Cold plunges: what the studies measured

Do cold plunges work? Most studies of cold-water immersion measured one thing: muscle soreness after hard exercise. A 2012 Cochrane review of 17 small trials found less soreness over the next four days than with rest. The trials used water below 15 °C (59 °F). The reviewers rated the trials' quality low.

Other findings are smaller or mixed. In strength training, regular cold immersion after sessions blunted gains in muscle and strength in several trials. A 2025 review found lower stress 12 hours after immersion and better sleep in one small study, but no effect on mood. The research is Moderate for soreness after exercise and Early for the rest.

What counts as a cold plunge?

A cold plunge is sitting or standing in cold water, usually up to the waist or chest, for seconds to minutes. Athletes use ice baths after training. In Finland and other northern countries, people swim through holes cut in winter ice. Cold showers were the briefest exposure studied: 30 to 90 seconds in the main trial.

Researchers draw the line by temperature. The Cochrane review counted water below 15 °C as cold. A 2025 review in PLOS ONE included baths, plunges and showers at 7 to 15 °C (45 to 59 °F). Immersions lasted from 30 seconds to two hours.

Supporters describe cold water as a way to calm inflammation, lift mood and recover faster. Physiologists at the University of Portsmouth reviewed claims like these in 2017. They wrote that for some of them, "the supporting data remain at the level of anecdotal speculation."

What cold water does in the first minutes is well described. Sudden immersion triggers the cold shock response: a gasp, rapid breathing, a faster heart rate and a rise in blood pressure. A 2012 review by Michael Shattock and Michael Tipton in the Journal of Physiology sets out how this works.

What did the studies measure?

Soreness (Moderate). The 2012 Cochrane review pooled 17 trials with 366 people. Soreness was lower than with rest at 24, 48, 72 and 96 hours. Results varied between trials, and most did not watch for side effects. Cold water did no better than warm-water or hot-and-cold immersion. A 2016 meta-analysis of nine trials found cold water "slightly better than passive recovery." In a 2023 update of 44 studies, water temperature did not change the result.

Inflammation in muscle. A 2017 trial took muscle samples from nine active men after leg exercise. Ten minutes in 10 °C water was "no more effective" than 10 minutes of easy cycling at reducing inflammation in the muscle.

Strength training (Moderate). In a 2015 trial, 21 men did strength training twice a week for 12 weeks. After each session, they had either 10 minutes in cold water or 10 minutes of easy cycling. Muscle and strength grew more in the cycling group. A 2021 meta-analysis of eight studies found regular cold immersion lowered strength gains. It found no effect on endurance training. A 2019 trial in 16 men found muscle fiber growth blunted, but strength gains were similar.

Stress, sleep and wellbeing (Early). The 2025 PLOS ONE review pooled 11 trials with 3,177 people. Reported stress was lower 12 hours after immersion, but not at other times. Markers of inflammation rose right after immersion and an hour later. Sleep quality improved in one small study. Of the 3,177 people, 3,018 came from one cold-shower trial. The other studies enrolled only men.

Cold showers. That 2016 trial in the Netherlands enrolled 3,018 adults. Their warm showers ended with 30, 60 or 90 seconds of cold water. They did this daily for 30 days. Self-reported sickness absence from work fell 29 percent compared with the control group. The number of days people were ill did not change.

Where do the claims go past the studies?

Cold plunges are often sold as a recovery tool for anyone who trains. The trials support less soreness. One trial in nine men found no better effect on muscle inflammation than easy cycling. For people training for strength, several trials found smaller gains.

Claims about mood and depression rest on very little. One case report describes a woman whose depression eased with weekly open-water swimming (BMJ Case Reports, 2018). A 2023 brain-scan study measured 33 adults before and after five minutes in 20 °C (68 °F) water. They reported feeling more alert and less distressed. That study had no separate control group.

Claims about immunity go further than the trials. A 2014 trial trained 12 healthy volunteers in cold exposure, breathing and meditation together, against 12 untrained controls. Afterwards, their immune response to an injected bacterial toxin was dampened. Cold's share cannot be separated from the rest. The shower trial found less time off work, not less illness.

What did the studies use?

These are the protocols the trials ran, reported here, not suggested.

• Soreness trials: mostly 10 to 15 °C (50 to 59 °F). Continuous immersions lasted 5 to 24 minutes, 12.6 minutes on average, after exercise.
• The 2015 strength trial: 10 °C (50 °F) for 10 minutes, legs in to the waist. Immersion began within five minutes of each session.
• The shower trial: the coldest tap water, 10 to 12 °C (50 to 54 °F). It ran for 30 to 90 seconds at the end of a warm shower.
• The 2025 review: 7 to 15 °C, at least chest-deep for the baths.
• A 2019 strength trial: 10 °C for 15 minutes after each session, three times a week for seven weeks.
• A 2017 inflammation trial: 10 °C for 10 minutes after one bout of leg exercise.
• The people: healthy adults. Apart from the large shower trial, which took adults aged 18 to 65, most trials enrolled young men. Trials excluded people with chronic illness or serious heart or lung disease.

What do the warnings say?

A 2017 review by University of Portsmouth physiologists describes cold water immersion as a precursor to drowning, cardiac arrest and hypothermia. The National Center for Cold Water Safety reports a study in 5 °C (41 °F) water. Average breath-holding fell from 45 to 9.5 seconds. Shattock and Tipton report heart rhythm disturbances in about 2 percent of head-out immersions. With the face under water and the breath held, the figure was 62 to 82 percent. Harvard Health reports that cold plunges are not advisable after heart disease, including rhythm problems such as atrial fibrillation. It adds peripheral artery disease and Raynaud's. The British Heart Foundation says people with a heart condition should talk to a doctor or nurse first. The CDC lists signs of hypothermia: shivering, exhaustion, confusion, fumbling hands, slurred speech and drowsiness.

Questions to Ask Your Doctor

• With my heart condition or blood pressure, is sudden cold-water immersion safe for me?
• Could the cold shock response trigger my heart rhythm problem?
• I have Raynaud's or poor circulation in my legs. Does that rule out cold plunges?
• Could any of my medicines change how my body handles cold water?
• Would cold-water immersion affect my recovery from an injury or surgery?

Questions People Ask

Is a cold shower the same as a cold plunge?

The studies treat them separately. The 2025 review required baths to reach at least chest level, and only one of its trials used showers. In the Dutch shower trial, 79 percent of people finished the 30 days. The most common side effect was a cold feeling that lasted afterwards, in the body or in the hands and feet.

Is the 1-10-1 rule reliable?

The rule says a person in cold water has one minute to control breathing and ten minutes of useful movement. It gives an hour before hypothermia causes unconsciousness. The National Center for Cold Water Safety calls it misleading. It says breathing control can take longer, strength fades from the start, and people drown long before hypothermia sets in.

Is cold water safe in pregnancy?

According to the University of Portsmouth's 2025 summary of its review, researchers found only six published studies. Their consensus advice was that only women who swam in cold water regularly before pregnancy continue. They also advised never swimming alone, and avoiding it with high or very low blood pressure. Their main finding was the lack of evidence.

Does a cold plunge burn fat?

Cold raises energy use while it lasts. In a 2000 lab study, young men sat in 14 °C (57 °F) water for an hour. Their metabolic rate rose 350 percent. A 2021 study compared seven or eight experienced winter-swimming men with eight non-swimmers. In the cold, the swimmers' heat production rose more, but their brown fat took up glucose about the same. The authors could not conclude that winter swimming caused the differences.

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The Healing Spot reports published research for general information. It is not medical advice and does not replace a doctor, who knows your history. Talk to a qualified clinician before you start, stop or change any treatment, supplement or practice. If you think you may have a medical emergency, call 911 or your local emergency number.