Why pairing heat with cold multiplies the effect. The contrast-therapy science, Søberg's protocol, the Soeberg principle, and the R1SE Fire & Ice approach.
The mechanism
Sauna vasodilates peripheral blood vessels; cold immersion constricts them. Cycling repeatedly between the two trains vascular tone in a way that resembles aerobic exercise. Endothelial function improves measurably across a 4-week contrast-therapy block (Søberg et al., Cell Reports Medicine 2021).
Brown fat is metabolically active tissue that burns calories to produce heat. Cold immersion (especially repeated cold across weeks) activates and increases brown fat depots in adults; sauna stress potentiates the metabolic effects. Søberg's lab showed brown-fat activity rises measurably with regular winter swimming + sauna combined.
Hormesis is the principle that controlled, time-limited stress strengthens the system. Heat triggers one cascade (HSPs, growth hormone, parasympathetic rebound); cold triggers another (norepinephrine, dopamine, cold-shock proteins). Stacking both within a single session covers both adaptive pathways in the time it takes one to do either alone.
Cold immersion at 3–7°C produces a dopamine rise of roughly 250% above baseline that sustains for 1–3 hours (Šrámek et al., 2000). Pairing it with sauna creates a sequenced neurochemical wave, beta-endorphin from heat, then dopamine from cold, that members consistently describe as the most reliably mood-lifting protocol available without medication.
Contrast therapy puts the cardiovascular system through forced dilation-constriction cycles. Resting heart rate drops, HRV rises, and blood pressure regulation improves over a course of regular sessions. The mortality data on heat alone is strong; cold-paired contrast appears additive though long-cohort data is still emerging.
For sports recovery, the heat-first / cold-later pattern is best supported. Heat immediately after training preserves muscle protein synthesis; cold within 4 hours of resistance training can attenuate mTOR signalling. For aerobic / general recovery, contrast within the same session is fine.
The Søberg protocol
Danish researcher Susanna Søberg's 2021 paper in Cell Reports Medicine produced one of the cleanest dose-response findings in the contrast-therapy literature. Healthy adults who completed approximately 57 minutes of sauna per week (matching the Laukkanen sweet spot) plus at least 11 minutes of cold immersion per week (split into 1–3 minute exposures) showed measurable improvements in brown adipose tissue, glucose tolerance and cardiovascular markers across an 8-week block.
The protocol scales naturally to R1SE's sessions. Three Fire & Ice sessions per week of ~30–45 minutes, with 3–4 cold cycles of 60–90 seconds each, hits both targets comfortably.
Source: Søberg et al., “Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men”, Cell Reports Medicine 2021.
The R1SE Fire & Ice protocol
The Finnish barrel sauna and the ice bath sit metres apart at the Kelham Urban Spa. This is how members typically run a Fire & Ice session, and what we coach in our guided sessions.
10–15 minutes in the Finnish barrel sauna (80–90°C) or the infrared cabin (55–60°C). Get to a deep, full-body sweat. Breathe deeply through the nose.
30–90 seconds in the ice bath at 3–7°C. Sit, fully submerged to the neck, breathing slowly. The first plunge is the hardest, the cold-shock response peaks here.
30–60 seconds standing or sitting outside the cold. Let breathing settle. Avoid rushing back into heat, your skin is constricted, and a too-fast jump in temperature can produce dizziness.
3–5 cycles total. Each subsequent cold is easier; the heat feels more efficient. Total session 35–60 minutes including recovery moments.
End on cold for alertness and a stimulant-like effect that lasts hours. End on heat for parasympathetic settle and easier sleep that night. Choose based on what's next in your day.
Sequencing
Cold immediately after lifting blunts mTOR / muscle protein synthesis. Sauna right after training is fine; save the ice for the next morning or 4+ hours later.
Aerobic adaptations are less affected by post-session cold. Contrast in either direction is fine after a long run, ride or swim.
The contrast protocol does its best work on lighter-load days, restoring vascular tone, settling the nervous system, and delivering the metabolic effects without competing with training adaptations.
End on cold for the sustained dopamine and norepinephrine that prime focus and energy through the morning.
Heat triggers the post-exposure core-temperature drop that supports sleep onset. End the session on heat 90+ minutes before bed.
Book a guided or self-led Fire & Ice session at the Kelham Urban Spa. Sauna, ice and breathwork in one of the only purpose-built contrast-therapy rooms in the North.
Continue Reading
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