Do cold plunges work? What the evidence shows

Stress, sleep and sick days: the 2025 meta-analysis

The recovery benefit is the best-supported claim, and most of its main findings were rated moderate or high certainty³. Evidence for stress, sleep, immunity and fat loss comes mostly from small, short studies, often in men only^{1, 6}. One large cold-shower trial cut self-reported sick days but not days of illness, and its participants couldn’t be blinded². People with heart or circulation problems were largely left out of the trials^{1, 2}.

The broadest look at cold-water immersion for everyday health is a 2025 systematic review and meta-analysis in PLOS ONE. It included 11 randomized trials with 3,177 healthy adults, all using cold-water immersion except one that used cold showers¹. Water was 7 to 15 °C (about 45 to 59 °F), and exposures lasted anywhere from 30 seconds to two hours¹. People with chronic illness or injuries were excluded, as were high-level athletes¹. Every trial except the shower trial enrolled only men¹.

Pooled stress measures were lower 12 hours after immersion (standardized mean difference −1.00)¹. They weren’t lower immediately afterward or at 1, 24 or 48 hours¹. Inflammation markers rose right after immersion and an hour later, while pooled immune measures didn’t change¹. Sleep, mood and quality of life were reported study by study rather than pooled¹.

The often-quoted 29% drop in sick days comes from a single trial in the review. It randomized 3,018 working Dutch adults to either shower as usual or end their shower with a burst of cold². The cold groups used the coldest available water, roughly 10 to 12 °C². The burst lasted 30, 60 or 90 seconds². They kept it up for 30 consecutive days².

Self-reported sickness absence fell (incidence rate ratio 0.71), but the number of days people felt ill didn’t². The length of the cold burst made no difference². Participants couldn’t be blinded, so expectation effects can’t be ruled out².

The review’s authors graded the evidence B for stress and inflammation and D (inconclusive) for immunity¹. They flagged small samples and noted that six of the 11 trials tested a single session¹. No trial except the shower trial included women¹. In five trials, immersion followed exercise, which mixes up cold effects with recovery¹.

Does a cold plunge help recovery after hard exercise?

Short-term recovery is where cold-water immersion has its best evidence. A 2022 Sports Medicine meta-analysis pooled 52 studies of physically active people³. After a single bout of strenuous exercise, they either sat in cold water or simply rested³.

At 24 hours after high-intensity exercise, immersion reduced muscle soreness (standardized mean difference −0.89) and the muscle-damage marker creatine kinase (−0.85)³. It also improved perceived recovery (0.66) and muscular power (0.22)³. After eccentric exercise, where muscles lengthen under load, the only consistent 24-hour benefit was a small gain in power (0.34)³. Soreness eased later, at 48 to 96 hours³. Strength, endurance and flexibility didn’t recover faster than with rest³.

After high-intensity exercise, shorter and colder immersions were linked to larger effects on creatine kinase and endurance³. Water temperature and time in the water made no significant difference to soreness, power or perceived recovery³. The authors rated most main findings moderate or high certainty³. They also noted that only 11 of the 52 studies adequately reported how participants were randomized³.

Hot-cold contrast routines have far less direct evidence in the studies reviewed here. The cold-shower trial was itself a contrast routine. Participants showered as warm as they liked, then finished with 30 to 90 seconds of cold². The recovery meta-analysis compared cold water with resting, not with alternating hot and cold³. So it doesn’t show whether adding heat improves or dilutes the effect³.

Does cold water after lifting blunt muscle gains?

Feeling recovered isn’t the same as adapting to training. A 2021 meta-analysis of eight studies looked at regular cold-water immersion used alongside a training program⁴. Immersion reduced gains in one-repetition maximum, maximum isometric strength and strength endurance (standardized mean difference −0.60, 95% CI −0.87 to −0.33)⁴. It also reduced gains in ballistic efforts (−0.61, 95% CI −1.11 to −0.11)⁴. It didn’t change improvements in maximal aerobic power or time-trial performance after endurance training⁴.

A 2024 meta-analysis of eight studies looked at muscle size when cold-water immersion followed resistance training⁵. Training alone produced more muscle growth than training followed by immersion (effect size −0.22, 95% credible interval −0.47 to 0.04)⁵. There was about a 96% probability that the cold-water groups grew less⁵. Training status didn’t appear to change the result⁵. The authors rated the included studies fair to poor in quality and urged caution⁵.

In these studies, routine plunges right after lifting worked against strength and muscle gains, while endurance adaptations looked unaffected^{4, 5}. The trials applied cold soon after training⁵. They don’t show whether plunging hours later or on rest days avoids the effect⁵.

Brown fat and metabolism

Cold activates brown adipose tissue, a type of fat that burns energy to make heat. In a small 2013 study, 17 healthy young adults spent 10 days acclimating to mild cold⁷. Each day they were exposed to 15 to 16 °C for up to six hours⁷. Brown fat activity rose⁷. So did nonshivering thermogenesis, the extra heat produced in mild cold without shivering, which went from 10.8% to 17.8%⁷.

A 2015 study put eight people with type 2 diabetes through 10 days of cold acclimation at 14 to 15 °C⁸. Their peripheral insulin sensitivity rose by about 43%⁸. Brown fat glucose uptake rose only slightly⁸. In skeletal muscle, basal GLUT4 translocation (the movement of glucose transporters to the cell surface) rose markedly⁸. With eight participants, this is an early signal, not evidence that cold exposure treats diabetes⁸.

The 2013 study used hours a day in a cold room, not minutes in water⁷. A 2022 review looked at 104 studies of voluntary cold-water exposure, such as winter swimming and ice bathing⁶. It concluded that this kind of exposure may reduce or alter body fat and improve insulin sensitivity⁶. Most of those studies were small, often included only one sex and used different water temperatures⁶. The authors also said it’s unclear whether winter swimmers as a group are simply healthier to begin with⁶.

What the evidence doesn’t show

Several popular claims go further than the studies behind them.

• Longer life or disease prevention. Six of the 11 trials in the 2025 meta-analysis tested a single immersion¹. The longest followed people for 90 days, so none measured long-term health^{1, 2}.
• Stronger immunity. Pooled immune markers didn’t change¹. The cold-shower trial found fewer self-reported sick days but not fewer days of illness².
• Better mood. The 2025 meta-analysis found no mood benefit in the one study that measured it¹.
• Faster strength recovery. Strength didn’t return faster after immersion than after rest³.
• Meaningful fat loss from home plunges. The 2013 brown-fat study used hours of daily cold in a cold room, not short plunges⁷. The 2022 review found only that cold water may reduce or alter body fat, and most of its studies were small⁶.
• Results that apply to everyone. Every trial in the 2025 meta-analysis except the shower trial enrolled only men¹. People with chronic illness were excluded¹.

Is cold plunging safe? Cold shock, heart rhythm and Raynaud’s

Sudden immersion in cold water triggers the cold shock response. In the first seconds, breathing becomes rapid and hard to control⁹. Heart rate, blood pressure and cardiac output rise quickly⁹. A 2020 narrative review of cold-water swimming calls this initial shock and loss of breathing control the point of greatest drowning risk⁹. It also notes that very little inhaled water is needed to start the drowning process⁹.

The same review links some deaths to heart-rhythm disturbances⁹. These come from the body’s competing sympathetic and vagal reactions, sometimes called autonomic conflict⁹. The review says people with known or undiagnosed heart disease are more likely to have them⁹. It names coronary artery disease, long QT syndrome and a thickened heart muscle as predisposing factors⁹. It covers open-water swimming rather than home plunges, but it warns that even very experienced ice swimmers face a risk of death⁹.

The trials in the 2025 meta-analysis enrolled healthy adults and excluded people with chronic illness¹. The shower trial also excluded people with significant heart or lung disease². So they say little about risk for people with heart conditions, high blood pressure or circulation problems such as Raynaud’s phenomenon^{1, 2}.

• Don’t plunge alone, and keep your head above the water. The first moments of cold shock, when breathing is hard to control, carry the greatest drowning risk⁹. The review says cold-water swimming should be done only with appropriate supervision⁹.
• Heart and circulation problems: talk with a clinician who knows your health before trying cold immersion. The 2025 meta-analysis trials excluded people with chronic illness, and the shower trial excluded people with significant heart or lung disease^{1, 2}. That leaves little safety evidence if you have a heart condition, high blood pressure, Raynaud’s phenomenon or another circulation problem^{1, 2}. People with heart disease are more prone to cold-related rhythm disturbances⁹.
• Side effects in healthy adults: in the cold-shower trial, no serious adverse events were judged related to the showers². The most common related complaint was a lingering feeling of cold in the body, hands or feet². Three participants reported Raynaud’s phenomenon². Those were 30- to 90-second showers, not full-body plunges².

What to look for in a home cold plunge

If you decide to buy, match the hardware to the evidence and to your space. The trials in the 2025 meta-analysis used water between 7 and 15 °C (about 45 to 59 °F)¹. In the recovery meta-analysis, colder, shorter sessions were linked to larger effects on creatine kinase and endurance, but not on soreness³. No study here shows that a home plunge improves long-term health.

• Chiller range: check the lowest temperature the unit is rated to reach and the ambient conditions that rating assumes. If you want hot-cold sessions, check whether it can also heat.
• Sanitation: ask how the water is kept clean (filtration plus ozone, UV or chemical sanitizer). Find out how often filters need replacing, what they cost and how often the maker says to change the water.
• Electrical needs: check the voltage and amperage, and whether it needs a dedicated circuit or ground-fault (GFCI) protection. Look for the stated running watts so you can estimate electricity cost. Have a licensed electrician confirm the circuit.
• Safety and fit: look for a lid that locks, a non-slip floor or step and an easy way to drain it. Check its weight when full, and make sure its indoor or outdoor rating suits where it will sit.

Sources

1. Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis PLOS ONE, 2025 · meta-analysis
2. The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial PLOS ONE, 2016 · randomized trial
3. Impact of Cold-Water Immersion Compared with Passive Recovery Following a Single Bout of Strenuous Exercise on Athletic Performance in Physically Active Participants: A Systematic Review with Meta-analysis and Meta-regression Sports Medicine, 2022 · meta-analysis
4. The Effects of Regular Cold-Water Immersion Use on Training-Induced Changes in Strength and Endurance Performance: A Systematic Review with Meta-Analysis Sports Medicine, 2021 · meta-analysis
5. Throwing cold water on muscle growth: A systematic review with meta-analysis of the effects of postexercise cold water immersion on resistance training-induced hypertrophy European Journal of Sport Science, 2024 · meta-analysis
6. Health effects of voluntary exposure to cold water – a continuing subject of debate International Journal of Circumpolar Health, 2022
7. Cold acclimation recruits human brown fat and increases nonshivering thermogenesis Journal of Clinical Investigation, 2013
8. Short-term cold acclimation improves insulin sensitivity in patients with type 2 diabetes mellitus Nature Medicine, 2015
9. Cold Water Swimming—Benefits and Risks: A Narrative Review International Journal of Environmental Research and Public Health, 2020