The fitness internet has the attention span of a caffeinated squirrel with a crypto account full of DOGE coin.

A study drops with a huge number and some IG GooRoo between ab shotz and posing in front of his rented fancy car rips that number out of context, sprays it across social media like cheap cologne in a strip mall bathroom, and suddenly every shirtless man with a ring light is telling you the sauna is basically anabolic sorcery.

Then the supplement companies arrive followed fast by the wellness weirdos.

Pure confusion and chaos erupts.

Here is one that does not seem to die:

Sauna and GH, so let’s drag this sauna-growth hormone thing into the harsh LED labl ight before it beats your critical thinking to death with a bamboo whisk.

Leppäluoto and colleagues took 17 poor souls and baked them in a Finnish sauna at 80°C which is 176°F for those of us still measuring things like stubborn Americans, for one hour, twice per day, for seven days.

Growth hormone went up sixteen-fold.

Not 16%.

16 X.

Crazy!

And the internet, being the glorious clown car with square tires that it is, looked at that number and immediately concluded:

“Ah yes. More GH. Therefore: more muscle. More gainZ. More anabolic wizardry. Pass me the cedar bucket, Suffering Sven.”

But that’s not how real physiology works from these LOLs (leapers of logic).

Why? Because acute hormone spikes are sexy on paper and much less exciting in actual tissue.

West et al. (2009) looked at this exact circus from another angle. One group trained arms after squats, which created a much bigger acute systemic hormone spike. The other group trained arms alone, without the giant hormonal fireworks show.

Result?

No extra bump in muscle protein synthesis.
No bonus intracellular signaling jackpot.
No magical “high hormone environment” shortcut to freakier sleeves.

I did a full article for T-Nation back about 12 years ago on this very study, so this is not new news but you still hear that these acute GH spikes are the holy grail.

Remember, just because your blood chemistry throws a little rave does not mean your biceps got the invitation.

And this is where the sauna story gets way more interesting.

Because the useful part is not the GH spike, it is what heat does inside the cell while the internet is outside licking grocery carts and yelling about “natural anabolic optimization.”

Heat stress ramps up heat shock proteins.

Especially HSP72.

These are basically your intracellular pit crew—tiny molecular psychopaths running around inside the cell, helping proteins fold correctly, preventing damaged junk from clumping together, and keeping the machinery from turning into a smoking pile of biologic scrap metal when stress gets high.

This matters.

A lot.

Because adaptation is not built by vibes. It is built by signal handling, and heat appears to improve the way your system handles signal and stress.

In mice, overexpression of HSP72 doubled endurance running capacity and increased mitochondrial content by about 50%. That is not a subtle nudge. That is a metabolic bar fight.

In humans, Ihsan et al. (2020) showed that 60 minutes of whole-body heat stress at roughly 44–50°C enhanced Akt/mTOR-related anabolic signaling, increased heat shock protein mRNA, and pushed up expression tied to mitochondrial biogenesis.

Translation:

Heat may help your body build better machinery while also protecting the machinery you already have.

That is a much cooler story than “GH spike good.”

Then things get even more fun.

Yoon et al. (2017) found that in elderly women, combining low-intensity resistance training with heat stress improved both strength and hypertrophy versus resistance training alone.

That should make your eyebrows punch through your forehead because now we’re not just talking about theoretical cellular nerd nonsense in a lab dungeon.

Now we’re talking about a situation where heat may actually amplify useful training outcomes in a population that often struggles to generate enough training stimulus on its own.

That is real-world interesting even if we don’t know if that study transfers to younger folk.

However, here is the part that should really make you sit up like your glutes just touched a cattle prod:

Unlike cold, heat does not currently show the same interference issue with strength adaptation.

Cold has at least three converging studies showing it can blunt hypertrophy when used right after lifting.

Heat?

Nothing so far suggesting that same post-lifting sabotage effect.

Zero.

Cold gets the social media love because it looks hardcore.

Heat gets ignored because it looks like sitting in a wooden box sweating like a hungover Viking.

But one of those may be helping you adapt without stepping on the throat of your hypertrophy.

The other may be stealing gains while influencers film themselves shivering for engagement.

Cold gets the IG caption while heat gets the adaptation. How about dat nerdy rhyme!

That doesn’t mean sauna = magic gainZ.

It sure as hell does not mean you can replace intelligent training with hot Finnish furniture.

It means the mechanism matters, and if you understand the mechanism, you stop chasing headlines and start using interventions like an adult with a frontal lobe.

Summary

It means stop drooling over acute hormone spikes like they’re anabolic lottery tickets.

Look at what actually changes adaptation.

Yes, look at intracellular signaling, heat shock proteins, mitochondrial biogenesis but make sure to look at the real outcome in hoooomans to see if that intervention helps or interferes with your training.

Inside the Phys Flex Cert, in the heat intervention (1 of 4) I break down the exact sauna variables that matter:

-temperature
-duration
-timing relative to lifting
-how to progress heat exposure
...and how to use heat and cold in blocks instead of randomly mashing them together like a sleep-deprived lab monkey with a bad biohacking habit.

Complete details below:

​https://miket.me/physflex <--full details

Much love, sweat, and intracellular chaperones,
Dr. Mike

PS- The fast-action bonus expires Wednesday, April 23 at midnight PST. That’s tomorrow night. You get a 1-hour private consulting call with me—$250 value—at no extra cost. Sit on that if you want, but that would be a spectacularly dumb way to spend a deadline. You also get the full Q and A pre-recorded session + the Ultimate Red Light full presentation.

PPS “Dr. Mike T. Nelson is one of my go-to guys for applied physiology, which is particularly impressive considering that he always seems to be kiteboarding and must have ears full of blood from his taste in gym music.” — Tommy Wood, MD, PhD

​https://miket.me/physflex <--full details

P3S - Tomorrow I’m kicking open the door on pH and taking a flamethrower to the “lactic acid” myth and why your buffering system may be the difference between real performance and folding like a cheap lawn chair.

References

Leppäluoto, J., Tuominen, M., Väänänen, A., Karpakka, J., & Vuori, J. (1986). Endocrine effects of repeated sauna bathing. Acta Physiologica Scandinavica, 128(3), 467–470.

West, D. W. D., Kujbida, G. W., Moore, D. R., Atherton, P., Burd, N. A., Padzik, J. P., De Lisio, M., Tang, J. E., Parise, G., Rennie, M. J., Baker, S. K., & Phillips, S. M. (2009). Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men. The Journal of Physiology, 587(21), 5239–5247.

Ihsan, M., Deldicque, L., Molphy, J., Britto, F. A., Cherif, A., & Racinais, S. (2020). Skeletal muscle signaling following whole-body and localized heat exposure in humans. Frontiers in Physiology, 11, 839.

Yoon, S. J., Lee, M. J., Lee, H. M., Lee, J. S., & Kim, J. S. (2017). Effect of low-intensity resistance training with heat stress on the HSP72, anabolic hormones, muscle size, and strength in elderly women. Aging Clinical and Experimental Research, 29(5), 977–984.

Henstridge, D. C., Bruce, C. R., Drew, B. G., Tory, K., Kolonics, A., Estevez, E., Chung, J., Watson, N., Gardner, T., Lee-Young, R. S., Connor, T., Watt, M. J., Carpenter, K., Hargreaves, M., McGee, S. L., & Hevener, A. L. (2014). Activating HSP72 in rodent skeletal muscle increases mitochondrial number and oxidative capacity and decreases insulin resistance. Diabetes, 63(6), 1881–1894.

Roberts, L. A., Raastad, T., Markworth, J. F., Figueiredo, V. C., Egner, I. M., Shield, A., Cameron-Smith, D., Coombes, J. S., & Peake, J. M. (2015). Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. The Journal of Physiology, 593(18), 4285–4301.

Fyfe, J. J., Broatch, J. R., Trewin, A. J., Hanson, E. D., Argus, C. K., Garnham, A. P., Halson, S. L., Polman, R. C. J., Bishop, D. J., & Petersen, A. C. (2019). Cold water immersion attenuates anabolic signaling and skeletal muscle fiber hypertrophy, but not strength gain, following whole-body resistance training. Journal of Applied Physiology, 127(5), 1403–1418.

West, D. W. D., Burd, N. A., Staples, A. W., & Phillips, S. M. (2010). Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. Journal of Applied Physiology, 108(1), 60–67.

_____________________

Mike T Nelson CISSN, CSCS, MSME, PhD
Associate Professor, Carrick Institute
Owner, Extreme Human Performance, LLC
Editorial Board Member, STRONG Fitness Mag

Mike T Nelson is a PhD and not a physician or registered dietitian. The contents of this email should not be taken as medical advice. It is not intended to diagnose, treat, cure, or prevent any health problem - nor is it intended to replace the advice of a physician. Always consult your physician or qualified health professional on any matters regarding your health.

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