Cold plunge had its moment. The gasping-in-an-ice-bath videos. The dopamine-spike headlines. The biohacker influencers standing in freezing water in their back gardens, claiming it fixed everything.
The science was real, cold exposure does increase norepinephrine, does reduce inflammation, does improve mood. But cold alone was always half the intervention. The older, deeper body of research consistently shows that the combination of heat and cold produces effects that neither modality achieves independently.
That combination is contrast therapy. And the data suggests it may be the most underutilised recovery protocol available to athletes and non-athletes alike.
The short answer: Contrast therapy alternates between heat exposure (sauna, 80–100°C) and cold exposure (cold plunge and sauna guide, 3–15°C) in a deliberate ratio. The research-backed protocol is a 3:1 to 5:1 heat-to-cold ratio, typically 15–20 minutes of sauna followed by 3–5 minutes of cold, repeated for 2–4 rounds, ending on cold. This triggers cardiovascular conditioning, accelerates recovery, boosts norepinephrine by 200–300%, and produces a sustained mood and energy lift that cold plunge alone cannot match.
Last reviewed: April 2026
What Contrast Therapy Actually Does
Contrast therapy creates a rapid oscillation between vasodilation (heat) and vasoconstriction (cold). In a sauna at 85°C, peripheral blood vessels dilate, up to three-quarters of total blood flow redirects to the skin surface. Heart rate elevates to 100–150 BPM. Cardiac output increases by 60–70%.
Then you enter cold water at 5–10°C. The blood vessels constrict violently. Blood redirects to the core. Heart rate drops. The nervous system shifts from sympathetic to a parasympathetic recovery response, amplified by the preceding thermal stress.
This oscillation acts as a vascular pump. It drives blood flow through tissues more aggressively than either heat or cold alone.
The Five Mechanisms
The Protocol: Ratios, Temperatures, and Timing
Sample Sessions
The Søberg Principle: End on Cold
Dr. Susanna Søberg's research emphasises ending on cold, allowing the body to rewarm naturally rather than stepping back into heat. This natural rewarming activates brown adipose tissue and extends the metabolic and mood benefits.
Søberg's minimum weekly dose: 57 minutes of heat + 11 minutes of cold per week, spread across at least 3 sessions.
Contrast Therapy vs Cold Plunge Alone
The question is not whether cold exposure works, it does. The question is whether you are leaving benefits on the table by skipping the heat.
Cold plunge alone delivers norepinephrine and brown fat activation, but limited cardiovascular conditioning, zero heat shock proteins, and mood elevation lasting only 30–60 minutes. Contrast therapy delivers all of the above plus the vascular pump effect, HSP activation, compounded endorphin response, and mood elevation lasting 3–5 hours.
Cold plunge was never the whole story. The contrast is where the adaptation lives.
Making the Heat Rounds Count
The limiting factor in contrast therapy is almost always the sauna rounds, not the cold. The challenge is heat stratification, inside the sauna, the air at your head level can be 10–15°C hotter than at bench level. The hypothalamus reads this elevated scalp temperature and fires the exit signal before your core temperature has reached the target.
A merino wool sauna hat buffers the scalp from the hottest air, delaying the premature exit signal and allowing you to complete the full sauna rounds that make contrast therapy effective.
Take the Rí Sauna Quiz to find the contrast therapy protocol that matches your goals and experience level. Free.
Related from Rí Science
- Cold Plunge and Sauna: The Complete Guide
- Sauna Before or After Workout?
- The Huberman Sauna Protocol
- Does Sauna Help Muscle Recovery?
- Sauna Safety: How to Know When to Leave
Frequently Asked Questions
What is the Søberg protocol for contrast therapy?
Dr. Susanna Søberg recommends ending on cold rather than heat to maximise metabolic benefits. The core framework involves alternating sauna (three rounds of 10–15 minutes at 80+ °C) and cold water (1–3 minutes at 2–10 °C), finishing with cold for sustained norepinephrine release and brown fat activation.
How long should you stay in cold water during contrast therapy?
One to three minutes at 5–15 °C per round is effective. Even 30–60 seconds triggers significant norepinephrine release. Start shorter and adapt gradually. Consistency across sessions matters more than extreme duration in any single cold exposure.
Does contrast therapy speed up recovery?
Evidence supports modest recovery benefits. Alternating vasodilation from heat and vasoconstriction from cold creates a vascular pumping effect that may enhance circulation and reduce inflammation. Multiple studies show reduced delayed-onset muscle soreness. However, cold immersion immediately after strength training may blunt some anabolic signalling.
Should you end contrast therapy on hot or cold?
Ending cold maximises norepinephrine, dopamine elevation, and metabolic stimulation. Ending hot promotes muscle relaxation and better sleep quality. For athletic recovery, ending cold is generally preferred. For evening relaxation and sleep, ending warm may be more beneficial.
How many rounds of hot and cold should you do?
Three to four rounds is most commonly studied. A typical session involves three rounds of 10–15 minutes sauna followed by 1–3 minutes cold water. Total session time ranges from 40 to 60 minutes. Beginners should start with two rounds and increase gradually.
What are the norepinephrine benefits of contrast therapy?
Cold water immersion triggers norepinephrine increases of 200–300% above baseline. This neurotransmitter enhances alertness, focus, and mood while reducing inflammation. When combined with prior heat exposure, the thermal contrast amplifies the response, producing more sustained elevation than cold exposure alone.
Sources
- Søberg S, Löfgren J, Philipsen FE, et al. "Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men." Cell Reports Medicine, 2021.
- Cochrane DJ. "Alternating hot and cold water immersion for athlete recovery: a review." Physical Therapy in Sport, 2004.
The information in this article is for educational purposes only and is not medical advice. Consult your doctor before beginning any sauna or cold exposure protocol.
Last updated: 31 March 2026