Do Foot Orthoses Cause Muscle Weakness?

One of the many unsubstantiated claims that barefoot/minimalist running advocates make is the assertion that foot orthotics cause muscle weakness in the feet and legs. A simple review of the medical literature reveals the opposite effect. Researchers have measured that foot orthoses actually cause positive trends in muscle activity during gait.

In their promotion of the benefits of barefoot running, advocates often lump shoes, arch supports and foot orthoses together as a recipe for disaster for the recreational runner. Their argument is the same whether condemning foot orthoses or shoes. Both create muscle weakness and atrophy, while barefoot running will provide the opposite effect. In their oft-quoted paper, Lieberman and colleagues state that “many running shoes have arch supports and stiffened soles that may lead to weaker foot muscles, reducing arch strength.”1 In this article, Lieberman and his co-authors provide no references or data to substantiate this claim.

Consider this statement made by Podiatry Today blogger Nick Campitelli, DPM, regarding the reason people have injuries associated with wearing flip-flops:

“Along the same lines, consider flip-flops. Are flip-flops bad for our feet? Not necessarily. What is bad is functioning in them with weak foot and leg musculature. As a person functions all winter in a supportive shoe, albeit with an arch and/or heel, these muscles weaken or atrophy. An abrupt change to a flip-flop then causes these muscles to become rapidly overused.”2

Not only is there no evidence that supportive shoes cause atrophy of muscles, there is no evidence to validate the preposterous conclusion that these so-called weak or atrophied muscles are more likely to be overused when wearing flip-flops.

Just last week, a barefoot running fan named Kenneth Craig posted a comment on Dr. Campitelli’s blog that states: “Addressing the muscular weakness/ imbalances occurring in the various regions is far more effective in the long term rather than introducing a crutch such as orthoses which could lead to further weakening of the musculature over time.”3

I have previously warned about the need to fact check our bloggers and proponents of new fads in the profession (see http://www.podiatrytoday.com/blogged/who-fact-checking-podiatric-profession ).

The barefoot cult is at the top of the list of those who fail to substantiate their controversial allegations. If barefoot advocates simply took the time to study basic physiology and then read the medical literature, they would realize that their claims about muscle atrophy are without merit.

Any astute clinician or sport scientist knows that the evaluation of muscle function during walking or running is far more complicated than looking for over-activity or under-activity. Either state could be pathologic depending upon the foot type and phase of gait.

Consider the patient with a flatfoot deformity. Murley and others studied electromyography (EMG) muscle activity in 30 adults with flat arched feet and compared them to 30 adults with normal arched feet during walking.4 During the contact phase of gait, the flat arched group demonstrated increased activity of the tibialis anterior and decreased activity of the peroneus longus muscles. During midstance and propulsion, patients with flat arches exhibited increased activity of the tibialis posterior and decreased activity of the peroneus longus in comparison to those patients with normal arched feet. Therefore, a flatfoot posture creates more demand on the foot invertors and has reduced demand on the evertors during gait. Under-activity or over-activity of muscle function can be pathologic and occur in the same patient with a flatfoot deformity.

Of more interest is the follow-up study by the same research team that looked at patients with flat arches and compared the effects of both prefabricated and custom foot orthoses on muscle activity during walking gait.5 Both types of orthoses decreased demand on the tibialis posterior during contact phase while the customized prefabricated orthosis increased the activity of the peroneus longus during midstance. These findings suggest that when patients with flat arches wear foot orthoses, muscle function improves to mirror patterns that occur in feet with normal arches.

Several other studies have demonstrated the increased activity of certain muscle groups of the lower extremity when patients wear foot orthoses.6,7 This body of evidence refutes the myth proposed by the barefoot cult that foot orthoses lead to muscle atrophy and weaken the foot and leg.

I am frustrated by the fact that more of my own patients are questioning the value of foot orthoses based upon reading unfounded allegations on Internet forums. I am quick to advise any patient that there is a wealth of research that contradicts these false assumptions. In addition to their outstanding work on flatfoot and muscle function, Murley and co-workers have published an excellent systematic review of 38 studies of muscle function as affected by footwear, ankle braces and foot orthoses.8 Scrutiny of this wide body of knowledge clearly shows that there is no merit to the false claims made by the barefoot cult regarding muscle function and foot orthoses.

References
1. Lieberman DE, Venkadesan M, Werbel WA, Daoud AI, D'Andrea S, Davis IS, Mang'eni RO, Pitsiladis Y. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature. 2010 28;463(7280):531-5.
2. Available at http://www.podiatrytoday.com/blogged/how-minimalist-shoe-movement-has-af... .
3. Available at http://www.podiatrytoday.com/blogged/defending-my-position-orthoses .
4. Murley GS, Menz HB, Landorf KB. Foot posture influences the electromyographic activity of selected lower limb muscles during gait. J Foot Ankle Res. 2009;2:35.
5. Murley GS, Landorf KB, Menz HB. Do foot orthoses change lower limb muscle activity in flat-arched feet towards a pattern observed in normal-arched feet? Clin Biomech 2010;25(7):728-36.
6. Tomaro J, Burdett RG. The effects of foot orthotics on the EMG activity of selected leg muscles during gait. J Orthop Sports Phys Ther 1993;18(4):532–6.
7. Mundermann A, Wakeling JM, Nigg BM, Humble RN, Stefanyshyn DJ. Foot orthoses affect frequency components of muscle activity in the lower extremity. Gait Posture 2006;23(3):295–302.
8. Murley GS, Landorf KB, Menz HB, Bird AR. Effect of foot posture, foot orthoses and footwear on lower limb muscle activity during walking and running: a systematic review. Gait Posture. 2009;29(2):172-87.



Kevin A. Kirby DPMsays: May 23, 2013 at 11:54 am

Dr. Richie:

Excellent points! Yes, the barefoot and minimalist shoe cult likes to proclaim that foot orthoses and shoes with thicker soles not only weaken the feet but are harmful for people, even though there is no research evidence that supports these claims. Like you suggested, we can no longer sit quietly by and let the barefoot and minimalist shoe advocates continue to belittle what we do as a profession, all to meet their agenda that shoes are the cause of all evils. We all need to become more vocal and publicly directly address the weaknesses of the bizarre ideas that these cultists spread across the internet. Our patients deserve good advice based on science, not unscientific fanaticism that approaches the absurd.

Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine

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Craig Paynesays: May 23, 2013 at 2:15 pm

There are now 4 studies that have looked at foot orthotics and muscle strength. Two have shown in an increase in strength with foot orthotics use, one showed no difference and the 4th showed no differences between the foot orthotic group and non-foot orthotic group.

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cbpaynesays: May 23, 2013 at 2:26 pm

Also, one study has shown running shoes actually strengthen the muscles.

I blogged about that here:
http://www.runresearchjunkie.com/do-running-shoes-weaken-muscles/

Not one study has shown that foot orthotics or running shoes weaken muscles. All the studies done on this topic say the opposite.

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Doug Richie says: May 25, 2013 at 10:22 pm

Thank you Craig for adding additional verification to the message of my blog. Your colleagues at La Trobe University are to be commended for their outstanding contributions to our understanding of foot orthotic treatment effects. My question now: Where are all the barefoot fans and why do you not have any comment on my blog?

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Footman123says: May 23, 2013 at 4:56 pm

If you already have an overpronated foot to begin with, the worst thing to do is jog and walk barefoot because such an overpronated foot is pronating from late midstance to propulsion when it should be supinating. A recipe for disaster since the overpronated foot in late midstance and propulsion is experiencing more trauma to soft tissues and bone than normal. Pain results as well as arthropathies.

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Tom Do Canto says: May 23, 2013 at 10:27 pm

Dr. Richie,

Thanks for providing references to the literature that helps to dispel the totally unfounded claims by some that foot orthoses or footwear somehow weaken the foot or lower limb.

Like you, I am also experiencing some patients of mine questioning the therapeutic benefit of foot orthoses in regard to potential foot weakness that may develop. I like to explain the tissue stress theory to my patients and explain that foot orthoses merely redistribute stress in a way that allows injured tissues to function around a more optimal level of stress to enable them to get stronger rather than weaker.

Having read these studies a while back, I appreciate the review and your commentary on their relevance to podiatry and foot orthoses.

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