Published on April 16th, 2014 | by Tils2
To Ice or Not To Ice?
Back in late 2013, I became aware of a blog post which had gone viral, and which was being linked by friends of mine in both the derby world and the horse world. It related to icing injuries, and it fairly plausibly seemed to say icing was a bad thing. This post has recently surfaced again and is doing the rounds in the derby community. My original response to this was to read it again, to apply some scientific rigour to what was being said, and do my own research.
The blog was pretty clear that we ice to reduce swelling, and that we shouldn’t because inflammation is a crucial part of the healing process when it comes to muscle damage.
That last part is true–muscle repair is basically controlled by an immune response. But do we really ice to reduce swelling? I know that’s not why I ice! I ice because the structures which are the most difficult to heal–the tendons and ligaments–are also the most susceptible to cell death. Increasing the temperature above 45C has been shown to cause much higher rates of cell death in tendon cells of horses, for example. A University of Bristol study showed that equine tendons can heat up to 45C during exercise, but at 48C, they show approximately 80% of the tendon cells die.
Why should we care about that? Consider this – horses are designed to be able to run for prolonged periods in order to escape from predators. There is absolutely no reason to think human tendon cells are any different in terms of how heat will damage them, and our tendons are not nearly so close to the surface as those of a horse, therefore any innate cooling ability will be proportionally worse.
Well, by icing, you lower the temperature of cells, and this slows their metabolic rate, which means their requirement for oxygen is lower. So if the blood vessels are damaged at the site of the injury (bruising), oxygen transport is impaired. You can then get cell death through lack of oxygen, which is made worse by heat at the site since this increases the metabolic rate of the cells. So, when you ice, you lower the cells’ metabolic rate, which means they are less likely to die from lack of oxygen. Especially important in structures which are difficult to heal, such as tendons and ligaments, which have a very poor blood supply to start with.
So maybe icing after injury isn’t such a bad thing after all. However, a subsequent article on the site the original viral post came from points out that you can get cell death after icing, so shouldn’t we be concerned about that? The link which is mentioned (but not properly cited – it’s here if you’re that interested) is presented as evidence that even after you’ve stopped icing, blood vessels may still be constricted and therefore blood flow impeded, which can lead to cell death.
What the blog doesn’t mention is that the study was undertaken on cryotherapy devices. These are specifically designed to provide prolonged cooling–for example the DonJoy machine can cool for 7 hours, and the PolarCare for 8-11 hours. All the devices are prescription-only class II medical devices in the USA. Sure, you can buy them on eBay: but you shouldn’t! They are designed for use post-operatively, under the supervision of a medical practitioner. What the abstract of the paper doesn’t tell you is how long the machines were used for to gain these results. Assuming they were studying the recommended protocols (here’s the instructions for one of these devices) which include continuous use on the first day after surgery, and which all include use for an hour–then I think it’s safe to say the results bear little relevance to our situation.
Athletes icing an injury should follow this protocol:
- Never ice for longer than 20 minutes.
- Icing is most effective if done for 15-20 minutes.
- Always leave at least 45 minutes between icing sessions – the skin should be warm and have normal sensation before you start icing again.
- Always have something between your skin and the ice (a teatowel, j-cloth, brown paper, whatever, doesn’t much matter).
I’d give you my opinion on how the mouse study fits in to all of this–but the poor citation means despite searching the abstracts of the journal mentioned, I can’t find the original paper.
I’m totally open to the idea that icing may not be the best thing to do for an injury. What I’m not convinced about is that the series of articles on Athletic Medicine give us credible, scientific evidence that icing is bad and we should stop it.