Key Takeaways

  • The minimum effective weekly cold exposure is 11 minutes total, divided across 2 to 3 sessions.
  • The minimum effective sauna exposure is 57 minutes total per week at roughly 80°C.
  • Ending contrast therapy on cold forces the body to actively generate heat, activating brown fat and neurotransmitters for hours afterward.
  • Water temperature does not need to be freezing to produce metabolic adaptation; 15°C works as well as 2°C.
  • You can apply these findings through the Søberg Contrast Therapy Protocol.

The Søberg Contrast Therapy Protocol

Weekly Volume Targets: Aim for 11 minutes total of cold water immersion and 57 minutes total of sauna exposure per week.

Session Frequency and Distribution: Distribute the weekly volume across 2 to 3 days per week, dividing each exposure day into 2 to 3 cold dips and 2 sauna rounds.

Per-Round Durations and Temperatures: Cold water immersions should last 1 to 2 minutes each (water around 15°C down to 2-4°C). Sauna sessions should last 10 to 15 minutes each at approximately 80°C.

The Søberg Principle (Ending Rule): Always start in the cold and end on the cold. Never end with sauna or external heating; forcing the body to rewarm itself keeps brown adipose tissue and shivering pathways activated for hours post-exposure.

Dr. Susanna Søberg discovered these exact parameters while tracking cold-water swimmers and sauna users in Denmark. As Huberman explained, “Could we talk about what I refer to as the Soberg principle which is to end on cold in order to force your body to heat itself back up and thereby increase metabolism further still.” (play from 33:00)

Søberg confirmed the core mechanism: “So when you end on the cold, you force your body to heat up by itself and that will require that you keep your brown fat activated and also your muscles which is a good thing.” (play from 33:14) Most people ruin the metabolic benefit of contrast therapy by stepping into a hot shower or returning to the sauna right before heading home. Doing that blunts endogenous thermogenesis. “If you end on the cold you have an exercise for your body going on for hours afterwards and that's not only on your metabolism but it's also going to keep your neurotransmitters activated as well,” (play from 33:46) Søberg noted.

Her data also demystified the time requirements. As Søberg described her study, “When we then calculated the numbers together, we can see that this ended up being 11 minutes in total per week, so not in one session of course but they had two to three visits to the water and the sauna per week.” (play from 26:45) For heat, “my study showed 57 minutes in total per week. And if we also then divide it out on these two to three days and two sessions each day correspond to 10 to 15 minutes.” (play from 28:04)

When This Works (and When It Doesn't)

This framework works when your goal is baseline metabolic health, brown adipose tissue recruitment, and better glucose regulation without turning biohacking into a full-time job. It is designed around the minimum effective dose, giving you the physiological benefits of cold shock without the systemic fatigue that comes from staying in freezing water until your hands stop working.

It breaks down if you treat it as an endurance test. Overstaying in near-freezing water or sitting in an 80°C sauna until you feel lightheaded creates excessive cardiovascular strain and cellular exhaustion rather than healthy adaptation. It also fails if you use deliberate cold immediately after heavy strength training, because the cold blunts the natural inflammatory cascade required for muscle hypertrophy.

What to Do With This

If you have access to a local bathhouse, gym, or cold plunge this week, schedule two 30-minute blocks on Tuesday and Friday mornings.

Do not jump in blindly. Start your Tuesday session with a 2-minute dip in 12°C to 15°C water. Step out, dry off lightly, and sit in the sauna at 80°C for 12 minutes. Repeat that cycle twice, and finish with a final 2-minute cold immersion. When you step out of the cold tub the last time, dry off with a towel, put on your clothes, and refuse the urge to sit under a hot shower or wrap yourself in heated blankets. Let your body shiver and rewarm itself over the next hour while you sit down at your desk to work.