There is an old idea, older than any of the research, that stress followed by rest is the shape of a good life. Heat and cold are two of its most direct expressions.
What heat does.
A sauna session is not a passive experience. The body responds to 20 minutes at 80–100°C the way it responds to a steady cardiovascular effort: heart rate climbs into the 120s, skin vasodilates, core temperature rises a degree or two, and a cascade of heat-shock proteins is produced — the cellular housekeepers that repair damaged protein structures and buffer future stress.
Long-running cohort studies out of Finland — most famously the KIHD study, following 2,315 men for twenty years — have associated frequent sauna use (four to seven sessions a week) with meaningfully lower rates of cardiovascular mortality and all-cause mortality, a correlation that remains after adjustment for the usual confounders. The effect appears dose-responsive: more sessions, more effect.
"Heat, used well, is not a luxury. It is a repeated physiological conversation with the part of the body that decides how old you feel."
What cold does.
Cold water immersion — anything from ten minutes at 15°C to three minutes at 5°C — triggers an entirely different response. A brief, large spike in noradrenaline. A drop in inflammatory markers. A sharp re-engagement of the parasympathetic system in the minutes after exit. It is, reliably, one of the most direct ways to change how you feel in the space of a few minutes.
For athletes, the picture is more nuanced. Cold immediately after resistance training can blunt some of the hypertrophic signalling from that session. For endurance athletes, for inflammation, for perceived recovery, and for subjective wellbeing, the evidence is consistently favourable.
The contrast protocol.
The most robust benefits seem to come not from heat or cold alone, but from the alternation between them. Three rounds of ten minutes in the sauna and two minutes in the ice bath — in either order, repeated — is a good starting structure. Longer-time practitioners often extend the heat and shorten the cold.
What it is not.
Contrast therapy is not a cure. It is not a replacement for sleep, for food, for movement, for people. Most of what we hear from the science community these days — and most of what we see in the clients we install for — suggests it is something humbler and, over a year, more valuable: a compounding practice that slightly improves sleep, slightly improves mood, slightly improves recovery, and slightly improves resilience.
Four times a week, for a year.
Protocols we use.
- Morning, 20 minutes: 10 min sauna · 2 min cold plunge · 8 min sauna. Good for focus and daylight alertness.
- Post-workout, 25 minutes: 15 min sauna · 3 min cold · 7 min sauna. Good for perceived recovery.
- Evening, 30 minutes: Three rounds of 8 min sauna · 1 min cold, finishing on heat. Good for sleep.
Selected reading.
Laukkanen et al., JAMA Internal Medicine, 2015 — sauna use and mortality.
Šrámek et al., Eur J Appl Physiol, 2000 — human physiological responses to immersion in water of varying temperatures.
Buijze et al., PLOS One, 2016 — cold water immersion and workplace absence.
Laukkanen et al., Mayo Clin Proc, 2018 — cardiovascular and other health benefits of sauna bathing.