The story of intrinsic foot muscle strengthening and how it was solved

Members do not see these Ads. Sign Up.

Once upon a time, as running for health reasons became more popular, a group of experts got together and helped design shoes that made running easier. Unfortunately, they did not realise that their designs also made feet a lot weaker and so the foot health of entire nations deteriorated.

At first the researchers denied any responsibility and claimed that their shoes did not impact the mechanics of the foot at all and that the foot was just as strong as it should be, but gradually other researchers showed this not to be the case and so the hunt was on for a way of putting strength back into people snoozing foot musculature.

Exercises like toe curls were used but dragging a towel towards you was found to achieve almost nothing . A world renowned fellow called Janda, invented a foot exercise called the "short foot exercise" but remarkably he failed to take into account the fact that toe flexors flex the toes! Other researchers encouraged people to do calf raises on an incline but again this was found to be entirely ineffective when it came to strengthening the intrinsic foot muscles.

Those who knew how important the foot muscles were to lower limb strength began to despair. They knew that a really effective strengthening exercise might have the ability to reduce falls in the elderly, compress morbidity in people suffering from debilitating foot conditions and even dramatically reduce injuries in recreational runners.


Eventually, a ground braking piece of research was carried out by Bruening ,Irene Davis et al 2019 and here is the key finding - If you stand favouring one foot and press your toes down you will activate intrinsic foot muscles like the abductor hallucis much more than toe curls will . However, if you place resistance in the form of an inelastic strap across the top of the foot and press the toes down, thereby levering the top of foot up against that inelastic resistance, then the activity in the abductor hallucis will be much greater than simply pressing your toes down. So at this point it was demonstrated that doming against some form of resistance was the way to target the intrinsics. To be continued .......


Below toe curl vs toe press vs doming Bruening et al

 

Anyway despite the best efforts of researchers a reliable way of strengthening the toe flexor muscles, and the intrinsic foot muscles appeared to remain elusive . Indeed, only this year a paper was published by Willemse et al that looked at muscle activation levels with various foot exercise and concluded that perhaps functional exercises might be a better option.

Here is what the concluded;
Results: Functional exercises showed larger mean EMG amplitudes than the isolated foot exercises in 25% of the 12 comparisons, while there was no difference in the remaining 75%. Conclusion: Functional exercises provoked comparable or even more activation of the PIFMs than isolated foot exercises. Given that functional exercises are easier to perform, this finding indicates the need to further investigate the effectiveness of functional exercises in physical therapy to improve muscle function and functional task performance in populations that suffer from PIFM weakness or dysfunction.

So basically the whole story about how to strengthen the intrinsic foot muscles had gone round in a circle. Not so good.

But the story has a happy ending although the solution may take some time to be universally adopted, possibly many years.

In 2021 Goldmann et al produced a paper comparing the toe flexor strength of elite female gymnasts who had trained and sprinted barefoot from an early age with the toe flexor strength of young adult male sports students. The toe flexor strength of the gymnasts was 80-90% higher than the male students. However, 7 weeks high load resistance training strengthened the males feet to the same levels as the female gymnasts( see device used below). In other words, toe flexor strength gained from years of barefoot sprinting/jumping can be replicated by just 7 weeks of targeted toe flexor strength exercise.(10 mins 4x a week) As far as I am aware the apparatus used by Goldmann is not commercially available but the Novabow System, which can be used to achieve the same ball park results, is.

 

The abductor hallucis dose not function in isolation. It functions against its antagonist. The functional antagonist is the plantaris which applies a medial ground force while the abductor hallucis is applying a lateral ground force thus griping the ground. Both have a kinematic chain of synergistic action to the functional posture of the upper body.

 

The abductor hallucis acts to abduct the hallux but is most active when plantar flexing the hallux vertically downwards. See fig C in post number 1 . If you are trying to strengthen the toe plantar flexor muscles in older people you use progressive strengthening exercises .

Toes spread out exercises are a recent idea with little chance of making real impact. Indeed , short foot ,toes spread out etc ( toe gymnastics if you like ) will all likely get very limited results.

Have you read Welte et al 2023 on arch recoil ? Probably the most important foot /ankle related paper in many years . Mobilize the medial arch in some individuals and it has implications for the entire body.

 

Further to what does and doesn't activate the abductor hallucis is a just published paper which illustrates that toe curls activate primarily the FHL, as far as the hallux is concerned, and if you want to activate the abductor hallucis then you press your big toe down.

I have not yet seen a paper that shows that the "toe spread out exercises" makes the abductor hallucis stronger ( papers showing muscle activation levels yes, actual strengthening no ), indeed, I'm not sure that spreading your toes out with the maximum force you can muster is a good idea at all.



Differences in muscle activity of extrinsic and intrinsic foot muscles in toe grip and push-down movements of the great toe


https://doi.org/10.1016/j.foot.2024.102111Get rights and content
Highlights

• •
  IPJ flexion of the great toe activates the FHL. Toe push-down activates AbdH.
• •
  The presence or absence of IPJ flexion affects the AbdH/FHL muscle activity ratio.
• •
  TP with IPJ extension position primarily activates AbdH.
• •
  Toe flexion method selection is essential for muscle strength measuring and training.

 

Good point, My findings is that I need to instruct the client to supinate the medial arch before they can activate the abductor hallucis in planter flexion. In some individuals the deeper more lateral layer is activated abducting the toe without ground contact thus further thus further aggravating the roll over onto the bunion. 3D anatomy has helped me recognize the separate action; plantarflexion pulling on the medial arch and the abduction pulling on the distal metatarsal heads which in pronation do not have good ground force but may have strong dorsiflexion to pull against.

 

Hi Hans,

I agree with you. Axiomatically, you lose intrinsic muscle strength when the foot operates in gravity drive (abnormal) pronation. If you intentionally supinate the ILA, you are reversing the impact of gravity drive pronation.

There are more efficient ways of achieving increased muscular strength in the foot then having your client supinate their ILA.

• Isolate the cause of gravity drive pronation and attenuate it.

 

Precisely: That is what my part of the team is. When James Mc Alexander gave me a ride home when he was leaving his podiatry office and I explained what we were trying to do in the chiropractic office, he exclaimed, I need you; I am only trained up to the knee. Any posture distortion will show up in the feet. One client had a wry neck and could not lift his chin from his left shoulder. Walk around that way for awhile and see what you fell in your feet.

 

Global postural distortions can be ascending, starting in the feet, or descending, starting in the skull, spine, or pelvis.

I have been a strong advocate of podiatrists working with chiropractors. I published a paper in 1988 that I coauthored with a DC.

I congratulate both of you for thinking out of the box.

 

Hi Hans
A number of good quality research papers are now indicating that medial arch recoil during gait is critical to the functioning of the skeleton as a whole. In fact, arch recoil may often be at least as important as factors around arch pronation during weight acceptance .

What Welte et al have found is that the arch recoils as gait progresses and this helps keep the tibia ( and, in another paper ,a group says also pelvis) orientated for efficient gait .

Positive foot power does not propel the body forwards but keeps the tibia more upright allowing far better function at the ankle ,pelvis etc.

For recoil to happen, adequate power (from the intrinsic muscles, for example ) must be generated/ returned and the foot must be able to properly flex around the cuneonavicular joint. Shut down this joint and we walk a bit like chimpanzees.

How would you go about mobilizing the cuneonavicular joint, remembering it could prove to be one of the most important in the human body ?

Not sure how a modified Morton's extension would affect arch recoil/mobility. Not a lot, probably.

 

Medial arch recoil is a function of STJ function. If the STJ is pronated past midstance, the ILA will not recoil.

 

The problem we had with this was they were using a wedge which made the big toe slide latterly and made the problem worse.

 

If the medial wedges are too severe the patient will slide laterally off the wedge. If the medial wedge is too wide, impinging on the second or lateral metatarsal heads, it will be uncomfortable or even painful to the paient.

There are specific tests used to determine the foot pathology one is dealing with and how to properly dimension the wedges. Thus dimensioned (as determined by the LRT and muscle testing), the patient will not slide laterally and the insoles will be transparent.

In a prior post I downloaded photos demonstrating how to dimension the insole used to stabilize the PreClinical Clubfoot Deformity. The proprioceptive insoles sold by a company in Tacoma Washington are used to treat RFS (Rothbarts Foot).

 

There is a close relationship but could you point me in the direction of any published work that says "Medial arch recoil is a function of STJ function." (Other than your own that is, since to the best of my knowledge, you have never published a randomized controlled trial. )

Brian ,what are the variable features of your insole . Is it just the height of the wedge ?

Could you answer this bit Hans ? Little has been written about mobilizing the cuneonavicular joint .

 

ILA recoil linked to gravity drive pronation is based on my research. I gave many video examples on my research webpage which was discontinued when I retired.

Regarding the dimensioning of the insole I used to stabilize the PreClinical Clubfoot Deformity, on a prior thread I downloaded photos giving those specs.

 

As far as I can see , it's generally only you propping up any of your work . "Many video examples " ,then down comes the site , no more video examples ,etc.

 

I have heard this same criticism on this forum regarding my research.

In 2002 I first published on two previously unknown foot structures (RFS and PCFD). I linked the etiology of RFS to high talar torsion angles which cascaded down the entire medial column of the foot. I termed this structural aberration medial column supinatus.

For nearly 20 years, on this forum, Podiatrists criticized my embryological research (in very unprofessional obloquy), challenging the existence of medial column supinatus. Stating I was the only one publishing on this structural twist.

• First forward 20 years, other researchers, using WBCT, have proven medial column supinatus does indeed occur in the human foot.

So yes, right now I am the only one linking the lack of ILA recoil to gravity drive pronation. But I am sure in time other researchers will come to the same conclusion.

 

Just words that can't really be justified , Brian . However, I wish you a long and happy retirement .