What heat and cold actually do.

The heat response

A sauna session at 80–100°C raises core temperature by roughly 1°C over 15–20 minutes. The body responds with peripheral vasodilation, an increase in heart rate comparable to moderate exercise, and the production of heat-shock proteins that assist in cellular repair. Long-term cohort studies — most notably the Finnish KIHD data — associate frequent sauna use with reduced cardiovascular mortality.

The cold response

Brief immersion in water around 4–10°C triggers sympathetic activation, a sharp rise in catecholamines, and a sustained two- to three-fold increase in norepinephrine. This is the mechanism behind the lifted mood and focus that practitioners report for hours afterward. Repeated exposure also drives modest brown adipose tissue activation.

Sleep and recovery

The drop in core temperature that follows a sauna session aligns with the body's pre-sleep cooling curve. Evening sessions — finished one to two hours before bed — are associated with faster sleep onset and reduced nighttime arousal in small trials.

FAQ

Is contrast therapy safe?

For most healthy adults, yes. People with cardiovascular conditions, pregnancy, or uncontrolled blood pressure should consult a clinician first.

How often should I practice?

Two to four sessions per week is the range where most cardiovascular and recovery benefits appear in the literature.

Sauna before or after cold?

Heat first is traditional and follows the body's response curve. Cold first is useful before workouts or for a hard mental reset.