Cold water immersion and sauna bathing have re-emerged as prominent interventions in both clinical and performance settings, moving from traditional cultural practices into mainstream wellness and integrative medicine. Sauna bathing has roots in Finnish culture spanning thousands of years, while cold water therapy has been documented in ancient Greek, Roman, and Japanese traditions. In recent decades, modern scientific inquiry has begun to rigorously characterize the physiological mechanisms underlying these therapies, generating a rapidly expanding literature that spans exercise physiology, cardiovascular medicine, and endocrinology. Peptide-based therapies represent a parallel and rapidly evolving domain, encompassing molecules that function as endogenous signaling agents capable of modulating metabolism, inflammation, hormonal balance, and tissue repair at the cellular level [1]. The convergence of these three modalities within a systems-biology framework offers a compelling opportunity to rethink integrative approaches to women’s health.

A critical limitation of the existing evidence base is the historic underrepresentation of women in thermal therapy and exercise physiology research. The majority of foundational studies on cold water immersion and sauna bathing were conducted in male cohorts, predominantly middle-aged Scandinavian men, and caution is therefore warranted when extrapolating findings to women [2]. Women differ from men in several physiologically meaningful ways relevant to these interventions: they exhibit lower basal metabolic rates, higher body fat percentages, different patterns of fat distribution, and distinct thermoregulatory dynamics influenced by estrogen and progesterone fluctuations across the menstrual cycle [3]. Estrogen, for example, augments peripheral vasodilation by directly influencing vascular smooth muscle and endothelial nitric oxide synthase activity, which alters the hemodynamic response to both heat and cold stress compared to male physiology [4]. These differences are not merely quantitative; they represent qualitatively distinct physiological responses that demand female-specific investigation.

The relevance of these interventions is heightened across key female life stages, including the reproductive years, perimenopause, and postmenopause, each characterized by shifting hormonal landscapes that influence cardiometabolic risk, inflammatory tone, musculoskeletal integrity, and psychological well-being. The perimenopausal transition, in particular, is associated with accelerating declines in estrogen that drive increases in central adiposity, insulin resistance, vascular stiffness, and bone resorption which are all domains in which thermal therapies and peptide signaling have mechanistic relevance [2]. This review therefore adopts a life-stage perspective, examining the evidence for CWI, sauna bathing, and peptide interventions with explicit attention to female-specific outcomes, mechanistic pathways, and clinical applicability. Where female-specific data are unavailable, extrapolations from mixed-sex or male cohorts are presented with appropriate caveats, and gaps in the literature are identified as priorities for future research.

For the purposes of this review, a systems-based framework is defined as the evaluation of these interventions according to their convergent effects on shared physiological networks—autonomic, vascular, mitochondrial, and inflammatory—rather than as isolated actions on separate organ systems, and this framework is used throughout to compare the relative strength of evidence and mechanistic contribution of sauna bathing, cold water immersion, and peptide therapy across the female lifespan. Table 1 summarizes this convergence model, outlining the shared physiological pathways through which cold water immersion, sauna bathing, and peptide signaling intersect and the downstream outcomes relevant to women’s health.

Table 1.Mechanism model of thermal stress and peptide signaling in women’s health.

Note: HR indicates heart rate; HSPs, heat shock proteins.

Peptide Signaling (convergent downstream pathway):Hormonal signaling; anti-inflammatory effects; tissue repair/regeneration; metabolic regulation; angiogenesis.

Potential Outcomes in Women’s Health:Cardiovascular health; metabolic health; mood & cognitive function; recovery & performance; hormonal balance & menopausal symptom relief; inflammation modulation.

Cold water immersion (CWI), typically defined as immersion in water at or below 15˚C (59˚F) for a minimum of 30 seconds and up to 15 minutes, induces a cascade of physiological responses beginning with the acute cold shock response [5]. The initial phase, lasting approximately 0 to 90 seconds, is dominated by sympathetic nervous system activation, characterized by rapid vasoconstriction, pronounced increases in heart rate and blood pressure, and a sharp elevation in circulating catecholamines—primarily norepinephrine. This sympathoadrenal surge is accompanied by involuntary gasping, hyperventilation, and increased peripheral resistance, mediated by alpha-adrenergic stimulation of cutaneous vessels. As immersion continues, the body transitions from acute sympathetic dominance toward progressive parasympathetic rebound, with baroreceptor feedback mechanisms moderating the cardiovascular response. With repeated CWI over weeks to months, this autonomic training effect manifests as measurable increases in resting heart rate variability (HRV), a marker of enhanced vagal tone that has been linked to improved stress resilience, anti-inflammatory signaling, and cardiovascular adaptability.

At the cellular level, repeated cold exposure initiates a hormetic adaptation process. Cold-shock proteins, including members of the RNA-binding protein family, are upregulated in response to thermal stress and contribute to enhanced cellular resilience, mitochondrial biogenesis, and anti-aging effects at the molecular level [6]. The transcriptional coactivator PGC-1α, a master regulator of mitochondrial biogenesis and oxidative metabolism, is activated through calcium/calmodulin-dependent kinase (CaMK) pathways stimulated by cold-induced muscle shivering and non-shivering thermogenesis, paralleling the mitochondrial adaptations seen with aerobic exercise training [7]. Brown adipose tissue (BAT) activation during cold immersion contributes to thermogenic energy expenditure and has garnered interest for its potential role in metabolic health, insulin sensitivity, and body composition. Notably, cold-induced thermogenesis in women during the follicular phase of the menstrual cycle has been informally reported to exceed that of men, which has been proposed as an estrogen-mediated enhancement of BAT responsiveness; this is an unpeer-reviewed observation from a secondary source [8] rather than an established finding, and it awaits confirmation in controlled trials with direct BAT measurement.

Clinical evidence supports CWI for reducing delayed onset muscle soreness (DOMS) and improving subjective recovery ratings following exercise in mixed-sex and predominantly male cohorts [9]. The female-specific evidence, however, is more equivocal than this general literature suggests: a 2025 randomized controlled trial enrolling women following exercise-induced muscle damage found that CWI produced no significant improvement in DOMS, muscle strength recovery, or creatine kinase relative to a passive control, and a related 2024 trial similarly found that cold (as opposed to hot) water immersion did not accelerate recovery of force-generating capacity in women [10][11]. This discrepancy between the broader, largely male-derived CWI literature and the limited direct evidence in women underscores that post-exercise CWI benefits should not be assumed to generalize to female physiology without dedicated confirmation. However, timing relative to the type of training remains critical: immediate post-resistance training CWI attenuates mTOR and PGC-1α signaling pathways that drive hypertrophy and mitochondrial adaptation, blunting the anabolic response to strength training [12][13]. For women seeking strength and hypertrophy gains, particularly perimenopausal women for whom lean mass preservation is a clinical priority, this timing consideration warrants particular attention.

Female-specific considerations for CWI extend across the menstrual cycle. During the follicular phase (days 1 - 14), rising estrogen is associated with greater stress resilience and may represent an optimal window for cold exposure, particularly for metabolic and performance purposes; this is an unpeer-reviewed practitioner observation [14] rather than a controlled finding. Evidence suggests that hormonal fluctuations during the menstrual cycle may influence autonomic responses to cold exposure. Some research has hypothesized that the follicular phase may be associated with greater tolerance to cold exposure. However, controlled laboratory studies directly comparing thermosensitivity across menstrual-cycle phases during cold water immersion have generally found no significant differences [15], so menstrual-phase-specific CWI recommendations are provisional pending further research. During the luteal phase (days 15 - 28), elevated progesterone raises basal body temperature and increases sensitivity to stressors, including cold; women report greater perceived difficulty with CWI during this phase, and the cortisol response may be more pronounced, with potential implications for progesterone production—an unpeer-reviewed practitioner observation [13] that has not yet been tested in controlled trials. For perimenopausal and postmenopausal women, cold immersion has been proposed as a strategy for vasomotor symptom management, on the hypothesis that thermoregulatory recalibration from repeated cold exposure could reduce the frequency and severity of hot flashes driven by estrogen withdrawal’s effect on the hypothalamic thermostat. A large self-reported survey of regular cold-water swimmers found that a substantial subset of perimenopausal respondents reported improvement in hot flushes and other symptoms [16], but this observational, non-randomized design cannot establish causation, and no controlled trial has yet tested cold water immersion specifically for vasomotor symptoms; this application should therefore be considered preliminary. Contraindications to CWI include known or suspected cardiovascular disease, arrhythmias, Raynaud’s disease, hypertension, and pregnancy, and immersion should never be undertaken alone or combined with alcohol or other central nervous system depressants.

Sauna bathing produces systemic heat stress through passive whole-body exposure to temperatures typically ranging from 80˚C to 100˚C in traditional Finnish dry saunas, resulting in a core body temperature elevation of 1˚C to 2˚C per session. This thermal load triggers a coordinated physiological response that closely parallels the hemodynamic effects of moderate-to-vigorous aerobic exercise: cardiac output increases by 50% - 70%, heart rate rises to 100 - 150 beats per minute, and peripheral vasodilation redistributes blood flow toward the skin surface to facilitate radiative heat dissipation [17]. Simultaneously, the heat stress activates heat shock proteins (HSPs)—particularly the HSP70 family—which function as molecular chaperones preventing protein aggregation, facilitating refolding of denatured proteins, and maintaining proteostasis that is progressively impaired during aging and cardiovascular disease [18]. Endothelial nitric oxide synthase (eNOS) is upregulated in the high-flow state of sauna bathing, increasing nitric oxide (NO) bioavailability, which plays a fundamental role in vascular tone regulation, prevention of atherosclerosis, and endothelial repair.

The cardiovascular evidence base for sauna bathing is the most robust among the three modalities reviewed. The landmark Finnish Kuopio Ischemic Heart Disease Risk Factor Study, which followed over 2,000 middle-aged participants for up to 20 years, established a striking dose-dependent relationship: individuals using a sauna four to seven times per week demonstrated a 63% reduction in sudden cardiac death, a 61% reduction in stroke risk, and significantly lower rates of hypertension compared to once-weekly users [19]. A 2026 systematic review and meta-analysis synthesizing evidence from large prospective cohort studies and randomized controlled trials confirmed these effects are mediated through upregulation of HSPs, modulation of the autonomic nervous system, and suppression of systemic inflammation, as reflected by reductions in C-reactive protein (CRP) and interleukin-6 (IL-6) [17]. Sauna use has also been associated with improvements in arterial stiffness, resting blood pressure, and lipid profiles across multiple trial designs [17]; it should be noted that a randomized crossover trial of infrared sauna in women did not find significant differences in arterial stiffness or blood pressure relative to exercise or rest, underscoring that these cardiovascular benefits are best supported for traditional Finnish sauna rather than infrared protocols [20].

A growing body of work has examined infrared sauna as an alternative to traditional Finnish sauna, operating at lower temperatures (approximately 45˚C to 60˚C) while producing comparable core temperature elevations through far-infrared wavelengths that penetrate more deeply into tissue. A randomized, controlled crossover trial conducted specifically in premenopausal women compared infrared sauna, aerobic exercise, and a rested control condition across measures of arterial stiffness, heart rate variability, and thermal response [20]. The study found that infrared sauna’s physiological effects were driven primarily by thermoregulatory responses rather than direct exercise-mimetic cardiovascular activation, but still produced meaningful increases in core temperature and sympathovagal modulation. For women over 40, infrared sauna may be particularly accessible given its lower thermal intensity and suitability for those who cannot tolerate traditional high-heat environments, while still activating HSPs and anti-inflammatory pathways relevant to perimenopausal health.

For women in perimenopausal and postmenopausal stages, sauna therapy offers a specific cluster of benefits beyond general cardiovascular health. Vasomotor symptoms—hot flashes and night sweats—arise from estrogen withdrawal’s disruption of the hypothalamic thermostat, rendering women abnormally sensitive to minor temperature fluctuations. Regular sauna use may recalibrate this thermoregulatory threshold through repeated deliberate heat exposure, reducing the frequency and severity of vasomotor episodes, and several small trials have demonstrated improvements in sleep quality and subjective well-being in this population [21]. The accelerated decline in skin collagen that occurs after menopause is also relevant: near-infrared wavelengths similar to those used in infrared saunas have shown capacity to stimulate fibroblast activity and collagen synthesis in photobiomodulation studies, potentially complementing the effects of collagen peptide supplementation [22]. Safety considerations for sauna use include adequate pre-session hydration, avoidance during febrile illness or active infection, and medical consultation for individuals with hypertension, cardiac arrhythmias, or conditions requiring strict thermal regulation. Table 2 summarizes the evidence hierarchy across all three modalities, ranking interventions by study design quality from randomized controlled trials down to preclinical and case-report-level evidence.

Table 2. Evidence hierarchy of thermal and peptide interventions in women’s health.

Note: Evidence quality generally decreases moving down the table (strong evidence reflects stronger clinical confidence; emerging/preclinical evidence carries greater uncertainty). RCT indicates randomized controlled trial; BP, blood pressure.

Peptide therapy can be categorized into three evidence tiers. Tier 1 includes FDA-approved peptide therapeutics. Tier 2 includes predominantly off-label agents, for which human evidence exists but remains limited. Tier 3 includes investigational compounds such as BPC-157, MOTS-c, and humanin, whose proposed applications are supported primarily by preclinical studies and early-stage human research.

Peptides are short chains of amino acids that function as signaling molecules regulating metabolism, inflammation, and tissue repair [23]. Structurally, peptides occupy a strategic position between small molecules and biologics, offering high target specificity, favorable safety profiles, and a capacity to mimic endogenous ligands—particularly at G protein-coupled receptors (GPCRs) that regulate numerous physiological processes. Peptide-based therapeutics have grown from a niche research tool into a mainstream drug class, with dozens of FDA approvals achieved over the past decade and hundreds more candidates in clinical and preclinical development [24]. Despite this progress, the evidence base for many peptides in women’s health remains heterogeneous, spanning rigorously validated pharmacologic agents to experimental compounds evaluated predominantly in animal models.

Thermal therapies and peptide signaling converge on a set of shared physiological pathways that constitute a unifying mechanistic framework for their collective relevance to women’s health. Chief among these convergent pathways are autonomic nervous system modulation, mitochondrial adaptation, vascular remodeling, and cellular stress signaling. Cold water immersion and sauna bathing, despite producing opposing thermal stimuli, both activate robust neuroendocrine responses that recalibrate autonomic balance: CWI through an initial sympathetic surge followed by parasympathetic rebound and increased HRV, and sauna bathing through heat-induced vasodilation and biphasic autonomic modulation involving both sympathetic activation during heat exposure and parasympathetic recovery afterward [17]. This shared autonomic recalibration is clinically significant in women, given that reduced HRV and impaired autonomic regulation are independent predictors of cardiovascular risk that worsen with the hormonal shifts of menopause. Peptide therapies intersect this framework through their roles in vascular regulation, metabolic signaling, and cellular repair—GLP-1 receptor agonists, for instance, exert direct cardioprotective and autonomic-modulating effects beyond their glycemic actions [26].

A critical pattern emerges when the evidence base is examined rather than simply re-tabulated (see Table 2 and the preceding sections for tier-by-tier detail): the interventions with the strongest mechanistic rationale for female-specific application—menstrual-phase-dependent CWI responses, thermally mediated vasomotor symptom relief—are precisely those with the thinnest direct evidentiary support, while the modalities with the deepest overall evidence base, such as sauna cardiovascular outcomes and GLP-1 metabolic effects, were established largely in cohorts and endpoints not designed to test female-specific mechanisms. This inversion, rather than a simple ranking of which modality is \“most effective,\” is the central epistemic problem this review surfaces. It implies that clinical guidance should weight not only the overall evidence tier of a therapy, but whether the specific claim being extended to a female patient has itself been tested in women.

A critical limitation of this review, and of the broader field, is the persistent gap in female-specific data. The majority of seminal studies on thermal therapies were conducted in male-dominant or male-only cohorts, and even when women were included, analyses were rarely stratified by menstrual phase, menopausal status, or hormonal context—variables that materially alter physiological responses to thermal stress [3]. Similarly, peptide therapy research has been conducted predominantly in male animal models and male human participants, leaving the female hormonal and metabolic context largely unexplored. This is particularly consequential given the growing recognition that women are not simply smaller men physiologically: sex hormones modulate receptor expression, autonomic tone, thermoregulatory thresholds, adipose tissue biology, and inflammatory signaling in ways that can fundamentally alter both the magnitude and the nature of responses to these interventions.

From a clinical integration standpoint, these three modalities are not mutually exclusive and may produce additive or synergistic benefits when combined thoughtfully. The Nordic practice of alternating sauna and cold water immersion—often referred to as contrast therapy—is proposed to leverage the opposing vascular responses of heat-induced vasodilation and cold-induced vasoconstriction to produce a pumping effect on peripheral circulation and, potentially, a more pronounced autonomic training signal than either modality alone; as noted above, this remains a theoretical extrapolation pending controlled comparative trials, particularly in women. Peptide therapies, particularly collagen peptides and GLP-1 receptor agonists, may complement thermal modalities by supporting the musculoskeletal and metabolic substrates upon which the benefits of thermal stress depend. Emerging clinical frameworks in regenerative and integrative medicine are beginning to formalize these combinations into protocol-based approaches tailored to individual hormonal profiles, fitness levels, and health goals—a personalized medicine paradigm that aligns well with the heterogeneous physiological landscape of women’s health across the lifespan.

Cold water immersion, sauna bathing, and peptide-based interventions converge on a shared set of physiological pathways—autonomic modulation, vascular remodeling, and mitochondrial adaptation—that position them as a coherent, systems-based framework for women’s health rather than three unrelated modalities. Sauna bathing offers the deepest cardiovascular evidence base of the three; cold water immersion and peptide therapies span a wider range from well-validated (GLP-1 agonists, collagen peptides) to investigational (BPC-157, mitochondrial peptides), with the comparative strength of evidence for each detailed in Table 2 and the corresponding sections above.

The central limitation across this field is the persistent underrepresentation of women—and especially women stratified by hormonal context—in clinical research. Addressing this gap is not merely a matter of equity; it is a scientific necessity, given that female physiology meaningfully alters thermoregulatory, autonomic, and metabolic responses to these interventions. Future research priorities should include randomized controlled trials of CWI and sauna bathing in female-only cohorts stratified by menstrual phase and menopausal status; mechanistic studies examining how estrogen and progesterone modulate responses to thermal stress; dose-finding trials for emerging peptide therapies in female populations with relevant comorbidities; and investigations of combined thermal-peptide protocols that leverage their convergent pathways. Standardization of intervention protocols—temperature, duration, frequency, and timing relative to the menstrual cycle—is essential to enable cross-study comparison and the development of evidence-based clinical guidelines. As the evidence base matures, these modalities hold substantial promise for a personalized, integrative approach to women’s health that honors the complexity of female physiology rather than treating it as a variation from a male default.

The authors thank the Bard Cancer Institute and Angio Institute for their collaborative support of this work.

Conceptualization, N.C.; methodology, N.C. and L.N.; investigation, N.C., L.N., L.G., and R.B.; writing—original draft preparation, N.C.; writing—review and editing, N.C., L.N., L.G., and R.B.; supervision, R.B. All authors have read and agreed to the published version of the manuscript.