That is what the barefoot running community and the anti-running shoe community would have you believe. You see this claim being made all the time on barefoot running websites, books and on running forums. We know that the barefoot running community are really good at all sorts of intellectual dishonesty, should we believe them on this one as well?
Given the strength of the claims being made, you would expect there would be at least some evidence to back it up wouldn’t you?, but there is none! They only want to believe it to be the case as it helps their agenda. Certainly many individuals who start barefoot running claim that their foot and leg muscles are stronger – but are they really stronger? Or do they just feel different as the barefoot running gait is different? Or do they deceptively feel stronger because they want them to feel stronger? (see this post on why individual experiences are flawed).
In the context of the lack of evidence either way as to if running shoes weaken muscles or not, what other information do we have that could guide us to some sort of rational conclusion rather than some uniformed nonsense due to the wearing of blinkers. What about foot orthotics? Do they weaken the foot? You certainly see it claimed a lot by those who have not read the evidence. Two studies have looked at muscle strength and the use of foot orthotics. One by Mayer et al actually showed the opposite and foot orthotics increased muscle strength! The other study that looked at this showed after 4 weeks of orthotic use that there was a non-statistically significant increase in strength, so certainly no signs of a decrease in muscle strength which I would have thought would start to show by 4 weeks if it was going to happen. Now, obviously foot orthotics are not running shoes, but despite widespread claims that foot orthotics decrease muscle strength, all the research evidence is that either they do not or they increase strength!. Can this be extrapolated to running shoes? Maybe? Maybe not? What this research does do is calls into question the unsupported claims that running shoes do weaken the muscles.
Then there is the one EMG (electromyography) study that compared running shoes to barefoot. They found no systematic differences between barefoot or running shoes. Some muscles activated earlier in barefoot and some activated earlier in the running shoe. If the running shoes were weakening muscles, then why are the EMG studies NOT showing a systematic decreases in timing and amplitude of muscle activation? Certainly no sign of any muscle weakening here!
What about the Bruggeman et al study that looked at muscle strength after runners were randomised to their conventional shoe vs the Nike Free (which is not really barefoot, but is a minimalist shoe). They showed what appeared to be an increase in muscle strength in the Nike Free group. I have no problems with the study (except a few minor issues and it was funded by Nike). But consider these two points:
- The study was NOTHING to do with conventional running shoes weakening foot and leg muscles (which strangely has been interpreted as showing that by some!).
- Why did the Nike Free group of runners get an increase in leg muscle strength? Was it because being close to running barefoot is a good thing? (this is the interpretation that the barefoot running community would like to put on it). But what about the opposite conclusion? Could it be that the muscles got stronger because they had to work harder in the Nike Free shoe? Increased muscle activity is a bad thing as it is a sign of an inefficient gait. If the muscles are having to work harder, then performance will be affected. Surely that is a bad thing? Strange how the barefooted community with blinkers on can draw one conclusion when there are other possible conclusions that can be drawn.
Conclusion: We actually have no idea if running shoes lead to weaker muscles or not. However, if we want to extrapolate the orthotics and the EMG evidence, then it could certainly be suggested that they do not. There is certainly more information pointing to running shoes not weakening muscles than the nonsenscial and unsupported claims by the barefoot running community.