Is cold plunge too stressful for females?
Summary
Recent appearances by Stacy Sims, PhD on several popular podcasts have cast doubt on the benefits of cold plunge therapy for women. Unfortunately, Sims oversimplified sound bites have allowed viewers to believe that cold plunge might be bad for women, and caused some viewers to discontinue an otherwise healthful practice.
What gets lost in social media are the many benefits women can expect from cold plunge, and a legitimate demarcation of differences between the sexes that can be attributed to underlying physiology, rather than experience.
Women practicing regular ice baths can expect to experience improved thyroid function, better metabolism and increased insulin sensitivity, improved sex health, fewer symptoms of menstruation & menopause, reduced risk of osteoporosis, and better mental health.
Is Cold Plunge Bad for Women?
Several women who watched Stacy Sims, PhD on a popular podcast have written to tell me they got the impression that cold plunging is bad for women. Some of said that, although they enjoyed cold plunging, after they saw Sims on Huberman Lab podcast, or on Diary of a CEO, or on Mel Robbins, they got scared that maybe they were doing something harmful to themselves and they stopped plunging.
What a waste.
Sims is influential because she wrote a best-selling book called Roar that appeals to women (Sims 2016). The principal thesis is that women have been misled by fitness marketing messages that fail to recognize gender differences, and that more careful consideration of unique female physiology will result in better recommendations for female athletes. Paradoxically, Sims makes the case that women are both unique and distinct from men, and also capable of matching or exceeding men on sport and performance measures that are normalized for differences in height and muscle mass. It's a marketing message that resonates with the culture of fempowerment that peaked at the end of the Obama Presidency, and surged again at the conclusion of the Biden Presidency, which coincided with the book's revised edition (Sims & Yeager 2024). Moreover, Sims standing as a Research Associate at New Zealand's SPRINZ-AUT sports science research institute and her published record of scholarship add credibility to her argument that there is "an appalling lack of research done specifically on women in regards to exercise, nutrition, and medicine" (Sims 2025).
To Sims credit, the research on sports performance is dominated by male subjects, and her research on female sports performance helps fill an important knowledge gap with regard to extreme sports and female physiology. Nonetheless, she has never published a study on cold plunge therapy, and her podcast comments are at odds with other accomplished female scientists with superior expertise. For example, Lauren Burns, PhD who won the Olympic gold medal in Taekwondo for Australia at the 2000 Syndey games, has studied female sports performance extensively. Burns has published a series of articles describing the life-style behaviors of elite athletes and, in contradiction to Sims, discovered that the highest achieving female athletes ice bath more often than those who are less accomplished (Burns et al. 2022). Similarly, Josephine Worseck, PhD, the first female Wim Hof-certified instructor in Germany, wrote a book called Die Heilkraft Der Kalte ('The Healing Power of the Cold,' Worseck 2020) in which she describes the health benefits of cold plunge therapy for women.
Gender Differences in Cold Sensitivity
Cold Sensitivity
Sims is correct to acknowledge physiological differences between men and women in relation to cold exposure, but incorrect in her conclusion that women should avoid colder temperatures. When she says that women are more sensitive to cold, she's relying primarily on a 2018 study of Dutch men and women that compared sensitivity to a cold vest. The researchers, pointing out that women typically prefer warmer indoor temperature settings than men, sought to investigate gender differences in cold sensitivity. They discovered that the onset of shivering in women occurs at higher temperatures than in men. This suggests that women, at least those non-menstruating women that were included in the study, are more sensitive to cold than men are--a conclusion that agrees with some earlier findings (e.g., Stevens et al. 1987, Cernych et al. 2017) and disagrees with others. For example, although most studies do indicate that women experience greater cold sensitivity compared to men, a Canadian team found little difference after normalizing the results for differences in body mass and surface area (Tikuisis et al. 2000). When considering a broader sampling of the scientific literature, I can find at least three reasons to avoid Sims' conclusion that women should therefore plunge at warmer temperatures:
The differences that exist between the sexes at the population scale do not say anything about what applies to individuals within those populations. For example, in the figure shown it's obvious that the two data sets have a large area of overlap, indicating that there were several women in the study who were more cold tolerant than several of the men in the study.
The differences in cold sensitivity may be due to prior experience with cold exposure, rather than with inherent biological differences between men and women. That is, Dutch men are more likely to work outdoor jobs in winter, participate in winter sports, and more likely to have prior experience with cold that maintains a stronger thermoregulatory response. For example, a study of Finnish women discovered that just one prior exposure to either wold-body cryotherapy or winter swimming will improve cold tolerance during a second exposure (Smolander et al. 2004).
Cold responses in women can be altered by both stage of menstrual cycle and status of hormonal birth control (Castellani et al. 2016). Although thermogenesis seems to be independent of menstrual phase (Taniguchi et al. 2024), conclusions with regard to hormonal responses that are drawn from any one particular study might be the result of inclusion and sampling biases that fail to provide reliable advice for individual women--particularly those post menopause.
Thermal Defenses
There are principally two mechanisms by which the body defends core temperature in the cold: 1) insulative, and 2) generative. Insulative responses are adaptations that reduce heat losses. Chief among these is vasoconstriction, which reduces blood flow to the extremities, allowing skin temperatures in the limbs, feet, hands, toes, and fingers to drop, while keeping the vital organs in the body core warm. By contrast, generative responses are those that create more heat inside the body to compensate for that which is being lost to the cold. The typical generative response in a body that is not yet cold trained is muscle shivering. The more rare, and probably more effective generative response is non-shivering thermogenesis, which takes place primarily in brown fat (also called brown adipose tissue, BAT). It takes about two weeks of daily cold plunging for a body that is naive to cold training to recruit new brown fat for non-shivering thermogenesis.
A study at the Lithuanian Sports University indicated that the insulative responses are stronger in the female body, and generative responses are stronger in the male body (Solianik et al. 2014), which supports Sims' claim that women "experience vasoconstriction first." However, the study did not explain why the gender difference might be observed. Because both men and women with prior cold training experience were excluded from the study, it may be that both groups lacked brown fat. In that case, the researchers may have measured some inherent biological difference. However, it could also be true that even without a prior deliberate cold exposure practice, the men were better cold acclimated than the women simply because they generally spent more time outdoors during the winter.
Generative metabolic responses to the cold require metabolic energy, which comes from two sources: 1) glucose, or 2) fats. During the first few seconds of a cold plunge, the liver releases glycogen stores to boost blood sugar and fuel cold thermogenesis either through shivering in the muscles, or non-shivering thermogenesis in the brown fat. However, as I wrote in Ice Bath for Type 2 Diabetes, thermogenesis in an ice bath will rapidly clear excess glucose from the bloodstream. In less than a minute, blood glucose reserves may be exhausted, so that the body will resort to burning free fatty acids instead.
A German study comparing male and female cold responses discovered that the strongest free fatty acid response was in men, and women with low body mass index (Höring et al. 2025). In women, high body mass index could be consistent with a more effective insulative response to cold, given that subcutaneous fat provides thermal protection for vital organs in the core. In that case, perhaps more cold is required to create the same generative, fat-burning response.
The study is interesting for interpreting Sims claims, because Sims herself and the female athletes she works with are exceptionally lean. It may be that when she draws upon her experience with extreme female athletes, she notices a strong generative response in them, in the same way that the German study measured. That does not mean that Sims' experiences working with lean, extreme athletes are generalizable to all women. Rather, it suggests that everybody experiences a cold dose-response relationship that is individual to them.
Benefits of Cold Plunge Therapy for Women
There are several dimensions of health and well-being by which women benefit from cold plunge therapy. The core of Sims argument acknowledges that cold plunge is beneficial for women. All she's really saying is that she prefers warmer temperatures for women. The problem is that in her public statements, she fails to summarizes the many reasons that women should consider a regular practice of cold plunging, and instead leaves her viewers with the impression that cold plunging for women is bad. To remedy that misconception, allow me to remind you of the many ways that women benefit from the cold:
Thyroid Function
As I wrote in Cold Cure for Hashimoto's, several documented case studies of women who have resolved thyroid disorders after adopting a cold plunge practice have reached me, and there is some good clinical evidence to suggest that cold modulates thyroid function, even as thyroid function modulates cold response (Sabatino & Vassalle 2025). While women with thyroid disorders typically experience improvements resulting from a regular practice of cold plunge therapy, a study of healthy Finnish women indicated now thyroid abnormalities resulting from a twelve week program of whole-body cryotherapy (Smolander et al. 2009). That is, cold normalizes thyroid function by recruiting brown fat. It thus can correct both hyperthyroid and hypothyroid conditions by restoring the balance between thyroid and brown fat regulation of one another.
Metabolism & Insulin Sensitivity
The metabolic benefits of cold plunge therapy are already well documented. For example, one woman wrote about how she restored her metabolic health in Ketosis and Ice Baths Reversed My Type 2 Diabetes. Her experiences are corroborated by a study of fourteen Polish women who undertook a program of regular winter swimming, and confirmed improvements in insulin sensitivity, and decreases in leptin and insulin levels (Gibas-Dorna et al. 2016).
Sex Health: Testosterone, Fertility, Pregnancy, and PCOS
I documented the sex health and fertility benefits of cold plunge for women in several articles that have been summarized in my recent book Uncommon Testosterone (Seager 2025). For example, most people don't realize that the leading cause of infertility in women of child-bearing age is polycystic ovarian syndrome (PCOS) and that it originates in insulin resistance. Improving insulin sensitivity--e.g., via a program of cold plunge therapy--can reverse PCOS, restore fertility, and normalize testosterone levels (Ye et al. 2021 [in rats]). Additional sex health benefits have been documented in both clinical trials and case studies, including increased sex drive. Moreover, in pregnant women, cold plunge is associated with better birth outcomes
Menstruation, Menopause & Endometriosis
The many women who have reported to me that cold plunge therapy helps them manage menstruation and symptoms of menopause have finally been corroborated and documented by the scientific literature. A survey of over 1000 British women engaged in a program of cold water swimming conducted by the University of Portsmouth discovered that women report improved mood, less irritability, and less pain as a result of their cold swimming program. Moreover, 60% of the respondents said that they believe colder water temperatures result in greater benefits (Pound et al. 2024)--in direct contradiction of Sims claims that warmer temperatures are better for women.
One of the major benefits to cold plunge therapy that Sims does acknowledge in some of her podcast appearances is in the treatment of endometriosis, an painful condition in which the lining of the uterus is found growing outside the uterus (compared with inside, where it belongs). A clinical trial is underway at the University of Adelaide in Australia, and Sims says the early results are promising, albeit unpublished. The motivation for the study is found in the experiences of "many women who have found relief from endometriosis symptoms through cold therapy" and the practitioners who "report improvements in pain management and overall wellbeing" (Davenport 2025).
Bone Metabolism & Osteoporosis
Until now, I've never written about the benefits of cold plunge therapy for bone metabolism. In fact, in Magnesium is Critical for Cold Thermogenesis, I wrote about the risks that long-term cold exposure can present to bone health without sufficient dietary magnesium to fuel mitochondrial activity. Nonetheless, there are two studies that measured improved blood markers of bone metabolism that result from deliberate cold exposure. Both of these are by the same research group in China and they indicate that the metabolic stimulation provided by cold plunge likely extends to bones in a way that may reduce risks of osteoporosis (Mu et al. 2021, Mu et al. 2023).
Mood Disorders
Finally, the mental health benefits of cold plunge therapy--especially at colder temperatures--are exceptional. I've written about this in several articles, including:
For the purposes of this article, I'll mention just two studies. The first is a case of a young woman who suffered from major depression that proved resistant to both drugs and normal talked therapy. A regular program of cold water swimming rescued her. Researchers at the University of Portsmouth documented her remarkable case (Van Tulleken et al. 2018). The second is a clinical trial at Bournemouth University in United Kingdom, where they measured improvements in positive mood (and decreases in negative mood) associated with whole-body cold water immersion. What makes this study so interesting is that they went beyond the usual self-reported measures of subjective well-being that normally constitute the dependent variables in these studies and observed improvements in brain function in areas involved in attention control, emotion, and self-regulation via functional magnetic resonance imaging (fMRI, Yankouskaya et al. 2023).
References
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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.
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