Cryotherapy – Ice for Healing Running Injuries
Icing is a core part of my recovery process and I've consistently found it to dramatically improve muscle healing. Short periods of ice (~20 minutes) will reduce blood flow which may limit further damage due to excessive inflammation. Longer periods (several hours) of icing increases blood flow, which improves healing. It's vital to use ice (frozen water), not a gel pack to prevent skin damage and for effectiveness.
- 1 Cold Induced Vasodilatation
- 2 The (Lack) of Science
- 3 Common Recommendations
- 4 Longer Applications
- 5 My Approach
- 6 Frostbite and skin damage
- 7 The Danger of Gel Packs, Ice Blocks, and Frozen Vegetables
- 8 Monitoring Skin Temperature
- 9 Typical Skin Temperatures
- 10 Ice, Inflammation and Healing
- 11 Ice and DOMS
- 12 See Also
- 13 References
1 Cold Induced Vasodilatation
Cold initially reduces blood flow, but after about 20 minutes the body increases blood flow, possibly to prevent skin damage. This is called Cold Induced Vasodilatation (CIVD) and has been known about since 1930). It's important to stay warm overall while icing a muscle, as reduced body temperature prevents CIVD. This alternating reduction in inflammation and increased blood flow is believed to act as a 'pump', speeding up heeling. This cycle typically takes a few minutes, as shown below.
2 The (Lack) of Science
There is remarkably little science produced on Cold Induced Vasodilation. A 2004 analysis of the available research at the time stated "Currently, no authors have assessed the efficacy of ice in the treatment of muscle contusions or strains. Considering that most injuries are muscle strains and contusions, this is a large void in the literature." A 2008 study stated in its conclusion "There is insufficient evidence to suggest that cryotherapy improves clinical outcome in the management of soft tissue injuries". We'll therefore look at some anecdotal, real world experiences and recommendations.
3 Common Recommendations
The general recommendation for ice is to apply it for 20 minutes, then remove it for 20-60 minutes, repeating this cycle several times. The general advice is to avoid applying ice for too long as it can damage the skin. I have found while this approach does help a little, it is not as effective as leaving the ice in place for a much longer period.
4 Longer Applications
Does a longer period make sense? Well, a Study has shown that the time needed to cool a muscle varies with the thickness of the fat surrounding the muscle. To lower the temperature 1 cm into the muscle by 7 degrees C, it takes ~8 minutes of ice for 0-10mm fat, but ~60 mins for 21-30mm fat. This suggests that a simplistic 'apply for 20 minutes' guide is inappropriate; to impact tissue that is an inch deep would require at least an hour. One study applied ice for 30 minutes and recorded the temperature at 1 and 2 cm into the muscle (below the fat layer). The results indicated that the minimum temperature was not reached during the application, but 6 to 9 minutes after the application finished. This suggests that 30 minutes was not sufficient to fully cool the muscle. Other factors to consider:
- Any barrier between the bag of ice and the skin will require a longer time period.
- Massaging with ice requires less time to cool the muscle than passive application, but it does not result in a lower temperature.
- Compression also reduces the time required to cool the muscle.
5 My Approach
My personal approach is to apply ice for much longer; often for hours continuously. I find that this produces much deeper healing and I have never had any problems. However, there are a number of conditions that would make this approach dangerous, such as poor circulation, diabetes or arthritis. You should also be careful about applying ice for prolonged periods at joints such as elbow or ankle; the nerves are closer to the surface. I know some people like to use a compression bandage to hold the ice in place, adding compression to the cooling. Care should be taken after prolonged icing as the cooled muscles will have impaired control.
6 Frostbite and skin damage
Damage to cells occurs around -10c/14f, which is well below the temperature of ice. In fact, the temperature of the skin where it is in contact with an ice pack is normally about 5c/41f. Animal studies that chilled the skin and underlying fat to between -1c/31f and -7c/19f showed no signs of tissue damage.
7 The Danger of Gel Packs, Ice Blocks, and Frozen Vegetables
I use ice cubes in a hefty Ziploc bag rather than gel packs as Gel packs start off too cold, and then warm up too quickly. If you use ice, the temperature will remain constant around freezing until all the ice is melted. You should avoid large blocks of ice, as the ice will be at freezer temperature which is cold enough to damage the skin. The goal is to have a mixture of ice and water, which will be around freezing point. Likewise, frozen vegetables can remain too cold and do not result in a layer of water.
8 Monitoring Skin Temperature
You should monitor your skin temperature closely, and if it gets too cold you should stop. Generally, I find my skin temperature doesn't drop below 2c/35.6f and is typically warmer than that. I've used several different technologies for skin temperature monitoring, each with their own advantages.
- A thermocouple is a temperature sensor on the end of a wire, which allows you to continuously monitor your skin temperature, and I have one that supports four sensors at the same time and is only $31.98 USD at Amazon.com. This is probably the most cost effective approach.
- A Thermal Camera is great as it allows you to see not only the temperature at one spot, but the pattern of temperature changes. The downsides are that you have to take the ice off to check the temperature, and the cameras are expensive. I'd use this with the above temperature sensor rather than instead of it. I recommend the FLIR ONE $398.00 USD at Amazon.com, but check out Thermal Camera for more details.
9 Typical Skin Temperatures
I've made a number of tests, monitoring my skin temperature for up to three hours. The graph below shows three tests where I took temperature readings every 15 minutes, and it's fairly typical of what I see. The skin temperature initially drops fairly quickly, dropping to around 5-15c/40-60f within five minutes, and stabilizing around 5-10c/40-50f within 15-20 minutes. After that, the temperature tends to be reasonably stable, and most of the variation is down to how much the ice water is moved. If the bag of ice water is kept very still, the skin temperature will rise somewhat, but if it's actively agitated, then the skin temperature can drop. It takes some effort for me to get the skin temperature below 2c/36f, and obviously, the skin temperature never drops below freezing, as the ice water isn't that cold.
Here are some other tests I performed, showing some of the variation you might experience, with temperatures rising and falling.
10 Ice, Inflammation and Healing
A 2010 study has shown that inflammation is necessary for healing, something that has been known for some time. The study did not look at the use of ice for healing, only the role of inflammation itself, though it's conclusions were widely misinterpreted.
11 Ice and DOMS
12 See Also
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- C. O'Brien, Reproducibility of the cold-induced vasodilation response in the human finger., J Appl Physiol (1985), volume 98, issue 4, pages 1334-40, Apr 2005, doi 10.1152/japplphysiol.00859.2004, PMID 15579576
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- Putting ice on injuries could slow healing http://www.telegraph.co.uk/health/healthnews/8087777/Putting-ice-on-injuries-could-slow-healing.html
- Ching-Yu Tseng, Jo-Ping Lee, Yung-Shen Tsai, Shin-Da Lee, Chung-Lan Kao, Te-Chih Liu, Cheng-Shou Lai, M. Brennan Harris, Chia-Hua Kuo, Topical Cooling (Icing) Delays Recovery from Eccentric Exercise-Induced Muscle Damage, Journal of Strength and Conditioning Research, 2012, pages 1, ISSN 1064-8011, doi 10.1519/JSC.0b013e318267a22c