If you’ve ever stepped from a hot tub into a bracing shower - or darted from a sauna into the winter air - you’ve already tried contrast therapy. At its core, it’s simple: alternate heat (sauna, steam room, hot tub, warm bath) with cold (cold shower, plunge, ice bath, wintry lake, even snow). The goal isn’t bravado; it’s about giving your circulation and nervous system a helpful nudge. In Nordic countries, pairing a sauna with an icy dip or snow has long been part of the culture - and the ritual maps neatly onto what we know about physiology.

What’s Going On Under the Skin?

Heat relaxes blood vessels (vasodilation), increases blood flow to skin and muscle, and often eases perceived muscle tightness. Finnish-style sauna typically raises heart rate and cardiac output in a way similar to gentle cardio, which many people experience as deeply relaxing (Mayo Clinic Proceedings review).

Cold tightens vessels (vasoconstriction), counters swelling, and can dampen nerve signalling related to soreness. Short cold-water immersions - commonly 10-15°C in studies - are often used to take the edge off post-exercise muscle soreness (Cochrane Review).

Switching between them creates a circulatory “pumping” effect (expand - constrict - expand), changes skin and muscle perfusion, and gives the autonomic nervous system a workout. Some protocols show acute shifts in heart-rate variability and haemodynamics after sauna - cold sequences (European Journal of Preventive Cardiology).

What the Evidence Actually Says

  • Post-workout soreness and recovery: Systematic reviews suggest that cold-water immersion can reduce delayed-onset muscle soreness versus passive rest in the days after intense exercise, although many trials are small or at risk of bias (Cochrane). A review of contrast water therapy similarly found reduced soreness up to 96 hours, with high heterogeneity and risk of bias (PLOS One). A 2024 network meta-analysis compared hydro and cryotherapy approaches at different temperatures, indicating some short-term advantages for specific protocols (BMC Musculoskeletal Disorders).
  • Sauna on its own: Observational and interventional research links regular Finnish sauna with beneficial cardiovascular markers and post-session reductions in blood pressure for some groups, though the strongest evidence base concerns sauna alone rather than specific hot - cold pairings (Mayo Clinic Proceedings).
  • Mood and alertness: Many people feel calmer after heat and more alert after cold; mechanistic data (catecholamines, autonomic tone) make this plausible. Robust clinical trials isolating mood effects from ritual/context are limited, so treat these as likely short-term effects rather than medical treatments.

Different Ways To Do Hot and Cold

Heat options: Finnish sauna, bio sauna, steam room, hot tub, warm bath or shower.

Cold options: Cold shower, cold plunge or ice bath, natural cold water (with supervision and local safety rules), winter dips, even a brief roll in snow next to the sauna where safe and traditional.

A “Goldilocks” Way To Start (Guidance - Not Gospel)

  1. Pick your heat: Sauna users often feel good in the 70-90°C range for 8-12 minutes in round one. For a hot tub or warm bath, try 37-40°C for 5-10 minutes to start. If you feel light-headed or unwell, stop the heat phase (review).
  2. Move to cold: Cool-to-cold shower for 30-60 seconds, or a plunge at roughly 10-15°C for 30-60 seconds when you’re new to it (Cochrane).
  3. Repeat 2-3 rounds and finish based on your goal: finish cold for alertness or to minimise post-exercise swelling; finish warm for relaxation and sleep.
  4. Frequency: 1-3 sessions per week is plenty for most. If you’re chasing training adaptations, avoid very cold plunges immediately after heavy strength work unless soreness control is more important than gains (a lesson from broader cold-immersion literature).

For Athletes: When It’s Likely To Help

  • After competition or brutal sessions: contrast or cold can help perceived recovery and next-day soreness compared with doing nothing (PLOS One; Cochrane).
  • Back-to-back events: keep cold phases brief and controlled to feel fresher without overdoing it.
  • Strength or hypertrophy focus: if long-term gains are the priority, be cautious with very cold immersion immediately after lifting.

Safety First (Especially Around Cold)

The biggest risks sit on the cold side - particularly sudden immersion. Cold shock can cause an involuntary gasp, rapid breathing, and strain on the heart. Respect the risks and make the cold part gradual and controlled (RNLI guidance; British Heart Foundation).

Who should get medical advice first: anyone with cardiovascular disease or risk factors, uncontrolled hypertension, arrhythmia history, Raynaud’s, neuropathy, cold urticaria, or who is pregnant. If you’re in natural water, follow UK water-safety guidance (RNLI/RLSS), never go alone, and acclimatise gradually. If you fall in by accident, remember Float To Live - float on your back until your breathing settles before attempting to swim (RNLI - Float To Live; RLSS UK).

FAQs

Do I need extreme temperatures?
No. Most people notice short-term relaxation or alertness and reduced soreness with moderate heat and brief cold exposures.

Is sauna - ice “healthier” than hot tub - cold shower?
Not proven. The Finnish ritual is iconic, but head-to-head trials comparing specific pairings are limited. Choose what’s accessible and safe for you.

Can I finish with snow after a sauna?
Yes - in some traditions this is a brief cool-down before re-warming. Keep it short and be mindful of footing.

Sources and Further Reading