I going to start off with this image¹:
There is plenty of the usual propaganda and rhetoric about foot orthotics weakening muscles in the crankosphere blogosphere, therefore they are evil: Truth or lie?
I already addressed the issue of running shoes weakening muscles (they don’t); but that has not stopped the fan boys still claiming that they do. What about foot orthotics? What does the actual evidence or research say?
Firstly, here is a study that one of my Honours student, Mitch Daoud did a couple of years ago that we won’t be submitting for publication for a reason I will come back to. We recruited three groups of runners: a running shoe wearing group; a running shoe and foot orthotic wearing group; and a barefoot/minimalist group. A number of muscle strength tests were done on them: hallux and lessor toe plantarflexion strength, ankle inversion and dorsiflexion strength using several trials of a hand held dynamometer; and calf muscle endurance (using a validated measure of heel raises in time with a metronome). With the exception of the last measure, all were normalized to body weight.
Mitch was blinded as to which group the runner was in when doing the muscle strength testing to avoid the potential for any preconceived biases. Here are the results:
As you can see, the foot orthotic group was the strongest in almost all of the parameters. That surprised even me and was not what we were expecting. The minimalist group does appear to be stronger than the shod group. Even more surprising was the foot orthotic group scored the highest in the calf muscle endurance. I would have thought that the barefoot/minimalist group would have been higher, when it was the lowest! Not the remotest hint of foot orthotics weakening muscles.
Now for the problem and why we are not going to try and publish the data. There were only 4 subjects in the minimalist/barefoot group (and it can’t escape our attention that a lot of fan boys have no problems with a group size of 4 when they see a study they like!). As hard as we tried, we just could not recruit any more in the time frame that is an undergraduate project. Simply, there are just not that many people doing the barefoot/minimalist thing out in the real world compared to their high visibility in social media (minimalist shoe sales have now fallen to around only 3-5% of the running shoe market). The numbers are just not there and I guess we were mislead into believing we could find more due to the prominence of it in social media.
Having said that, the data is worth putting out there in this blog post for people to make of it what they will. It is pretty clear that even though there is only 4 in the minimalist/barefoot group, the orthotic group is stronger, so there are clearly not the remotest hint of a trend towards the foot orthotic group being weaker and the barefoot/minimalsiut group being stronger as the rhetoric and propaganda from the fan boys would have us believe.
Secondly, the data above is also consistent with ALL the other studies on foot orthotics and muscle strength. I just do not get why the fan boys choose to actually ignore what the evidence actually says and just plain make things up when they make their public pronouncements. This is not new evidence; its been around for a while now:
- Mayer et al (2007) showed an increase in calf muscle strength in the orthotic wearing group. The increase in calf muscle strength in the orthotic wearing group is consistent with the data in our study above; though I am unclear on an actual mechanism.
- Jung et al (2011) showed an increase in intrinsic muscle strength in the foot orthotic wearing group
- Our other study (2005) showed no weakness after 4 weeks of foot orthotic use (there was actually a statistically non-significant increase in strength)
These are not cherry picked studies. It is them all. I will update this post the minute any new research on this topic is available, whatever its results. Why do those espousing the rhetoric and propaganda choose to ignore the evidence (hence the image at the top of the post)? Even worse, why do they continue o do it even after the above research is pointed out to them?
As always, I go where the evidence takes me until convinced otherwise, … and I am a slave to the data: Truth or lie? … you be the judge.
1. Thanks to Robert Issacs for sharing the image!