Back to overview / Recover faster

Cold Therapy

Table of Contents

Why cold therapy works: the hormesis principle
What happens in your body during cold exposure
Cold therapy for mood and mental health
Cold exposure and aging
Protocols: how to start safely

Why cold therapy works: the hormesis principle

Cold therapy is the deliberate use of cold temperatures to trigger beneficial stress responses in the body. The concept behind it is hormesis: a mild stressor provokes adaptive changes that leave you more resilient than before. Humans have practiced this for millennia, from Nordic ice bathing to Kneipp hydrotherapy, but modern research now explains what's happening at a molecular level. Cold exposure activates survival pathways that improve immune function, metabolism, cardiovascular health, and brain chemistry.

What happens in your body during cold exposure

Immersion in cold water (typically 1-15 degrees Celsius) triggers immediate sympathetic nervous system activation. The most significant measurable effect is a surge in norepinephrine: the landmark study by Sramek et al. (2000) found that immersion at 14 degrees Celsius increased plasma norepinephrine by 530% and dopamine by 250% ^[1]. This catecholamine release improves mood, sharpens focus, and lasts for hours after exposure. Norepinephrine also suppresses pro-inflammatory cytokines TNF-alpha and IL-6, producing a measurable anti-inflammatory effect.

Brown adipose tissue (BAT), the metabolically active fat that generates heat through uncoupled mitochondrial respiration, gets activated and expanded through regular cold exposure. Van der Lans et al. (2013) showed that just ten days of cold acclimation increased BAT activity and nonshivering thermogenesis in healthy adults ^[3]. Soberg et al. (2021) found that regular winter swimmers had enhanced cold-induced thermogenesis compared to controls, with direct implications for metabolic health and energy expenditure ^[8].

Immune modulation and cardiovascular training

The Radboud University study by Kox et al. (2014) showed that practitioners trained in the Wim Hof Method could voluntarily activate their sympathetic nervous system when challenged with bacterial endotoxin. Cold-adapted subjects produced significantly higher anti-inflammatory IL-10 and lower pro-inflammatory cytokines ^[2]. Buijze et al. (2016) found in a randomized trial of 3,018 participants that routine cold showers led to a 29% reduction in self-reported sickness absence from work ^[4]. Repeated cold water immersion also trains the cardiovascular system through vasoconstriction-vasodilation cycles that maintain vascular elasticity, functioning much like a workout for your blood vessels.

Cold therapy for mood and mental health

The 250% dopamine increase from cold immersion ^[1] is comparable to what certain medications aim to achieve. Dopamine and norepinephrine are both reduced in depression, and cold exposure raises both simultaneously. A 2024 review in the Journal of Neuropsychiatry and Clinical Neurosciences described cold-water immersion as a form of "neurohormesis" with potential applications in clinical neuroscience ^[9]. A Frontiers in Psychiatry protocol registered in 2025 is now conducting the first systematic review and meta-analysis on cold-water exposure and mental health ^[10]. The evidence is still early-stage, and most studies are small or lack adequate controls, but the neurochemical rationale is solid and aligns with known mechanisms of antidepressant action.

Cold exposure and aging

A 2025 review in Life Sciences examined whether cold exposure can counteract aging processes. The authors found evidence that cold activates multiple longevity-relevant pathways: it upregulates heat shock proteins, strengthens antioxidant defenses, stimulates autophagy, and enhances mitochondrial biogenesis ^[11]. A separate 2025 review in Aging and Disease described cold water therapy as an "untapped potential" lifestyle intervention for healthy aging, noting its effects on cardiometabolic risk factors and brown fat activation ^[12]. The Kelly et al. (2025) systematic review of 11 RCTs with 3,177 participants found significant benefits for health and wellbeing, though the authors noted substantial heterogeneity across trials ^[7].

Protocols: how to start safely

Effective cold therapy doesn't require extremes. Research suggests that roughly 11 minutes per week distributed across 2-4 sessions delivers reliable benefits. Start with cold shower finishes: 30-60 seconds of cold water at the end of a warm shower. This captures most of the norepinephrine and mood effects without requiring a dedicated cold plunge setup. Over weeks, extend the duration and lower the temperature gradually.

Full immersion in a cold plunge pool or natural water (10-15 degrees Celsius for 2-5 minutes) provides more complete exposure. For exercise recovery, a 2025 network meta-analysis found that medium-temperature immersion (11-15 degrees Celsius for 10-15 minutes) offers the best balance between effectiveness and tolerability ^[13].

What to watch out for

Avoid cold immersion within 4-6 hours after strength training if hypertrophy is your goal. The Pinero et al. (2024) meta-analysis confirmed that post-exercise cold water immersion attenuates muscle growth ^[5]
Never practice cold water immersion alone in open water. Cold shock can cause involuntary gasping, cardiac arrhythmias, and motor control loss within seconds
People with cardiovascular disease, uncontrolled hypertension, Raynaud phenomenon, or cold urticaria must consult a physician first
Focus on controlled breathing during exposure. Slow, deliberate breaths reduce the cold shock response and, according to Kox et al. (2014), amplify the anti-inflammatory benefits ^[2]

References

Use cold exposure as a mood booster

Cold water immersion raises dopamine by 250% and norepinephrine by 530%, both of which stay elevated for hours. If you're feeling sluggish or low, a 1-2 minute cold shower can produce a measurable shift in alertness and mood that rivals a cup of coffee.

psychiatryonline.org

End your cold exposure on cold, not warm

Research from Soberg et al. suggests ending on cold rather than rewarming with a hot shower afterward. Letting your body reheat itself through its own thermogenesis maximizes brown fat activation and caloric expenditure. Towel off and let shivering do the work.

pubmed.ncbi.nlm.nih.gov

For muscle recovery, use moderate cold

A 2025 network meta-analysis found that water at 11-15 degrees Celsius for 10-15 minutes works best for reducing muscle soreness after exercise. Colder isn't necessarily better. This moderate range provides effective cooling without excessive discomfort or risk of tissue damage.

pmc.ncbi.nlm.nih.gov

Start with cold shower finishes, not full plunges

End your regular warm shower with 30 to 60 seconds of cold water. This captures most of the norepinephrine and mood benefits documented by Sramek et al. without requiring a dedicated cold plunge setup. Gradually extend the duration over several weeks as your tolerance builds.

Cold exposure basics

A 2-3 minute cold shower at 15°C triggers a 200-300% norepinephrine increase lasting hours. Start with 30 seconds cold at the end of your normal shower.

Time cold exposure away from strength training

If muscle growth is your priority, separate cold immersion from resistance training by at least four to six hours. The Pinero et al. (2024) meta-analysis found that post-exercise cold water immersion likely attenuates hypertrophy adaptations. Use cold sessions on rest days or well before your workout for the best of both worlds.

Cold plunge benefits

Cold water immersion (10-15°C for 2-5 min) reduces muscle soreness and inflammation. Avoid immediately after strength training if hypertrophy is your goal — it may blunt the adaptive response.

Aim for 11 minutes of cold exposure per week

Research suggests that distributing approximately 11 minutes of total cold exposure across two to four sessions per week delivers robust benefits for mood, brown fat activation, and norepinephrine release. You do not need marathon sessions in ice water — consistency at moderate cold temperatures matters more than extreme cold or long durations.

Focus on controlled breathing during cold exposure

When you enter cold water, resist the urge to hyperventilate. Slow, deliberate breathing activates the parasympathetic nervous system and reduces the cold shock response. The Kox et al. (2014) study showed that combining controlled breathing with cold exposure amplified anti-inflammatory benefits beyond cold exposure alone.

10.

Never practice cold water immersion alone in open water

Cold shock can trigger involuntary gasping, cardiac arrhythmias, and loss of motor control within seconds of immersion. Always have a partner present, especially in open water settings like lakes or rivers. Start in controlled environments such as a cold shower or supervised plunge pool, and build experience before attempting outdoor cold water exposure.

Can cold therapy help with depression and anxiety?

Cold water immersion raises dopamine by 250% and norepinephrine by 530%, both neurotransmitters that are reduced in depression. A 2024 review in the Journal of Neuropsychiatry described this as "neurohormesis" with potential clinical applications. Individual case studies and small feasibility trials have shown mood improvements, but large randomized controlled trials are still lacking. A systematic review protocol registered in 2025 aims to provide clearer answers. Cold exposure is not a replacement for professional mental health treatment, but it may be a useful complement.

Does cold therapy slow aging?

A 2025 review in Life Sciences found that cold exposure activates several longevity-relevant pathways: it upregulates heat shock proteins, strengthens antioxidant defenses, stimulates autophagy, and promotes mitochondrial biogenesis. Regular cold exposure also activates brown fat, which burns calories and improves metabolic health. These are all mechanisms associated with slower biological aging. However, most evidence comes from animal studies or small human trials, and no long-term human study has directly measured cold therapy's effect on biological age or lifespan.

Should I end on cold or warm after a cold plunge?

Ending on cold appears to be more effective. Research by Soberg et al. (2021) on winter swimmers found that letting the body rewarm itself through its own thermogenesis, rather than jumping into a hot shower, maximizes brown fat activation and energy expenditure. After your cold exposure, simply towel off and allow your body to generate its own heat. The shivering process is part of the benefit.

How cold does the water need to be for cold therapy benefits?

Most research uses water temperatures between 1 and 15 degrees Celsius. The landmark Sramek et al. study used 14 degrees Celsius and found a 530% increase in norepinephrine. You do not need near-freezing water to see benefits. Water at 10 to 15 degrees Celsius is sufficient for most people, and the key is that it feels uncomfortably cold but tolerable. Start at the warmer end and gradually lower the temperature as you adapt.

Does cold water immersion after exercise hurt muscle growth?

The evidence suggests it can. A 2024 meta-analysis by Pinero et al. in the European Journal of Sport Science found that post-exercise cold water immersion likely attenuates resistance training-induced hypertrophy. The anti-inflammatory response from cold exposure may blunt the inflammatory signaling needed to stimulate muscle protein synthesis. If muscle growth is your primary goal, separate cold exposure from strength training by at least four to six hours or use it on rest days.

What is brown fat and how does cold exposure activate it?

Brown adipose tissue is a metabolically active type of fat that generates heat through a process called nonshivering thermogenesis, using a mitochondrial protein called UCP1. Unlike white fat, which stores energy, brown fat burns calories to produce warmth. Cold exposure activates the sympathetic nervous system, releasing norepinephrine that stimulates brown fat cells. Van der Lans et al. (2013) showed that just ten days of cold acclimation increased brown fat activity in healthy adults, and Soberg et al. (2021) found enhanced cold-induced thermogenesis in regular winter swimmers.

Should I do cold plunges after every workout?

Not necessarily. Cold water immersion after strength training can blunt the hypertrophy response (muscle growth) by reducing inflammation that signals adaptation. Best practice: use cold plunges on rest days or after cardio/endurance work. If muscle growth is your primary goal, save cold exposure for recovery days. The anti-inflammatory benefits are real but timing matters.

Can cold showers really reduce sick days?

One large randomized controlled trial suggests they can. Buijze et al. (2016) studied 3,018 participants and found that a routine of finishing a warm shower with 30 to 90 seconds of cold water led to a 29 percent reduction in self-reported sickness absence from work. Interestingly, the cold showers did not reduce the actual number of days people felt ill, suggesting the benefit may come from improved resilience and energy rather than fewer infections.

Who should avoid cold therapy?

People with cardiovascular diseases, uncontrolled hypertension, Raynaud phenomenon, or cold urticaria should consult a physician before starting any cold exposure protocol. Cold immersion triggers significant cardiovascular stress, including spikes in heart rate and blood pressure. Additionally, the cold shock response can cause involuntary gasping and cardiac arrhythmias in unacclimatized individuals. Pregnant women and people with epilepsy should also seek medical advice before practicing cold immersion.