Do Foot Orthoses Cause Muscle Weakness?

Thank you to Dr Doug Richie for this guest post

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 my ‘Who Is Fact Checking The Podiatric Profession’ for Podiatry Today blog post).

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-a… .
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.