Does whole-body cryotherapy work? The evidence is strongest for pain

Whole-body cryotherapy - two to three minutes standing in a chamber of extremely cold dry air - works most consistently on pain, and least consistently on the biology it is sold on. Five studies covering 310 people with ankylosing spondylitis, a form of inflammatory arthritis that stiffens the spine, found less pain, better physical function and lower disease activity when cryotherapy was added to their usual medication [2]. The same pooled analysis found no change in C-reactive protein, a blood marker that rises when the body is inflamed [2]. Pain scores moved; the inflammation reading did not.

Chronic low back pain came out the same way. Forty-one adults did 20 sessions at minus 160 degrees Celsius over five weeks, and their pain and disability scores fell, with the drop in pain already measurable by the fourth session [4]. That study ran without a comparison group, so part of the improvement could be the ordinary waxing and waning of back pain.

In trained athletes the result reverses. Eleven endurance-trained men did hard interval running followed by either three minutes at minus 110 degrees or ordinary rest, and cryotherapy changed none of the seven blood markers measured - among them inflammation signals, a protein released by damaged muscle, and the stress hormone cortisol [7]. The authors concluded that the mechanism cryotherapy is supposed to work through may not be accurate [7]. A second crossover study in 11 endurance athletes found no effect on an adhesion molecule linked to exercise-induced muscle damage, though the same group's earlier work on those athletes had recorded less muscle soreness after cryotherapy [10]. Soreness is easier to shift than the blood chemistry underneath it.

Over six weeks, twice-weekly cryotherapy alongside a strength and endurance programme did not blunt gains in leg strength or barbell squat in 16 physically active men [15]. Adding cryotherapy made no difference to body fat compared with training alone, which is the closest thing in this evidence to a test of the weight-loss claim [15]. The cryotherapy group was also the only one that failed to improve its jump height [15].

In 15 healthy adults who used cryotherapy recreationally for around nine months, each session in the month before a blood test was associated with a reading about 0.14 milligrams per litre lower on high-sensitivity C-reactive protein, a more sensitive version of that same inflammation test, and the association held across the nine months [13]. There was no control group, and cholesterol and triglycerides did not change [13].

Two smaller trials looked past pain. Adults already taking medication for a depressive episode were given either 10 real sessions at minus 110 to minus 160 degrees or 10 fake ones at a much milder minus 50 degrees; 56 of the 92 people enrolled finished, and the real-cold group improved more on two standard depression questionnaires and on quality of life [6]. Self-reported sleep did not budge in that trial, while a crossover study in 17 female athletes found better measured sleep quality and less fatigue in the two weeks after ovulation [8].

The proposed explanation is that a sudden, extreme cold shock narrows blood vessels and damps down pain signalling, which is how reviews of its use in bone and joint medicine describe its pain-relieving and anti-inflammatory effects [3].

Some of that does show up in blood. Across 20 sessions in people with chronic back pain, a pro-inflammatory messenger called interleukin-2 fell while interleukin-10, a messenger that damps inflammation down, rose [4]. In healthy recreational users, the general inflammation reading dropped as sessions accumulated [13].

The antioxidant side has thinner support. After 20 sessions, men showed higher activity of catalase, an enzyme that breaks down hydrogen peroxide before it can damage cells [14].

Timing matters more than the marketing admits. A single session after hard exercise moved nothing at all in trained men [7], while the changes that do appear come from courses of 10 to 20 sessions in people who were inflamed or in pain to begin with [4], [6], [13]. That fits something which slowly shifts a chronically raised baseline, not something that speeds up recovery from one workout.

This field is under-powered. A review in the British Medical Bulletin concluded that the quality of studies on cryotherapy in clinical settings is generally low, and called for randomised trials with adequate sample sizes and longer follow-up [5]. The individual studies here enrolled 11, 15, 16, 17 and 41 people.

Two of the more encouraging results have no comparison group at all: the back-pain study [4] and the healthy-adult inflammation study [13]. Without one you cannot separate the cold from time passing, from attention, or from the belief that something is being done.

Protocols are not standardised. Sessions in these studies ran from 80 seconds to three minutes, at chamber temperatures anywhere from minus 10 to minus 160 degrees Celsius [2], [4]. Two clinics using the same word may not be selling the same thing.

The evidence does not apply to:

• anyone using cryotherapy for weight loss - the one trial that measured body fat found adding it to training changed nothing [15]
• anyone expecting it to slow ageing - the single study here that measured biological age gave cryotherapy alongside oxygen therapy, carbon-dioxide baths and other treatments at once, so nothing can be pinned on the cold [12]
• healthy people hoping for the pain results - most of the pain evidence comes from patients with diagnosed inflammatory disease [2], [3]
• women, in the recovery research - the athlete and training trials enrolled men only [7], [10], [15]

Reviews list frostbite and reduced muscle strength among the risks [3], and the training study found the cryotherapy group was the only one that did not gain explosive power [15]. Against that, the 41-patient course of 20 sessions recorded no adverse events [4]. Nothing in these papers tests whether cryotherapy affects how long people live.

Whole-body cryotherapy is a standard item on longevity clinic menus, usually listed next to red-light panels and NAD drips and sold as recovery or wellness rather than as a treatment. A first visit is short: you strip to underwear, cover the extremities most exposed to frostbite, and stand in the chamber for something in the range of 80 seconds to three minutes used across this research [2], [3]. Clinics normally screen for heart and circulation problems beforehand, since reviews note effects across the cardiovascular system [3].

What these papers would lead you to expect is modest and conditional. If you have an inflammatory pain condition and do a course of 10 to 20 sessions, the pain evidence is real, though the trials behind it are small [2], [4]. If you are healthy and after faster recovery from training, a single session following a hard workout changed nothing measurable in the men who were tested [7].