Yesterday as I was icing my plantar fasciitis-stricken heel for what feels like the millionth time, I began wondering what sorts of sports recovery technologies on the horizon might help get me past this despised duty. A recovery technology that has been getting a lot of celebrity and athlete press lately is cryotherapy, or ultra low temperature therapy. Not for just freezing off warts, local and whole body cryotherapy is now proposed to be useful for muscle pain, muscle metabolism, performance, depression, anxiety, and acute and chronic inflammation, among other things.
Ice bath vs cryotherapy! Image from OhioCryo
Like many “health” trends today, there is little evidence that cryotherapy is effective. I’m not saying it’s ineffective – my skeptical scientist perspective just recommends that you should not rush to go shell out $90 to stand in a cryo chamber for 3 minutes - which is the rate at Kryolife in NYC. Does that sound ridiculous? Well there’s more: they recommend 10-20 treatments. The misleading stacked bar graph in their brochure (below) implies cryotherapy patrons should expect reductions in pain, but further examination shows that the graph is only showing a self reported pain scale from 9 patients with Bechterew disease (a chronic inflammatory disease). A more explicit graph would show:
I found a pretty interesting scientific review of whole body cryotherapy (WBC) that examined evidence from 10 different controlled trials to determine the efficacy and effectiveness of WBC. While some of the studies were limited and not entirely conclusive, only one of the studies showed WBC helpful in rehab – adhesive capsulitis of the shoulder rehab.
To me, the most interesting figure in this journal article is the performance indicators graph. While reported pain is subjective and very much mental, measurement of quantitative performance is absolute. This forest plot summarizes different performance metrics of people who underwent WBC and people who did not. The outcome effect ratio is demarcated with the green line, while the vertical black line shows the interval or range of outcomes, with 95% confidence. Forest plots may look complicated, but they're actually pretty easy: think of the horizontal line as the representation of the test group. If the horizontal line touches the vertical line, the results aren’t significant. Why? Because this group falls within both the left AND the right side of the outcome effect ( with 95% probability). That means a subject in the group could be on the left - benefits from WBC - OR on the right: benefits from nothing. We can't reach a conclusion. However, if the horizontal line is completely in a camp, we have a 95% probability of knowing one of the treatments indeed changes the outcome. We see from this figure that one of the performance indicators actually was completely on the left side: Tennis shot accuracy is improved with whole body cryotherapy!
- Number of patients (it’s not clear only 9 patients were tested)
- What type of patients were tested, ideally from a broader subset (because Bechterew disease is a pretty specific population)
- Comparison against a control group – because the placebo effect is often quite significant.
- A different data visualization – stacking bars on top of one another is purposefully deluding
I found a pretty interesting scientific review of whole body cryotherapy (WBC) that examined evidence from 10 different controlled trials to determine the efficacy and effectiveness of WBC. While some of the studies were limited and not entirely conclusive, only one of the studies showed WBC helpful in rehab – adhesive capsulitis of the shoulder rehab.
To me, the most interesting figure in this journal article is the performance indicators graph. While reported pain is subjective and very much mental, measurement of quantitative performance is absolute. This forest plot summarizes different performance metrics of people who underwent WBC and people who did not. The outcome effect ratio is demarcated with the green line, while the vertical black line shows the interval or range of outcomes, with 95% confidence. Forest plots may look complicated, but they're actually pretty easy: think of the horizontal line as the representation of the test group. If the horizontal line touches the vertical line, the results aren’t significant. Why? Because this group falls within both the left AND the right side of the outcome effect ( with 95% probability). That means a subject in the group could be on the left - benefits from WBC - OR on the right: benefits from nothing. We can't reach a conclusion. However, if the horizontal line is completely in a camp, we have a 95% probability of knowing one of the treatments indeed changes the outcome. We see from this figure that one of the performance indicators actually was completely on the left side: Tennis shot accuracy is improved with whole body cryotherapy!
Forest Plot of Performance Outcomes
So it’s not a lost cause, WBC could be beneficial, but remember these studies just compare WBC to control treatment, which is active recovery but no cold therapy. There are several other ways to cool the body, including ice packs and water baths. While cryotherapy is certainly the coldest method– at about - 250 degrees Fahrenheit it’s the coldest temperature in the world – that doesn’t mean it transfers cold to the body the most effectively. The poor thermal conductivity of air means that despite establishing the largest temperature gradient, the ability to lower the subcutaneous and core temperature of the body is relatively weak. This makes sense – being in 40 degree water will get your teeth chattering a lot quicker than 40 degree air. So although WBC benefits from holistic cooling, it looks like crushed ice (which benefits from phase transfer) and ice baths can get the body just as cold - or even colder.
So, I guess I’ll begrudgingly go grab a frozen water bottle for my heel; no cryotherapy for me.
So, I guess I’ll begrudgingly go grab a frozen water bottle for my heel; no cryotherapy for me.
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