We put up a couple of links to some health-related articles on our Facebook page yesterday. Rob Leduc provided some excellent comments on those links. For the effort that went into those comments, they seemed worthy of their own blog post. So here are the article links accompanied by Rob’s take on them.
First up was this article on the possibility of chiropractic treatments increasing speed in runners:
Can Chiropractic Improve Running Speed?
Rob’s comment: By trade, I’m a clinical trials statistician. While I’m not a medical professional of any kind, nor do I have experience in chiropractic studies, I do have a lot of experience in general methodology and the interpretation of studies.
First, I want to say that this study is particularly well written. It is very easy to gather from the article what the authors were trying to do and how they went about it. The authors are clear that this is a pilot study to see if it is worth doing a larger study, but not likely to establish good evidence for the treatment due to the small numbers of participants relative to the amount of variability in the variables to be measured. Their practices in conducting the study as described are first rate.
Secondly, this study is of healthy runners, and relatively good ones (1500m in just over 4 min). It is not about treatment for injury. The question under study is whether manual chiropractic treatments designed to improve hip extension performed on healthy participants will result in greater running velocity; in particular, velocity measured over 30m when the participants are already moving at top speed (they had 30m to accelerate first before the 30m that were measured). So this study won’t say whether chiropractic treatment to rehabilitate injury or dysfunction is useful or not – it’s not the point of this study.
Third, the effect measured by the study is not that large unless you’re a pretty competitive runner already. Here I may be disagreeing with the authors, in spite of their Cohen’s d-statistic. A larger study may produce a different result, but we have some idea of efficacy from this pilot study. On average, the treatment group in the study improved their times over 30m at top speed by 0.06 seconds, which was not significantly different from the control group who did not receive therapy. However, if that change held constant over a 5K, we’re talking about a 10 second improvement. At best, based on the .135 second decrease at the edge of the confidence interval, we’re talking 22 or 23 seconds; a bigger effect, but an optimistic projection. These changes would be of interest to someone running sub-20 5K’s, but not for the average running boom duffer. Additionally, we actually don’t know that we can extrapolate to 5Ks like this; the actual measurement was of sprinting 30m and the effect on distance running was not measured by the study.
Finally, the authors do point out that there may be risks to such a treatment. In the introduction, they state that chiropractic treatment of asymptomatic individuals is not considered appropriate or justified by evidence, although many athletes seek such treatment. They also point out there can be too much of a good thing – too many of these treatments in a short time period may be risky. For this reason, in their inclusion/exclusion criteria for the study, they do not allow any participant to enroll if they have had such manual therapy. It would take a larger study and possibly longer term follow-up over repeated treatments to identify these kinds of problems.
I am confident from this article that the researchers are capable, but what they have shown so far is that their treatment increases the range of motion in the hip. The difference in change in 30m velocity between the two groups was consistent with chance variation, i.e. was not statistically significant, and larger studies are required to give concrete evidence of even this level of benefit.
Next was the much talked about WSJ article on how too much running could kill you:
One Running Shoe In The Grave
Rob’s comment: I’ve read this in the popular press, but haven’t seen any of the real research. The WSJ is not a good source for scientific information. They have a well established agenda against requiring randomized trials for health claims, for example.
I’ve checked Heart online, and it doesn’t appear that the editorial is available yet; even if WSJ has an advance copy, they don’t give a reference to what the “other study” is. But I’m highly suspect of the results as reported – it smells a lot like cherry picking of the data.
It’s possible that there can be too much of a good thing, but I doubt they have the numbers of participants at a high enough ability to make these kinds of claims; even if they did, association is not causation.
And let everyone be assured, I am no elite marathoner with an axe to grind here.
Lastly, there was an article that came out as a response to the WSJ piece:
The Too-Much-Running Myth Rises Again
Rob’s comment: I’ll be interested to see the Heart editorial next month and look up the other studies it refers to. At best at this point in the research there is a statistical association, but association is not causation. Additionally, these associations can be spurious, subject to confounding variables and biases caused by the method of selection of study participants. It’s a very tricky business.
We love it when members of the Legion get involved in what we do, keep it up!