Contrast therapy eases soreness a little, and its bigger effect is on your heart

Key takeaways

• A 2013 review of 18 small trials found that alternating hot and cold water eased soreness after hard exercise more than resting did, but every trial carried a high risk of bias.
• In the same review, contrast water worked about as well as plain cold water, stretching or compression, so the switching itself hasn’t proven to add much.
• In a 2020 study of 55 young men, heart rates near 126 beats a minute at the end of a hot sauna dropped to about 66 right after two minutes in cold water.
• Finnish heart researchers list unstable angina, a recent heart attack, uncontrolled high blood pressure, decompensated heart failure and severe aortic stenosis as reasons to skip the sauna.
• Stay sober, ease into cold water instead of diving head-first, keep rounds short, and stop at the first chest pain, pounding heart or dizziness.

In the winter of 1849, a young Bavarian studying for the priesthood, sick with tuberculosis, began taking brief dips in the Danube River two or three times a week¹. His name was Sebastian Kneipp.

Kneipp kept experimenting on himself. He went on to become a priest in the village of Wörishofen, where he treated poor families with water, plain food and orderly daily habits¹. Patients came from across Europe, some of them royalty, and Kneipp Societies sprang up in Germany and the United States¹.

Then Kneipp did something wellness sellers rarely do. He warned people against overusing cold water and said he had softened his own treatment three times¹.

That lesson fits today’s version of water therapy. Contrast therapy means switching between heat and cold: a sauna followed by a cold plunge, a hot tub followed by an ice tub, or a shower that ends with a blast of cold.

Athletes use it for sore legs. Spas sell it as a reset. The research shows a modest benefit for soreness, no clear advantage over simpler methods, and big, fast swings in heart rate and blood pressure. Those swings are the part to plan around.

A priest and Nordic bathers made hot and cold a habit

Kneipp’s cure leaned mostly on cold water. He also prescribed early bedtimes, plain meals with little meat, and barefoot walks in dewy grass¹. His book, Meine Wasserkur (“My Water Cure”), first appeared in 1886 and reached English readers by 1891¹.

In Finland, the hot-cold rhythm grew out of daily life. Almost every Finnish family has a sauna². Bathers typically sit in the heat for 5 to 30 minutes, step out to cool off, then go back in, repeating the cycle as many times as they can tolerate².

Cooling off doesn’t have to mean ice. Finnish researchers describe the usual practice as short sauna stays alternating with a swim, a shower or simply resting at room temperature⁶.

Across Scandinavia, winter swimmers pair brief dips in cold water with hot sauna sessions³. In a small University of Copenhagen study, men who had done this weekly for at least two years showed a smaller jump in pulse and blood pressure when a hand went into cold water³. That hints that the body adapts. With only eight swimmers, all men, the researchers couldn’t say the habit caused the difference³.

Long tradition shows that people find hot-cold bathing worth doing. Only trials can show what the switching does for recovery or health.

For sore muscles, switching helps a little, about as much as cold alone

The first systematic review of contrast water for athletic recovery appeared in 2013 in the journal PLoS ONE, written by François Bieuzen, Chris Bleakley and Joseph Costello, researchers in France, Northern Ireland and Australia⁴. It pooled 18 randomized trials, studies that assign people to treatments by chance, with 356 participants⁴.

To count, a study had to use contrast water within an hour after hard exercise meant to strain and damage muscle. Cold water had to be 15°C (59°F) or colder, and hot water above 35°C (95°F)⁴.

The typical routine looked like this⁴:

• Cold: about 1 minute, at 8°C to 15°C (46°F to 59°F), averaging about 11°C (52°F).
• Hot: 1 to 3 minutes, at 35.5°C to 45°C (96°F to 113°F), averaging about 39°C (102°F).
• Total: 6 to 24 minutes per session, repeated for one to four sessions.

Compared with doing nothing, contrast water cut soreness at every time point measured and reduced the loss of strength after exercise⁴. A blood marker of muscle damage called creatine kinase was lower only at 48 hours⁴.

Compared with other options, the advantage mostly vanished. In 10 trials against plain cold water, soreness didn’t differ⁴. Against active recovery, compression garments or stretching, the review found little or no difference⁴. Two trials tested 6, 12 and 18 minutes of contrast, and longer sessions didn’t ease soreness more⁴.

The size of the effect matters, too. Most soreness reductions were small, under 9% on a standard 10-centimeter pain scale⁴. The authors noted that people usually need a change of 14% to 25% before they notice relief⁴.

Every trial had a high risk of bias. No trial blinded its participants, so everyone knew which treatment they got, and the trials rarely looked for side effects⁴.

A larger 2024 analysis in BMC Musculoskeletal Disorders pooled 57 studies with 1,220 healthy people⁵. Contrast water ranked first for bringing down creatine kinase. Other cold treatments, grouped as cryotherapy, ranked first for soreness and jumping ability, and the authors recommended cold water immersion and cryotherapy for practice⁵.

What about the popular idea that switching temperatures “pumps” waste out of muscles, as vessels narrow in cold and widen in heat? The 2013 reviewers called that a common explanation that hasn’t been proven⁴.

If you lift weights to build strength, read our cold plunge article for a separate catch involving cold baths after training. We found no long-term trial of contrast therapy and muscle growth.

What hot-then-cold does to your heart and blood pressure

Heat and cold push your circulation in opposite directions, fast.

In a hot sauna, blood rushes to your skin to shed heat. Heart rate can climb to 120 to 150 beats a minute, and blood pressure tends to fall⁶. Levels of norepinephrine, a stress hormone, rise⁶.

Cold does nearly the reverse. When cold water hits your skin, the blood vessels there clamp down, and heart rate and blood pressure spike right away⁷. More blood is pushed toward the center of your body, so the heart has to work harder⁶.

A 2020 study measured that switch in 55 sedentary male college students⁸. After 16 minutes in a sauna at about 90°C (194°F), their heart rates averaged about 126 to 128 beats a minute⁸.

Then one group sat neck-deep in 10°C to 12°C (50°F to 54°F) water for two minutes. Right afterward, their average heart rate was about 66, while a group that took a brief cold shower and rested averaged about 85⁸. Some heart rates in the immersion group dipped below 60⁸.

That’s a drop of about 60 beats in a few minutes. These were healthy young men, measured with consumer heart-rate monitors after a single session⁸. The study can’t tell us how a weaker heart would respond.

A team of Finnish sauna researchers led by Jari Laukkanen reviewed the evidence in 2018 in Mayo Clinic Proceedings⁶. For people with heart disease, they wrote, a cold shock after the heat can set off abnormal rhythms in both the upper and lower chambers of the heart, so they generally advise against it⁶. They also described fatal cases in which people plunged head-first into cold water straight from the heat, and they blamed a sudden squeeze on the heart’s own arteries⁶.

The same review mentions one study in which people with heart failure, and without serious rhythm problems, tolerated sauna and cold water. The authors said larger, well-designed studies are needed⁶.

One thing to keep in mind about these sources: Laukkanen is also a co-author of the 2020 cold-water study above⁸. So the review and that study come partly from the same research group and aren’t independent checks on each other.

An evidence map for contrast therapy claims

This table uses four levels: strong evidence, promising but early, not enough evidence, and evidence says no (or unsafe).

Claim	Evidence level	What the research shows
Less soreness after hard exercise, compared with resting	Promising but early	18 small trials favored contrast water; effects were small and every trial had a high risk of bias4
Less strength loss in the days after hard exercise	Promising but early	Same review found less strength loss than resting, in small, unblinded trials4
Lower levels of a muscle-damage blood marker	Promising but early	Ranked first in a 2024 network analysis; clearly lower only at 48 hours in the 2013 review45
Works better than a cold plunge, stretching or compression	Evidence says no	Head-to-head trials found little or no difference4
Longer sessions work better	Evidence says no	Two small trials found 18 minutes no better than 6 for soreness4
Switching temperatures “pumps” waste from muscles	Not enough evidence	A popular explanation that hasn’t been tested well4
Fewer sick days from hot-to-cold showers	Promising but early	One large, unblinded trial found 29% less sick leave but no fewer days of illness10
Safe for people with unstable heart disease	Evidence says no, or unsafe	Cold after heat can provoke abnormal rhythms in heart patients; experts list unstable angina and recent heart attack among reasons to skip6

Who should skip it, and who should ask first

The 2018 Finnish review lists these as reasons not to use a sauna at all⁶. It’s one team’s list, not a formal guideline, so treat it as a floor rather than a full medical screen:

• Unstable angina, meaning chest pain that is new, worsening or happens at rest
• A recent heart attack
• Uncontrolled high blood pressure
• Heart failure that is getting worse or isn’t controlled
• Severe aortic stenosis, a tightly narrowed heart valve

They advise caution for severe valve disease and for orthostatic hypotension, a drop in blood pressure when you stand that can make you dizzy or faint⁶. Fever and acute illness are also reasons to wait⁶.

Adding cold raises the stakes. Cold shock is most dangerous for people whose hearts or blood vessels are already vulnerable, and it raises the risk of heart failure and stroke in those people⁷. If you have heart disease of any kind, get your cardiologist’s advice before you add a plunge.

Alcohol and hot-cold bathing don’t mix. Between 1970 and 1986, 230 people in Finland died of overheating, most of them in saunas and most after drinking². Alcohol can drop blood pressure enough to make you faint². In one Finnish hospital review, about 40% of sauna-related burns happened to people under the influence⁶.

Pregnancy calls for a conversation with your prenatal provider. A 2019 review of 12 studies with 347 pregnant women found that up to 20 minutes in a 70°C (158°F) dry sauna, or in a 40°C (104°F) bath, kept core temperature below 39°C (102.2°F), the level linked to birth defects⁹. The evidence was limited and uneven in quality, and the team said its advice could shift as new studies come in¹¹. The studies didn’t test cold plunges or hotter saunas, so contrast routines in pregnancy remain untested.

Cold-sensitive fingers and toes. In a large Dutch trial of showers that ended with cold water, a lingering cold feeling was the most common side effect, including in three people with Raynaud’s phenomenon¹⁰. If cold turns your fingers white or blue, keep the cold step mild or skip it.

A safer contrast routine, step by step

This routine combines what the trials used with what safety research shows about heat and cold. It’s a starting point for healthy adults, not a prescription.

Before you start, run this ready check. Skip today if any answer is yes:

• Have I had alcohol in the last few hours?
• Do I feel sick, feverish, dizzy or already dehydrated?
• Have I had chest pain, a racing or skipping heart, or fainting lately that no doctor has checked?
• Am I alone, with nobody nearby if something goes wrong?

Step	Tub or bath version	Sauna version	Shower version
Warm phase	1 to 3 minutes in hot water, about 38°C to 40°C (100°F to 104°F)4	Start with a short stay, near the low end of the 5 to 30 minutes Finns use2	Shower as warm as you like
Cool phase	About 1 minute in water near 10°C to 15°C (50°F to 59°F)4	Cool shower, room-temperature rest, or a cold plunge if you’re healthy and used to cold6	End with 30 to 90 seconds of cold water10
Rounds	A few rounds, 6 to 24 minutes total; more time didn’t help in trials4	Repeat only as long as you feel well2	One cold finish is enough; 30 seconds did as well as 9010
Finish	Sit, dry off, rewarm gently	Rest and drink water before you drive	Dry off and dress warmly

A few rules apply to every version:

1. Enter cold water slowly. Never dive or jump in head-first after heat⁶.
2. Keep your head above water and keep breathing. Holding your breath under cold water can trigger abnormal heart rhythms⁷.
3. Stand up slowly. Heat lowers blood pressure, and some people get dizzy when they rise⁶.
4. Build up over weeks. Start cautiously and lengthen sessions only as you learn your tolerance⁶.

Leave right away if you feel chest pain or pressure, a pounding or skipping heartbeat, dizziness, confusion, or breathing that won’t settle.

When to get help. Call 911 if someone faints, has chest pain or becomes confused during or after a session. Report a sauna, tub or chiller that burns, shocks or injures someone to the Consumer Product Safety Commission at SaferProducts.gov, and report misleading health claims to the FTC at ReportFraud.ftc.gov.

Heat and cold as a tonic, with the founder’s caution

Natural health has long treated water as medicine you can feel. Kneipp built a movement on that idea, and Finnish families made the hot-cold cycle part of ordinary life¹².

The research supports a modest version of that tradition. Your body seems to adapt to repeated cold, as the Scandinavian swimmers’ calmer responses hint³. And contrast water seems to take a little of the edge off soreness after hard work⁴.

What tradition also teaches, through Kneipp himself, is restraint¹. You can follow his lead. Start gentle, notice how your body reacts, and treat the cold step as a strong dose rather than a test of grit.

If a session leaves you feeling calm and refreshed, that’s a fine reason to keep it in your week. Just don’t let anyone sell it as a cure.

Questions readers ask

The bottom line

Contrast therapy has deep roots and a modest record. Alternating hot and cold water eases soreness after hard exercise a little more than resting does, but no better than a plain cold plunge, stretching or compression. The trials behind it are small and easy to bias.

Its strongest effect is on your circulation: a fast rise and fall in heart rate and blood pressure that can be risky for a vulnerable heart. If you enjoy it, keep sessions short and sober, ease into the cold, and never go head-first. If you have heart disease, blood pressure problems or are pregnant, talk with a clinician before you start.

Related reading

• A cold plunge eases soreness but can shrink your muscle gains
• The famous sauna longevity study used Finnish saunas, not infrared cabins
• The symptoms that mean call 911 now
• Most health products aren’t scams, but many just haven’t been proven
• Six questions to ask before you buy anything for your health

Sources

1. Walsh JJ. “Sebastian Kneipp.” The Catholic Encyclopedia, Robert Appleton Company, 1910 (New Advent edition). newadvent.org
2. Jarry J. “Sweating Out the Hype Over the Finnish Sauna.” McGill University Office for Science and Society, 2021. mcgill.ca
3. University of Copenhagen, Faculty of Health and Medical Sciences. “Winter-Swimming Scandinavian Men Can Teach Us How the Body Adapts to Extreme Heat and Cold.” University of Copenhagen, 2021. healthsciences.ku.dk
4. Bieuzen F, Bleakley CM, Costello JT. “Contrast Water Therapy and Exercise Induced Muscle Damage: A Systematic Review and Meta-Analysis.” PLoS ONE, 2013. eprints.qut.edu.au
5. Chen R, Ma X, Ma X, Cui C. “The Effects of Hydrotherapy and Cryotherapy on Recovery From Acute Post-Exercise Induced Muscle Damage: A Network Meta-Analysis.” BMC Musculoskeletal Disorders, 2024. pubmed.ncbi.nlm.nih.gov
6. Laukkanen JA, Laukkanen T, Kunutsor SK. “Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence.” Mayo Clinic Proceedings, 2018. espalibrary.eu
7. National Center for Cold Water Safety. “Cold Shock.” National Center for Cold Water Safety. coldwatersafety.org
8. Podstawski R, Borysławski K, Clark CCT, Laukkanen JA, Gronek P. “The Effect of 16-Minute Thermal Stress and 2-Minute Cold Water Immersion on the Physiological Parameters of Young Sedentary Men.” Montenegrin Journal of Sports Science and Medicine, 2020. doi.org
9. Ravanelli N, Casasola W, English T, Edwards KM, Jay O. “Heat Stress and Fetal Risk. Environmental Limits for Exercise and Passive Heat Stress During Pregnancy: A Systematic Review With Best Evidence Synthesis.” British Journal of Sports Medicine, 2019. pubmed.ncbi.nlm.nih.gov
10. Buijze GA, Sierevelt IN, van der Heijden BCJM, Dijkgraaf MG, Frings-Dresen MHW. “The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial.” PLoS ONE, 2016. journals.plos.org
11. University of Exeter. “Mums-to-be Can Exercise in Warm Weather and Use Saunas Without Getting Too Hot.” University of Exeter news release, 2018. news-archive.exeter.ac.uk