Ice Bath / Cold Plunge

A pooled analysis of randomized trials found lower IL-6 immediately after exercise with cold-water immersion. Findings differ across analyses: a pooled analysis of human studies found no significant reduction in IL-6, while an RCT involving 22 people reported higher IL-10 after cold-water immersion than after resistance training and rest.

In an RCT involving 15 healthy people, thermal-sensation scores during the intervention were lower with cold-water immersion than with control, on a scale from 0 (unbearably cold) to 8 (unbearably hot). Another RCT involving 11 people also reported lower thermal-sensation scores in the cool condition, which participants rated as more comfortable.

In a study summarized in a review, all winter swimmers who reported rheumatism, fibromyalgia, or asthma said that winter swimming relieved their pain. These were participants’ reports, rather than a measured treatment effect.

A randomized trial of 16 reported faster recovery after MMR than PR. During the second half, perceived exertion was lower in COOL than CON in a randomized trial of 11 (p < 0.05), while a randomized trial of 8 found similar post-recovery exertion after CWI and PR (8.5 ± 2.7 vs 9 ± 3.4; ES 0.16).

A review involving 225 healthy people found varied balance results: some studies suggested improvement, while others found no effect. Overall, the review described more positive than negative findings, but noted that results were contradictory.

A review suggested that cold-water immersion may reduce or transform adipose tissue and may improve insulin sensitivity. These are reported as possible effects, rather than a quantified change in body composition.

Two RCTs reported reduced stress, including one involving 12 people that found a large effect. In contrast, a pooled analysis of randomized trials involving 3,177 people detected no significant stress effects immediately or at 1 hour, 24 hours, or 48 hours after exposure.

An RCT involving 76 people reported a decrease in anxiety scores, and a separate study involving 33 people found lower negative-affect scores after cold-water immersion. A pooled analysis involving 115 people found little evidence of a consistent association with anxiety symptoms, so the findings are mixed.

In one RCT involving 24 people, the cold-water immersion group increased barbell load from 94.5 ± 18.1 kg to 98.0 ± 18.7 kg between sets. However, a pooled analysis of human studies found no significant difference in muscular strength gains between cold-water immersion and control.

A review reported improved mood among winter swimmers in a questionnaire-based study, while a pooled analysis of randomized trials involving 20 people found no significant difference in mood between cold-water immersion and passive recovery. The findings therefore do not point consistently to a mood benefit.

In a trial of 76 participants with gout, joint mobility scores improved compared with pre-intervention and control. This finding applies to people with gout, not necessarily to joint health in general.

In a trial of 30 healthy participants, muscle oxygen consumption during isokinetic contractions increased after training with cold-water immersion. A separate trial of 19 participants questioned whether post-exercise immersion promotes mitochondrial biogenesis or endurance performance, so the findings are not consistent.

In an RCT involving 18 people, straight-leg-raise results were more favorable in the cold-water immersion group from the second to fifth day after eccentric contraction testing; on the second day, results were 86.3% ± 1.1% versus 78.8% ± 1.1%. A separate RCT involving 50 people found no significant differences between groups for other outcomes.

In one trial of 12 people, mean arterial pressure was reduced with cold-water immersion (MD -12 mmHg [-17, -8]), but the study described its findings as inconclusive because of methodological limitations. A trial of 28 people found no significant treatment effect or time-by-treatment interaction for mean arterial pressure.

In a trial of 20 healthy participants, the proportion classified as desaturators in the cold-water immersion group fell from 30% to 0% between period1 and period2; in the no-immersion group, it changed from 50% to 90%.

In a 2023 randomized trial of 12 healthy participants, heart rate fell by 4 bpm with CWI (95% CI −7 to −2 bpm), while the control group showed no change.

A 2023 review reported no changes in body weight, BMI, fat mass or fat-free mass, with waist circumference decreasing only in men. A 2024 cohort of 65 found visceral fat did not change significantly (MD 0.07 mm).

A 15-week randomized trial of 40 found body mass and fat-free mass increased similarly across all groups (~ 2 kg; time effect: p < 0.001), so it did not support a specific muscle-mass benefit.

Acute cold-water immersion, especially when a large surface area is exposed, is described as triggering a temporary increase in growth hormone secretion through sympathetic activation and cold-induced thermogenesis.

Cold stress may promote cellular cleanup by activating AMPK and suppressing mTOR pathways. The relevance to people remains indirect, with the proposed effect inferred mainly from animal and mechanistic studies.

Immersion in 14°C water is reported to raise plasma dopamine concentrations by approximately 250%. This acute response is described as contributing to mood and arousal effects of cold exposure.

A 2021 systematic review of randomized and non-randomized human studies found no effect on reasoning, so studies did not support this cognitive benefit.

Studies did not support a general blood-flow improvement. One RCT involving 21 people found Qc was higher only at 30 sec (p<0.001, d=0.84) and 4 min (p=0.048, d=0.55).

Studies did not support improved vagal tone. A 2025 cross-sectional study of 55 people found a 59 ± 19 beats decrease during the initial 25 s of facial immersion, compared with a 7 ± 23 beats reduction during the first 25 s of immersion in water (p < 0.001).

Studies did not support an alertness benefit. One quasi-experimental study of 29 people found that groups tended to complete the DAT faster during cold-water immersion than at baseline (95.5 s at baseline versus 69.16 s during immersion; V = 21, p = 0.035).

Repeated cold exposure is described as producing habituation to the cold-shock response and increasing tolerance to cold pain via reduced sympathetic reactivity and endogenous opioid release, as observed in regular cold-water swimmers.

The studies did not support a cellular-energy benefit from regular cold-water immersion: in a trial of 19 participants, regular immersion had no effect on the measured cellular markers, although a single sprint-interval training session increased them.

A randomized trial of 30 did not support a physical-function benefit; it assessed pain, triple-hop distance, extensor peak torque and blood creatine kinase before and after a run, after the intervention, and 24 hours after the run.

Studies did not support improved memory; a 2021 review found no effect on reasoning.

Studies did not support improved proprioception; a trial of 20 people found no significant effects at 55°, 90° or 125° (cold-water immersion–passive recovery at 55°: B=0.06, 95% CI −4.66 to 4.78 degrees).

A randomized trial of 12 healthy participants observed no changes in testosterone following cold-water immersion, so this finding does not support a testosterone increase.

Studies did not support improved spatial reasoning; a 2021 review found no effect of core cooling or superficial leg cooling on completion time or maze errors in computerized Hebb–Williams mazes.

A blood-glucose benefit has not been established in healthy participants.

Studies did not support a creativity benefit; one quasi-experimental study of 29 people found no relationship between peak heart rate and individual-within-group DAT scores (t(24) = 0.717, p = 0.48, r = 0.14, r^2 = 0.021).

A pooled analysis of randomized and non-randomized human studies found an anxiety estimate that was statistically inconclusive, with very wide confidence intervals; the authors found no robust signal.

A 2024 meta-analysis pooling randomized and non-randomized human studies did not support a reduction in chronic inflammation: the overall CRP result was uncertain (SMD -0.50, 95% CI -1.42 to 0.43), and IL-6 was not significant.

Pooled human studies reported prolonged sensations of cold in the body or extremities; another review reported hypothermia. The studies included people with Depression, Multiple Sclerosis and Rheumatoid Arthritis.

Reviews of randomized and non-randomized human studies describe a cold shock response with a sudden increase in heart rate, blood pressure, and breathing.

In a randomized trial of 29 people, immersion at 8 °C caused cold-related discomfort. Another randomized trial of 8 people reported pain or discomfort during the first minutes of immersion.

A pooled analysis of randomized and non-randomized human studies described hyperventilation as part of the cold-shock response on initial immersion. A separate pooled analysis of randomized trials linked severe cold with hyperventilation leading to blood acidosis; the studies were in healthy people.

A review of randomized and non-randomized human studies reported that acute exposure to cold water at 10 °C impaired working memory and attention.

In a cohort, all 110 participants assessed had T_hand below 15.0°C (mean ± SD lowest T_hand = 7.6 ± 2.5°C). A separate quasi-experimental study of 15 people reported tingling skin.

A review of human studies reported increases in peripheral catecholamine concentration and oxidative stress, with a possible increase in free-radical-species formation. In a trial of 34 healthy participants, phospho-NF-κB expression increased after TWI and CWI but remained stable after HWI.

In an RCT involving 9 healthy participants, post-immersion maximal force was lower at 23 °C than at 26 and 34 °C. A separate study of 35 participants found lateral gastrocnemius peak RMS was 33.38% lower after immersion and remained lower through 30 minutes.

A cohort study recorded isolated ventricular extrasystoles, and a separate study recorded ectopic beats during immersion. These findings describe observed rhythm disturbances rather than how often they occur.

A meta-analysis of randomized trials reported loss of consciousness or death in extreme cold situations. Another review associated decreased cerebral blood flow velocity with disorientation and loss of consciousness.

A meta-analysis of randomized trials reported discomfort and muscle tightness from low-temperature immersion.

A review of randomized and non-randomized human studies reported headache or dizziness in connection with cold-water immersion.

A review reported temporary neural responses associated with short-term instability; over the long term, those responses were described as helping improve stability and control.

A review of randomized and non-randomized human studies reported delirium in mild hypothermia.

An RCT involving 34 healthy participants reported unusual muscle cramps between 24 and 48 h follow-up.

A pooled review of randomized trials found that cold-water immersion reduced anaerobic average power by 2.4% in healthy participants.

A 2024 cohort study of 65 healthy participants found a 0.59 mm increase in subcutaneous fat. This finding concerns measured fat thickness rather than overall body weight.

Shivering is a thermoregulatory response; persistent or intense shivering indicates excessive cold stress and the need to exit and rewarm.

Cold-induced numbness, impaired dexterity and reduced coordination can increase the risk of slips, an unsafe exit or accidental submersion.

Cold water immersion can shift blood centrally through peripheral vasoconstriction, suppressing ADH and triggering diuresis. This can lead to dehydration if fluids are not replaced after immersion.

Long or very cold immersion can chill nerves near the skin of the hands and feet enough to cause numbness and, rarely, lasting non-freezing cold injury to those nerves.

In people with Cold Urticaria, cold water can trigger histamine release from skin mast cells, causing hives, redness and itching; whole-body immersion can make the reaction severe.

A review described decreased fatigue resistance following resistance-training interventions lasting 4–12 weeks.

One trial in 18 healthy participants found that pressure pain threshold scores in the cold-water immersion group first increased, then fell from 4.2 to 1.5 by Post48 (MD -2.5 kgf; p = 0.024).

Authors of two cross-sectional studies listed asthma or cold-induced asthma as a contraindication to polar plunging or cold-water immersion. One explicitly noted that cold-induced asthma was not empirically tested in the study.

Authors of two cross-sectional studies listed cold-induced urticaria as a contraindication to polar plunging or cold-water immersion. One explicitly noted that this contraindication was not empirically tested.

Authors listed epilepsy as a contraindication to polar plunging and cold-water immersion; one also noted that the hyperventilation involved in the STP could induce a seizure. This was a stated concern, not an empirical test of seizure risk.

A 2012 trial excluded 20 people with Raynaud’s disease before cold-water exposure, and a 2025 cross-sectional study listed it as a peripheral vascular contraindication to polar plunging. Cold hypersensitivity was checked through medical history and examination; these findings describe screening and precaution, not observed harm from exposure.

Authors of a cross-sectional study listed aneurysms as a contraindication to cold-water immersion, but did not empirically test this concern.

A case series described 9 women who developed transient global amnesia during or immediately after cold-water sea swimming; all recovered within 24 hours, and no further episodes were reported during follow-up. The report describes these events but does not establish how often they occur.

Cold-induced narrowing of blood vessels can promote sickling and precipitate a vaso-occlusive crisis, particularly with prolonged or intense exposure.

During early recovery after a heart attack, cold exposure can cause a sudden sympathetic surge, blood-vessel narrowing, blood-pressure changes, and increased oxygen demand by the heart, potentially provoking ischemia or an arrhythmia.

Marked loss of protective sensation can make it harder to detect excessive cold, tissue injury, or prolonged exposure, increasing the risk of cold injury.

With active muscle breakdown, cold-induced narrowing of blood vessels may reduce kidney blood flow and worsen kidney injury caused by myoglobin.

With advanced or symptomatic limb ischemia, cold-induced narrowing of blood vessels can further reduce blood flow to the limbs, potentially worsening ischemic pain or causing tissue injury.

Prolonged drops in core temperature during an ice bath may trigger uterine blood-vessel narrowing and reduce placental blood flow, posing a potential fetal risk, especially during first-trimester organ development.

During early recovery after an ischemic or hemorrhagic stroke, sudden cold-related blood-pressure spikes and autonomic instability may raise the risk of another cerebrovascular event.

An active fever or systemic febrile illness can impair temperature regulation; cold immersion may provoke intense shivering and cardiovascular stress. This is different from supervised cooling for exertional heat stroke.

Impaired heat production in hypothyroidism may increase susceptibility to hypothermia during cold exposure, including with mild protocols.

Sudden cold immersion can trigger a stress response and narrow blood vessels, sharply raising blood pressure and heart rate. One cold-water immersion study also excluded people taking prescription medication for hypertension or other drugs that could affect blood-vessel responses.

In a mouse model, acute cold-water immersion with restraint (10°C water, 1 h) caused intestinal mucosal injury, increased permeability, elevated TNF-α and reduced gut microbiota diversity. This animal finding does not establish the effect in people with Leaky Gut Syndrome.

The concern described is that cold air can trigger airway narrowing and increase airway resistance, worsening COPD.

Cold-induced narrowing of blood vessels increases the heart’s workload and the resistance it pumps against, which may worsen heart failure.

Cold exposure may prolong the QT interval, increasing the risk of torsades de pointes in people with Long QT syndrome.

Cold-induced shivering raises energy demand, which can deplete already limited energy stores in malnutrition.

Cold-induced narrowing of blood vessels in the lungs can raise pulmonary artery pressure and worsen pulmonary hypertension.

Cold-induced narrowing of blood vessels may reduce blood flow to surgical sites, potentially delaying healing and increasing infection risk.