Is There Really A New Exercise Which Will Cure Plantar Fasciitis?
This study showed no benefit at 1 month, 6 months and one year. There was only a benefit noted at the 3 month datapoint, which then disappeared.
Highly touted High-Load Strength Training Shows No Benefit In Long Term
Last fall, you may have read in the New York Times that an article had been published in the Scandinavian Journal of Medicine & Science in Sport (August 2014) discussing the benefit of high load strength training for plantar fasciitis. The NY Times then described the wonders of this “one simple exercise” in alleviating the pain of plantar fasciitis. The implication was that this particular exercise was the only thing that was going to work. The exercise is done while standing on one foot on a box with the toes dorsiflexed on a rolled up towel. Although if you use a section of the New York Times rather than using the entire paper for your bird cage that may have equivalent effects.
If you take enough data points you might very well be able to prove anything. You may even believe what you see with that limited subset of data. (See the body of work saying there is no human contribution to climate change using limited data sets and cherry picked sources.)
How Large, Precise and Lasting Was the Treatment Effect?
This question is a basic question asked in the American Medical Association’s Guide to the Medical Literature, subtitled “A Manual for Evidence-Based Clinical Practice”. We don’t find the component parts of this question impressively demonstrated in this study.
The main problem is that the article (Rathleff 2014) found a significant improvement ONLY at 3 months (between the group performing the one leg calf raise and those performing a stretch that I’m not fond of). Both groups used “shoe inserts”. Another problem is that was called the control group was a comparison and not a control group. We’ll continue to use their term.
At 1 month, 6 months and 12 months, there were no significant differences or benefits of this exercise over the control group which just used one stretch and shoe inserts. If we found an exercise (like flossing) that made us feel better only at age 30 and gave us fewer cavities and better gums but only at age 30, there would be no benefit over other exercises that worked equally well for age 20, 40, 50, and 60. There would be no study or media attention given. But with the dearth of truly useful evidence based sports medicine the insignificant gains significance.
Most would like to use a treatment that enables them feel better in 4-6 weeks and at 4 to 6 months. The 3 month data point as a single marker is not useful.
And what is the relevance of this to runners? The study group and control group were both overweight with a BMI averaging 26.4 in the study group and 27.1 in the control. (Less than 25 is considered normal weight. See CDC Healthy Weight – http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/)
There were not many people in this study. Only 24 in the study group and 24 in the control. Using statistical methodology to determine the minimum number to detect a difference in the functional index which they used they required 23 patients in each group. (While the use of “intention to treat” analysis is laudable, can you imagine an approach to cancer treatment being based on a study such as this with only n=24, several dropouts and improvement over a comparative treatment only present at the 3 month mark? Impossible!)
From Ratliff et. al. (2015): “Based on a previous trial, we used a common standard deviation of 18, which showed that 23 patients were needed in each group to detect a statistical difference (power 0.80, alpha 0.05) (DiGiovanni et al., 2003).”
They began the study with 24 in each group. There was a higher drop out number on the study group. Looking at the high-load strength training group there were n=22 measured at 1 month, n=18 at 3 months, n=17 at 6 months and n=18 at 12 months. At the 3 month and beyond time points they were below the levels pre-determined for measuring a detectable difference between groups.
So here we have a study of a few people who were improved in comparison with another control group for “one brief shining moment” which quickly passed. Both groups were ultimately better after 1 year but did not demonstrate a superiority of one treatment over the other. The study design is impeccable. The statistical analysis is elegant. But, the subject number is quite low and the results are clearly open to a different interpretation.
Will this exercise be helpful to some people? Yes it will. Will it be helpful to all and is there a unique benefit demonstrated by this research. No, it is not and there is no unique benefit to this exercise. There is only evidence for a briefly lasting one in this extremely small study which was seen only at the 3 month mark. Not before and not after.
So the hype on this study is just that – media hype with no basis in the evidence contained in the study.
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Digiovanni BF, Nawoczenski DA, Malay DP, Graci PA, Williams TT, Wilding GE, Baumhauer JF. Plantar fascia-specific stretching exercise improves outcomes in patients with chronic plantar fasciitis. A prospective clinical trial with two-year follow-up. J Bone Joint Surg Am 2006: 88: 1775–1781.
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Rathleff MS et. al., “High-load strength training improves outcome in patients with plantar fasciitis: A randomized controlled trial with 12-month follow-up.” Scand J Med Sci Sports. 2015 Jun;25(3):e292-300.
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Running On Empty