Dr. Rhonda Patrick is making a bold argument here: sauna use isn't just recovery. It's training. Specifically, she's positioning heat acclimation as a way to get many of the performance benefits associated with IGF-1 and growth hormone — more endurance, more muscle, sharper cognition — without the risks that come from actually elevating those hormones to supraphysiological levels through therapy. That's a nuanced and important distinction, and it's one that doesn't get nearly enough attention.
The numbers she cites are striking. A 32% increase in running endurance from two 30-minute sauna sessions per week. A 16-fold spike in growth hormone. A 310% rise in norepinephrine. These aren't marginal gains. These are the kinds of numbers that would make a pharmaceutical company very rich, if they could bottle them.
We've seen this territory mapped before — the Finnish longitudinal studies that showed four-to-seven sauna sessions per week cutting cardiovascular mortality by nearly half, the heat shock protein research, the BDNF data. What Patrick does well here is synthesize the athletic performance angle specifically. Most of the longevity research focuses on middle-aged populations. This frames heat acclimation as a tool for people who are already training hard and want to train harder.
The glycogen preservation finding is where I keep landing. A 40-to-50% reduction in glycogen reliance. For endurance athletes, that's enormous. "Hitting the wall" is fundamentally a glycogen depletion event. If heat acclimation means you're burning more fat for fuel and sparing that glycogen reserve, you're not just getting fitter — you're changing your metabolic substrate preference. That's the kind of adaptation that compounds over time.
There's broad consensus on the cardiovascular and endurance adaptations. The plasma volume expansion, the reduced heart rate at equivalent workloads, the improved heat dissipation through earlier sweating — these are well-replicated findings. The muscle hypertrophy pathway via heat shock proteins is also solid, though the human data is thinner than the animal studies Patrick references.
The growth hormone spike is where I'd add nuance. Sixteen-fold sounds extraordinary, and it is — but as we know from other research in this space, your body adapts. By your third sauna session of the week, that spike is down to three or four times baseline. Still meaningful, but the adaptation response weakens with repetition. If you're specifically chasing the growth hormone effect, frequency may actually work against you. Less often, let the signal stay fresh.
For athletes, the prescription here is specific: two 30-minute sessions per week as a minimum. Post-workout sauna appears to amplify the adaptive signal — you've already stressed the system with exercise, and heat extends that stress in a way the body responds to. Evening sessions have the added benefit of dropping your core temperature afterward, improving sleep quality and recovery.
Don't sauna when you're already depleted. Heat is a stressor. It works when you have resources to recover from it. When you're overtrained or fighting illness, the same protocol that builds you up will break you down.
Patrick mentions the runner's high almost in passing, but it deserves more attention. The mechanism she describes — dynorphin creating dysphoria during heat stress, which then upregulates mu-opioid receptor sensitivity, which then makes your natural endorphins hit harder afterward — is exactly the same pathway being studied for depression treatment. A single heat session that elevates core temperature by one to two degrees can produce antidepressant effects lasting up to six weeks. Six weeks from one session.
Athletes talk about sauna as recovery. But what they may be experiencing — that calm, settled feeling after a good session — isn't just the parasympathetic nervous system coming back online. It's their endorphin system running on a more sensitive circuit. They've earned a better high by sitting through discomfort. That's not metaphor. That's biology.