Why women experience cold and heat differently | hormones, cycles, and contrast therapy

The contrast therapy space, like much of the health and fitness industry, has historically been researched and discussed with a male physiology as the default. Most of the early cold exposure studies used male subjects. Protocols were developed without accounting for hormonal variability. The result is a body of guidance that is broadly applicable but not always precisely relevant - particularly for women, whose experience of temperature, recovery, and stress response shifts significantly across the menstrual cycle. This is not a reason to avoid cold or heat therapy. It is a reason to understand it more accurately.

Baseline thermoregulation differs

Before accounting for hormonal cycling, there are baseline physiological differences in how women and men regulate temperature. Women tend to have a higher surface-area-to-mass ratio, which affects how quickly heat is lost from the body. Women also typically have lower muscle mass - muscle generates heat during activity - and a different distribution of brown adipose tissue, the metabolically active fat involved in thermogenesis.

These differences mean that women often experience cold immersion as more intense than men do at equivalent temperatures and durations. This is not a psychological difference or a question of tolerance. It is physiological. Recognising it matters for how protocols are approached - and for not comparing your experience of a cold plunge to someone whose body thermoregulates differently.

The follicular phase | more responsive to cold

The menstrual cycle divides broadly into two phases. The follicular phase runs from the first day of menstruation to ovulation - typically days one to fourteen in a standard cycle, though this varies considerably between individuals. During this phase, oestrogen is dominant.

Oestrogen has a mild vasodilatory effect and supports a more stable stress response. Baseline body temperature during the follicular phase is slightly lower. Many women report that cold immersion feels more accessible, the initial shock more manageable, and the recovery afterwards more energising during this phase. If there is an optimal window for building a cold water practice or extending duration, this is generally it.

There is also an argument for timing more demanding sessions - longer cold exposure, higher heat, or the full contrast protocol - to this phase. The hormonal environment is more forgiving. The body's stress response is better buffered. And the mood-lifting effects of both cold and heat tend to feel more pronounced, in part because oestrogen itself has a positive relationship with serotonin and dopamine signalling.

The luteal phase | a different experience

After ovulation, progesterone rises. One of progesterone's effects is a consistent increase in basal body temperature - typically around 0.2 to 0.5 degrees Celsius. This is the temperature shift that forms the basis of fertility tracking, but it has broader implications for how the body responds to thermal stress.

During the luteal phase, cold immersion can feel more intense. The body is already working harder to maintain its elevated temperature, and the contrast with cold water is correspondingly more pronounced. This does not mean avoiding cold therapy during this phase, but it is useful context for sessions that feel harder without obvious external explanation.

Heat therapy tends to feel particularly beneficial during the luteal phase. The warmth is complementary to the body's existing temperature state, and infrared heat's effect on muscle relaxation and cortisol reduction is well suited to the increased physical discomfort and mood variability that many women experience in the days before menstruation.

It is also worth noting that progesterone has a mild anxiolytic effect - it is calming in moderate amounts - but when it drops sharply in the days immediately before menstruation, that withdrawal can contribute to heightened emotional sensitivity and disrupted sleep. A sauna session in this window, precisely because of its effect on cortisol and its ability to induce deep physical relaxation, can be a genuinely useful tool rather than an indulgence.

During menstruation | exploring hormones

The research on cold therapy during menstruation is limited, and individual experience varies considerably. For some women, cold immersion during the first days of their cycle provides meaningful relief from cramping, likely through the anti-inflammatory and analgesic effects of cold exposure. For others, the experience is simply not comfortable, and that response is equally valid.

There are no contraindications to contrast therapy during menstruation for healthy women. The decision is a personal one, and the best guide is attentive observation of your own response rather than a fixed rule in either direction.

Cortisol, the HPA axis, and why stress hits differently

The hypothalamic-pituitary-adrenal axis - the system that governs the stress response - behaves differently in women and men, and those differences interact with contrast therapy in ways that matter. Women tend to show a stronger cortisol response to psychosocial stressors and a different pattern of HPA axis recovery. Oestrogen amplifies certain aspects of the stress response; progesterone moderates it. The result is a stress system that is more variable, more hormonally mediated, and potentially more sensitive to interventions that act on cortisol.

This is relevant because both cold and heat therapy work partly through their effect on the stress response. Cold immersion triggers a sharp, acute cortisol spike followed by a sustained reduction. Regular cold exposure appears to lower baseline cortisol over time. Heat therapy produces a more directly parasympathetic response, reducing cortisol through relaxation rather than the acute challenge-and-recovery mechanism of cold.

For women carrying a high allostatic load - chronic stress, sleep debt, overtraining, or hormonal disruption - the acute cortisol spike of cold immersion is worth approaching with some attention. It is not harmful, but adding an aggressive stress stimulus on top of an already taxed system needs to be balanced. Shorter durations, warmer water temperatures, and prioritising the sauna component during high-stress phases is a reasonable adaptation rather than a compromise.

Perimenopause and menopause | where contrast therapy becomes particularly relevant

The conversation around contrast therapy and women's health becomes especially interesting at perimenopause - the transition period, often beginning in the early to mid-forties, during which oestrogen and progesterone levels become increasingly erratic before declining. This phase is characterised by a loss of hormonal predictability: cycles become irregular, temperature regulation becomes less stable, and many of the symptoms most commonly associated with menopause - hot flushes, night sweats, disrupted sleep, mood shifts, joint discomfort - begin.

Hot flushes are, at their core, a thermoregulatory phenomenon. The hypothalamus, which governs core temperature, becomes hypersensitive to small temperature fluctuations as oestrogen declines. The thermoneutral zone - the temperature range within which the body does not need to actively heat or cool itself - narrows significantly. This is why relatively minor triggers can produce sudden, intense heat responses.

Regular exposure to controlled thermal stress appears to support thermoregulatory function over time. Some women report that consistent sauna use reduces the frequency and intensity of hot flushes, possibly by training the hypothalamus to respond to temperature fluctuation with less alarm. The evidence here is still developing, but the mechanistic logic is coherent, and the anecdotal reports are consistent enough to warrant attention.

Beyond thermoregulation, the cardiovascular benefits of both cold and heat therapy are particularly relevant in the postmenopausal period, when the protective effect of oestrogen on the cardiovascular system is reduced. Heat therapy's effect on cardiovascular efficiency - improved plasma volume, enhanced vasodilation, reduced blood pressure over time - makes it a meaningful complementary practice for women navigating this transition.

Sleep disruption, a near-universal feature of perimenopause, also responds well to regular sauna use. The reduction in cortisol and the deep physical relaxation that follows a heat session can ease the difficulty of falling and staying asleep that many women in this phase experience. This is not a cure, but it is a consistent and low-risk support.

Practical ways to adapt your practice

Understanding the theory is one thing. Translating it into a practice that feels manageable is another. The following is not a rigid protocol - it is a set of observations that many women find useful as starting points.

During the follicular phase, this is generally the time to explore. Try a longer cold immersion. Push the temperature down a degree. Add an extra round to the contrast sequence. Notice how your body responds - you may find significantly more capacity than you expect.

During the luteal phase, lean into the sauna. If cold immersion feels harder, start with heat, take your time warming up, and approach the cold with a shorter target time. The goal in this phase is restoration, not performance. A session that ends with you feeling calm and warm rather than braced and energised is entirely appropriate.

In the days before and during menstruation, follow your body without pressure. If cold immersion offers relief, use it. If it does not appeal, a standalone sauna session is complete in itself and carries its own significant benefits.

Across all phases, the most useful thing you can do is note how sessions feel and what follows them. Energy in the hours after. Sleep quality that night. Mood the following day. Over a few cycles, a pattern emerges - and that pattern is more useful than any generic guidance, because it is yours.

Listening to your body with more precision

The broader point is that consistency in contrast therapy does not require ignoring the variability of female physiology. It requires working with it. Tracking how you feel in each phase - how cold immersion lands, how quickly you warm up, how you feel in the hours after a session - builds a picture that is specific to you.

Some women find they can push duration and intensity in the follicular phase and use the luteal phase for gentler, more restorative sessions. Others find their response relatively consistent across the cycle. Neither is more correct. What matters is that the practice is informed by your actual physiology rather than a generic protocol designed around a different one.

The contrast therapy space is catching up, slowly, to the reality that female physiology is not a variation on a male baseline - it is its own system, with its own logic. Understanding that logic does not make the practice more complicated. It makes it more effective.

Thanks for reading,

The ISKA Team