Cold Boosts Testosterone
Updated: 11 hours ago
Ice bath after exercise increases testosterone by 56% in lean male athletes... one week later.
Summary
For several years I've reported that precooling exercise with an ice bath will boost total testosterone in men, whereas doing an ice bath after exercise will not. A new study shows that's only the case in the short term.
Over a longer time period, such as 10-14 days, it appears that cold-stimulated mitobiogenesis boosts sex hormone synthesis.
The Problem With Ice Bath for Testosterone Research
Wherever I've written about using ice baths to stimulate mitobiogenesis and boost sex hormone synthesis, I've always been careful to confine my claims about men to precooling -- i.e., doing the ice bath before the exercise. Women get an immediate testosterone boost from ice baths, but for men the studies on cold stimulation, exercise, and total testosterone showed that doing the cold after the exercise could suppress testosterone and luteinizing hormone in men.
But there was a problem with those studies. They were only measuring immediate effects. For example, a new study on cold showers measured salivary testosterone in young men 24 hours after four straight days of 10-min cold showers at 17°C (63°F). The subjects were not precooling nor exercising in any way related to the study. Some of the subjects showed increased testsoterone and some showed decreased. The study authors concluded "that cold showers do not trigger a significant hormonal response in adult male athletes, as there were no consistent increases in salivary testosterone under the conditions we tested" (Traylor et al. 2026).
Short-term Effects of Cold Stimulation on Sex Hormone Synthesis: Men vs Women
Because all sex hormone synthesis originates in the mitochondria, we should be able to observe that any therapy that boosts mitochondrial function will also boost testosterone. In theory, more mitochondria means more sex hormone synthesis.
The inner membrane of the mitochondria is where an enzyme called P450scc converts cholesterol into a sex steroid called pregnenolone. All other sex hormones are derived from pregnenolone. (Cortisol also comes from pregnenolone and I will describe the significance of this later).
In women, most of the pregnenolone synthesis happens in skin cells, fat cells, and adrenal glands. The best way to stimulate activity in these three sex hormone sources is cold. That's how women get an immediate testosterone boost from cold stimulation. The ovaries, buried deep inside the woman's abdomen, are unaffected by the cold and they account for only about 25% of total female testosterone, anyway.
One of the biggest sex differences between men and women is that men must make 95% of their testosterone in their testes. That is, men make testosterone in their skin, fat, and adrenal glands, too, but these cells are insufficient to meet a man's higher testosterone needs. In men, the mitochondria in the testes are doing almost all the work.
Rather than stimulating activity in the testes, I think that an ice bath shuts the testes down -- at least in the short term. Remember that the testes are housed in the scrotum, which hang outside a man's body. Although they function better at temperatures that are slightly colder than the core, ice water is too cold for optimal testicular function. My best guess is that exercising after the ice bath helps restore blood circulation to the testes, rewarming them and allowing them to respond to pituitary signaling.
Huge Longer-term Testosterone Gains from Cold Water Immersion Therapy
None of the mechanisms of short-term stimulation speaks to the longer term effects of mitobiogenesis for increased pregnenolone synthesis. It has always made sense to me that the mitochondrial benefits of the ice bath would result in long-term increased in sex hormone production. The problem is that mitobiogenesis can take one or two weeks, and there has never been a cold study of testosterone that ran long enough to observe that effects.
Until now.
Czechian researchers studied 12 young male athletes to investigate this crazy idea that maybe cold water immersion (CWI) might boost mitochondrial function that subsequently results in greater sex hormone synthesis. However, instead of using my precooling protocols, their experimental method involved the traditional approach of ice baths after exercise that we all thought had been discredited. The big difference in this new Czechian study is that the researchers weren't concerned about immediate effects. They allowed 12 days between the pre- and post-experiment measurement of blood serum levels of total testosterone. It's the first study designed to capture the mitobiogenesis effects, rather than just immediate cold stimulation.
The study team recruits young, trained, male athletes. Average age was about 21 years old and average body fat composition was 8.6%. These are exactly the young men that you might think alreayd have healthy levels of testosterone.
But they didn't.
After converting from nmol/l, the baseline (BL) measurements prior to the experimental intervention showed an average of only 350 ng/dl, which many American doctors would consider low enough to treat with testosterone replacement therapy. It's a surprising medical fact that young males today can have good levels of fitness, excellent body composition, and still be working with dysfunctional mitochondria that impair testosterone metabolism.
In other words, these young men were excellent candidates for mitochondrial therapy.
After a 5-day program of intensive exercise program (EC) that including cross-country skiing, weightlifting, running, and cold water immersion in near freezing water (2C) these young men showed no improvement in total testosterone levels compared to baseline (BL) -- which is corroborates every other finding investigating the short-term testosterone effects of ice baths after exercise. However, the researchers did not stop there. They instructed the men to rest for 7 days after the exercise intensive.
No exercise and no cold for one whole week. Testosterone shot up by an average of 56% (ECR, Dytrtová et al. 2026).
This is exactly what we would expect to see when the cold exposure is doing exactly what we know it does -- stimulate mitobiogenesis.
The process of creating new mitochondria takes time -- just like the process of growing new muscle. In How to Increase Brown Fat? I explained that it takes 10-14 days to recruit new brown fat cells. These cells develop thousands of new mitochondria to support non-shivering cold thermogenesis, so it gives us some idea of how long mitobiogenesis takes. Given that the number of days between the BL and ECR measurements was 12, the results in this study correspond well with what we already know about the process of making new mitochondria.
Testosterone vs Cortisol
What's even more interesting about these results is that the researchers also measured increases in cortisol. Most doctors will tell you that cortisol will suppress testsoterone, but that isn't right.
When scientists inject rats with exogenous cortisol, they do see a reduction in total testosterone levels, but it's not because cortisol lowers testosterone per se. The fact is that cortisol is also derived from pregnenolone. In the rat models, injection with exogenous cortisol signals the mitochondria to stop making pregnenolone -- as if the elevated cortisol were causing a backup in sex steriod synthesis further upstream. So exogenous cortisol suppresses pregnenolone, and that limites the amount of pregnenolone available to make testosterone.
Cortisol and testosterone originate in the exact same process, inside the mitochondria, and therefore compete with one another for the limited pregnenolone available. When the body needs more cortisol (e.g., to respond to exercise stress) it routes more pregnenolone into cortisol production, and that makes less available for testosterone.
However, when the number and function of the mitochondria improves, there's more pregnenolone to go around. That is, the results of this cohort suggest the simultaneous boost in both testosterone and cortisol at the same time suggest that at the end of the 12-dat study period, pregnenolone was more abundant. The implication is that mitochondrial function has improved.
What's Wrong with TRT?
The low levels of the testosterone in these young men at the beginning of the study would ordinarily make them good candidates for testosterone replacement therapy (TRT). Men who use TRT to boost their total testosterone levels report better mood, increased competitive drive, better body competition, and greater sex drive.
In other words, my readers on TRT all tell me that it's great.
The problem is that inserting exogenous testosterone into the sex hormone synthesis chain creates the same kind of sex hormone synthesis back up that injecting rats with exogenous cortisol will do. The exogenous testosterone suppresses the synthesis of pregnenolone, and what's worse, it diminishes mitochondrial function in the testes. When TRT goes on too long, the damage to a man's innate capacity for pregnenolone synthesis can become permanent, making them dependent of exogenous T for the rest of their lives.
In my opinion, the men in this study are too young to take chances with TRT. Although it will create an immediate improvement in their quality of life, the rest of permanent dependence on the drug is too great.
Now we know, they needn't worry.
Despite what the short-term studies say, and despite what popular social media influencers think, what this Czechian study tells us is the ice bath is an effective remedy for low total testosterone in young men -- whether they do the ice bath after or before their workout.
References
Jaklová Dytrtová J, Jakl M, Jebavý R, Máčová L, Horníková D, Novák F, Vodička P, Navrátil T, Bičíková M, Elsnicová B, Žurmanová J. Increase in testosterone and cortisol one week after repeated exercise in a cold environment. Frontiers in Physiology. 2026;16:1731242.
Traylor DA, Nunes EA, Lees MJ, Cudaback E, Phillips SM. A Four‐Day Cold Shower Protocol Does Not Increase Salivary Testosterone in a Small Cohort of Male Athletes: A Research Communication. Health Science Reports. 2026 May;9(5):e72432.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.
so its a win win either way, just get in the cold?