Cold procedures: cryotherapy and ice baths

Ice baths and whole-body cryotherapy chambers have become a symbol of ‘professional’ recovery: photos of athletes in barrels of ice have spread across all social networks. Yet cold is a double-edged tool: it reduces pain and the feeling of fatigue, but can weaken the adaptations to strength training. The editorial team looked into when cold is appropriate and when it is better to forgo it.

Types of cold procedures

‘Cold procedures’ in sport refers to several different methods. The most widespread and best studied is cold water immersion (CWI): the athlete sits in a bath or pool with water at a temperature of about 10–15 °C, usually up to the waist or chest.

Whole-body cryotherapy (WBC) is spending 2–4 minutes in a chamber with very cold dry air, the temperature of which can drop to −110 °C and lower. There are also ‘cryosaunas’ in which the head remains outside and cooling is provided by liquid nitrogen vapour.

Local methods — ice packs, cold compresses, cryomassage, sprays — are used mainly for acute injuries and for targeted pain relief. Contrast procedures alternate heat and cold.

Despite the outward similarity, these methods differ substantially in physical terms. Water removes heat about 25 times more effectively than air of the same temperature, so a bath with water at +10 °C cools the muscles more deeply than a brief stay in a cryochamber with air at −110 °C.

How cold affects the body

On immersion in cold water the vessels of the skin and surface tissues reflexively constrict, and blood flow in the limbs decreases. The hydrostatic pressure of the water additionally ‘squeezes’ fluid from the tissues of the legs into the central vessels. This is one of the likely reasons for the reduction of swelling after intense loads.

Cooling reduces the speed of nerve impulse conduction and the sensitivity of pain receptors. This is precisely what explains the quick pain-relieving effect of cold and the pleasant feeling of ‘fresh legs’ after a bath. The rate of metabolic processes in the cooled tissues also decreases.

Cold activates the sympathetic nervous system: the level of noradrenaline rises sharply, breathing and pulse quicken. The first seconds of immersion in very cold water cause the so-called cold shock — an involuntary deep inhalation and hyperventilation. In open water it is precisely this reaction that is a frequent cause of drowning.

Finally, cold inhibits inflammatory and anabolic signalling pathways in the muscle. In the short term this reduces pain and swelling, but in the long term it can interfere with the very adaptations for which a person trains. More on this below.

Recovery: what is proven

The Cochrane systematic review (Bleakley and co-authors, 2012) analysed studies of cold water immersion after exercise. The authors concluded that a cold bath probably reduces delayed-onset muscle soreness in the first days after training compared with passive rest. However, the quality of the evidence was low, and data on side effects were lacking.

The meta-analysis by Machado and co-authors (2016) tried to determine the optimal parameters. The best results for reducing pain were observed at a water temperature of about 11–15 °C and a duration of 11–15 minutes. Colder water gave no additional benefit.

For whole-body cryotherapy the picture is weaker. The Cochrane review (Costello and co-authors, 2015) found insufficient evidence to confirm or refute its effectiveness for muscle soreness and recovery. The FDA, in a 2016 consumer warning, also noted the absence of evidence of its medical benefit and pointed to the risks.

So the most honest formulation is this: a cold bath moderately reduces subjective pain and the feeling of fatigue in the following days. This is useful when you need to quickly ‘pull yourself together’ between events, but it is not the same as accelerated recovery of muscle structures.

The flip side: cold and hypertrophy

The most important study for gym-goers was carried out by Roberts and co-authors (2015). Young men performed strength training twice a week for 12 weeks; after each session one group sat in cold water, the other did light active recovery on a stationary bike. In the cold-bath group the gain in muscle mass and strength was smaller.

In the same work the acute part showed that a cold bath after training weakened the activation of anabolic signalling pathways and satellite cells in the muscle over the following hours and days. A similar result was obtained by Fyfe and co-authors (2019): cold water after strength training inhibited the hypertrophy of muscle fibres, although the gain in strength in their study did not suffer substantially.

The logic is simple: inflammation and other ‘stress signals’ after training are not only a problem but also part of the mechanism of adaptation. By suppressing them, we reduce pain, but we may also reduce the stimulus for growth.

For endurance training the data are ambiguous: some studies find no harm to aerobic adaptations, and some even describe positive changes. However, these data are less consistent than the results on hypertrophy.

The practical takeaway: if your goal is building muscle mass, you should not regularly take a cold bath immediately after strength training. But if you need to recover between events at a tournament, the short-term benefit may outweigh it.

Safety and practical parameters

The review by Tipton and co-authors (2017) entitled ‘Cold water: kills or cures?’ reminds us that immersion in cold water is a physiologically powerful stress. Cold shock raises the heart rate and blood pressure, and in people with heart disease can provoke an arrhythmia.

• Water temperature — about 11–15 °C; colder gives no obvious advantage but increases the risks.
• Duration — 10–15 minutes; on first experience — less.
• Enter gradually, control your breathing in the first seconds.
• Never do the procedure alone, especially in open bodies of water.
• After the bath — warming up with dry clothes and a warm drink, without sudden overheating.

Contraindications are usually considered to be cardiovascular disease, uncontrolled hypertension, Raynaud’s syndrome, cold urticaria, cryoglobulinemia, open wounds, as well as pregnancy. In the case of any chronic diseases the decision should be made together with a doctor.

Cryochambers have their own risks. Cases of skin frostbite have been described, especially with wet skin or violation of the procedure rules, and in nitrogen-vapour chambers there is a risk of suffocation due to the displacement of oxygen. The procedure must take place in a certified facility with staff present.

Editorial conclusions

Cold baths moderately reduce muscle pain and the feeling of fatigue in the following days after a load. For whole-body cryotherapy there is as yet no convincing evidence of benefit.

Regular immersion in cold water immediately after strength training can hinder muscle growth, so during a mass-building period it is better to refrain from it or to shift the procedure in time.

Cold is most appropriate in a tight competition schedule, when well-being ‘here and now’ matters, and the safe parameters are 11–15 °C and 10–15 minutes.

The editorial team also recommends reading our materials on the sauna after training, on active recovery and on massage for recovery.

References

1. Roberts LA, Raastad T, Markworth JF, et al. Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. J Physiol. 2015;593(18):4285–4301.
2. Bleakley C, McDonough S, Gardner E, et al. Cold-water immersion (cryotherapy) for preventing and treating muscle soreness after exercise. Cochrane Database Syst Rev. 2012;(2):CD008262.
3. Costello JT, Baker PR, Minett GM, et al. Whole-body cryotherapy (extreme cold air exposure) for preventing and treating muscle soreness after exercise in adults. Cochrane Database Syst Rev. 2015;(9):CD010789.
4. Machado AF, Ferreira PH, Micheletti JK, et al. Can water temperature and immersion time influence the effect of cold water immersion on muscle soreness? A systematic review and meta-analysis. Sports Med. 2016;46(4):503–514.
5. Fyfe JJ, Broatch JR, Trewin AJ, et al. Cold water immersion attenuates anabolic signaling and skeletal muscle fiber hypertrophy, but not strength gain, following whole-body resistance training. J Appl Physiol. 2019;127(5):1403–1418.
6. Tipton MJ, Collier N, Massey H, Corbett J, Harper M. Cold water immersion: kill or cure? Exp Physiol. 2017;102(11):1335–1355.
7. U.S. Food and Drug Administration. Whole body cryotherapy (WBC): a "cool" trend that lacks evidence, poses risks. Consumer Update; 2016.