Cryotherapy aka “icing” – Is it really effective?

Cryotherapy is a therapeutic technique utilizing the application of a cooling device to the site of injury. Cryotherapy is essentially another way of saying you are “icing” an injury.  Most people have heard about the “R.I.C.E.” method: Rest-Ice-Compression-Elevation, but is it truly an effective technique for promoting healing? The answer to this question is complicated and depends on what exactly is meant by “healing”.  Recent research and systematic reviews are questioning the effectiveness of the icing method and calling for caution or reevaluation regarding cold therapy. Below, I will describe the effects icing has on various physiological processes and explain what the current views in research are. Sources are cited at the bottom for further reading on the topic.

Metabolic effects: Localized icing decreases tissue metabolism, which decreases the need for oxygen. The potential benefit to this is the reduction of what is called a “secondary hypoxic injury”, which is an indirect form of damage to the cells around the actual injury due to an imbalance in oxygen delivery versus oxygen need. Ice is thought to slow the need for oxygen and reduce the deficit, which ultimately results in a reduction of damage to surrounding tissues. This is only beneficial when ice is applied immediately after injury.

Circulatory effects: Cold therapy induces vasoconstriction of vessels, which means they get narrower, which results in a decrease in blood flow to the area. Icing can also reduce membrane permeability. Both can be helpful in the prevention or reduction of secondary hypoxic injury as described above. Many cold therapy products promote reducing swelling, edema and hemorrhaging. The current research does not support icing have an affect on hemorrhage or reducing edema, but it can help to prevent edema if applied immediately (within a minute) of injury. The ice must be applied before any edema has formed. Once there is edema and subsequent swelling, it is too late, and applying ice will have no effect on edema or swelling. They key here is that it can prevent edema, but it can’t do anything once the edema has occurred so rapid application is necessary.

Inflammation Effects: Acute inflammation is actually a good thing that occurs after an injury. The inflammatory response is essentially your healing response and it is only maladaptive if prolonged beyond the normal healing time. In terms of cryotherapy, more research is warranted on the effects of ice on inflammation. Most research has focused on induced inflammation or the healing of surgical wounds and the results are conflicting. Research seems to support that icing may delay the overall inflammatory response, but does not alter it in the end. The inflammatory process is necessary for healing to occur so there may be some concerns about applying ice if it delays this vital healing response.

Pain Effects: Both A and C fibers are sensitive to temperature changes, and cooling them reduces their conduction velocity, which eventually results in the numbing sensation of the skin. The colder it is, the more the effect of pain reduction. Ice can be an effective method for reducing pain if the cold is well tolerated by the patient. Care must be taken to not apply ice directly over superficial (close to the skin) nerves because very prolonged icing can induce nerve damage.

Sensory and Motor nerves: Similar to above, cooling decreases the velocity of sensory and motor nerve conduction. Sensory nerves are our nerves that conduct information about sensation such as touch and where our body is positioned in space to the brain for processing. Motor nerves are our output for movement, such as contracting muscles to perform some action. At 10 degrees Celsius (referring to nerve temperature not skin temperature), nerve conduction is blocked in many, but not all nerves. The effect on the sensory and motor nerves can alter proprioception and muscle force production respectively, so there is a great concern with icing a player and then sending them right back into the field to keep playing when nerve conduction in the injured area has been reduced.

What about ice baths and full body immersion?

Ice baths should generally be avoided. The main benefit to an ice bath would be to prevent hyperthermia in situations that require immediate cooling of the tissues to save a life. Full body immersion in ice baths has the following effects and all are negative: increases heart rate, blood pressure, oxidation, cortisol and free radicals. Decreases antioxidants and cerebral blood flow (flow of blood to the brain), which can be very dangerous. Some see benefit in the camaraderie of engaging in ice baths for team bonding drills, but one could argue there are better, less damaging ways to do this.

Take home message about cryotherapy:

Cryotherapy can be effective at reducing pain and secondary hypoxic injury as well as preventing (but not reducing) edema and swelling. However, we need to consider whether the benefits outweigh the negatives and whether there is something better we can be doing to promote healing. Research seems to support compression and elevation over icing so we may need to change the “R.I.C.E.” method to the “R.C.E.” method. Icing can be effective at reducing edema only when applied prior to the formation of the edema, but there is little sense in applying ice long after an injury has occurred unless the tissues require cooling for some alternative reason.

Other things to consider:

1. Applying ice directly over a superficial nerve for a very long time can cause damage to the nerve so do not apply ice for an extended period (such as many hours or a whole day).
2. Wet crushed ice works better than “dry” cubed ice – the ice should be touching all surfaces so the smaller the ice pieces, the better the effect will be.
3. The cooler you can get the tissues, the better the effect will be of reducing secondary hypoxic injury so icing for at least 30 minutes in one sitting is necessary for this effect to take place, but keep in mind the duration will vary depending on the location of the injury, the amount of adipose tissue on the individual etc.

Sources:

Bleakley, C. (2004). The Use of Ice in the Treatment of Acute Soft-Tissue Injury: A Systematic Review of Randomized Controlled Trials. American Journal of Sports Medicine, 32(1), 251–261. doi:10.1177/0363546503260757

Bleakley C, McDonough S, Gardner E, Baxter GD, Hopkins JT, Davison GW. (2012, February 15). Cold-water immersion for preventing and treating muscle soreness after exercise. John Wiley and Sons, Ltd. for The Cochrane Collaboration for Systematic Review.

Costello, J. T., & Donnelly, A. E. (2010). Cryotherapy and joint position sense in healthy participants: a systematic review. Journal of Athletic Training, 45(3), 306–316. doi:10.4085/1062-6050-45.3.306

Guilhem, G., Hug, F., Couturier, A., Regnault, S., Bournat, L., Filliard, J.-R., & Dorel, S. (2013). Effects of air-pulsed cryotherapy on neuromuscular recovery subsequent to exercise-induced muscle damage. The American Journal of Sports Medicine, 41(8), 1942–51. doi:10.1177/0363546513490648

Guilhem, G., Hug, F., Couturier, A., Regnault, S., Bournat, L., Filliard, J.-R., & Dorel, S. (2013). Effects of air-pulsed cryotherapy on neuromuscular recovery subsequent to exercise-induced muscle damage. The American Journal of Sports Medicine, 41(8), 1942–1951. doi:10.1177/0363546513490648

Knight, K., & Draper, D. (2012). Therapeutic Modalities: The Art and Science [Hardcover] (p. 528). LWW; Second edition.