekly template:
Cold exposure (11 or more minutes per week total):
- 3-4 sessions of 2-3 minutes each
- Temperature: uncomfortably cold but safe (50-59 degrees Fahrenheit for immersion, or cold shower at lowest setting)
- Timing: morning preferred (the dopamine surge sets your day), never within 4 hours after hypertrophy training
- Goal sensation: “I really want to get out but can stay in safely” (Huberman’s cue)
Heat exposure (57 or more minutes per week total):
- 3-4 sessions of 15-20 minutes each
- Temperature: 176-212 degrees Fahrenheit (traditional Finnish sauna range)
- Timing: post-resistance training is ideal; rest days work too
- For maximum GH response: do two rounds of 20 minutes separated by a 5-minute cool-down
Combined day example:
- Lift heavy (compound movements)
- Sauna 20 minutes post-training
- Cold plunge the following morning (never same session as lifting)
What to Track
This is where having data transforms anecdote into n-of-1 science. Key biomarkers to monitor when implementing a hormesis protocol:
- Total and free testosterone — monthly panels to catch trends
- SHBG — heat and cold both influence binding globulin dynamics
- CRP and IL-6 — inflammatory markers should trend down
- Fasting insulin and glucose — metabolic improvements are real and measurable
- Cortisol (AM) — confirm you are not inadvertently stressing the HPA axis
- IGF-1 — proxy for growth hormone activity
Kabal makes this tracking effortless — log your labs, tag your protocol changes, and watch the trends. Without data, you are guessing. With data, you are iterating.
The Bottom Line
Cold and heat are free. They require no prescription, no supplement stack, and no complicated periodization. The evidence base spans decades and thousands of subjects. The protocols are simple: 11 minutes of cold per week, 57 minutes of heat per week, timed correctly around training.
The mistake most people make is treating these as wellness theatre — a quick cold shower for the gram. The people getting results are the ones tracking their biomarkers, noting their protocol variables, and iterating based on data. That is what separates hormesis from hype.
Track your biomarkers with Kabal.