Cold Therapies: Cryo 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 flown around all the social networks. However, cold is a double-edged tool: it reduces pain and the sensation of fatigue, but it may weaken adaptations to strength training. The editorial team looked into when cold is appropriate and when it is better to forgo it.

Types of cold therapies

By «cold therapies» in sport, several different methods are meant. The most common and best-studied is cold water immersion (CWI): an athlete sits in a bath or pool with water at a temperature of approximately 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, whose temperature can drop to −110 °C and below. There are also «cryosaunas», in which the head remains outside and the cooling is provided by vapors of liquid nitrogen.

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 their outward similarity, these methods differ substantially in physics. Water removes heat approximately 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 short stay in a cryochamber with air at −110 °C.

How cold affects the body

When immersed in cold water, the vessels of the skin and superficial tissues reflexively constrict, and blood flow in the limbs decreases. The hydrostatic pressure of the water additionally «squeezes» fluid out of the leg tissues toward the central vessels. This is one of the likely reasons for the reduction of swelling after intense exertion.

Cooling reduces the speed of nerve impulse conduction and the sensitivity of pain receptors. This is precisely what explains the rapid analgesic effect of cold and the pleasant sensation 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 the inflammatory and anabolic signaling pathways in the muscle. In the short term this reduces pain and swelling, but in the long term it may interfere with the very adaptations for which a person trains. More on this below.

Recovery: what is proven

A Cochrane systematic review (Bleakley and colleagues, 2012) analyzed studies of cold water immersion after exertion. 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.

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

For whole-body cryotherapy the picture is weaker. A Cochrane review (Costello and colleagues, 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 sensation of fatigue in the coming days. This is useful when you need to quickly «pull yourself together» between starts, but it is not the same thing as accelerated recovery of muscle structures.

The flip side: cold and hypertrophy

The most important study for gym-goers was conducted by Roberts and colleagues (2015). For 12 weeks young men performed strength training twice a week; after each session one group sat in cold water, the other performed light active recovery on a stationary bike. In the cold-bath group the increase 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 signaling pathways and of satellite cells in the muscle over the following hours and days. A similar result was obtained by Fyfe and colleagues (2019): cold water after strength training inhibited the hypertrophy of muscle fibers, although the strength gain in their study did not suffer significantly.

The logic is simple: inflammation and other «stress signals» after training are not only a problem but also part of the adaptation mechanism. 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 regarding hypertrophy.

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

Safety and practical parameters

The review by Tipton and colleagues (2017), titled «Cold water: kills or cures?», reminds that immersion in cold water is a physiologically powerful stress. Cold shock raises heart rate and pressure, and in people with heart diseases it may provoke arrhythmia.

• Water temperature is approximately 11–15 °C; colder gives no obvious advantage but increases the risks.
• Duration is 10–15 minutes; for a 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 abrupt overheating.

Contraindications are usually considered to be cardiovascular diseases, uncontrolled hypertension, Raynaud's syndrome, cold urticaria, cryoglobulinemia, open wounds, and also 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 chambers with nitrogen vapors there is a risk of suffocation due to the displacement of oxygen. The procedure must take place in a certified facility with staff.

Editorial conclusions

Cold baths moderately reduce muscle soreness and the sensation of fatigue in the coming days after exertion. For whole-body cryotherapy there is as yet no convincing evidence of benefit.

Regular immersion in cold water immediately after strength training may inhibit muscle growth, so during a mass-gaining period it is better to forgo it or to shift the procedure in time.

Cold is most appropriate in a tight competitive schedule, when «here and now» well-being matters, and 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.