Shod populations have very weak feet, even the athletically active.

[Gerrard Farrell]

This abstract was just published on the internet (below) . It dropped my jaw .

Basically , adolescent female gymnasts where found to have 80-86 % greater toe flexor strength than adult male sports students, so, on average, a 5ft 2 inch,100 pound girl, had toe flexors far stronger than a 5ft 11, 180 pound , athletic, active, young adult male . That's like finding a new species of mouse that kicks harder than a kangaroo .


Recently Isabel Sacco and her team produced a paper showing that strengthening the foot core more than halved running related injuries . In light of the this most recent Goldmann paper that starts to make sense .

Researchers take the toe flexor strength of healthy individuals in a given group, to be the norm . But it now looks like the "norm" is only about half of natural levels !


Toe flexor strength in elite female gymnasts compared to toe flexor strength-trained men

• Jan-Peter Goldmann
• Marvin Zedler

Details

Introduction
There is some evidence that intrinsic foot muscles propel the body forward during locomotion [1]. Nearly 80% of intrinsic foot muscles consists of toe flexor muscles (TF) [2] proceeding from the heel to the distal phalanges of the toes. TF’ strength capacity has the potential to enhance jump performance [3]. Since the ability to jump is a performance-limiting factor in gymnastics, we hypothesized that elite female gymnasts’ TF strength is higher than in male sport students, but similar to TF strength-trained men.

Methods
28 female gymnasts (15 ± 2 y, 47 ± 9 kg, 1.56 ± 0.09 m) of the German national team and a basic control group of sport students (n = 28, 25 ± 3 y, 77 ± 8 kg, 1.83 ± 0.06 m) performed three maximum voluntary isometric contractions (MVC) of TF for each foot. TF strength was determined by measuring the moment about the transverse axis of a custom-made dynamometer in 25 degrees toe dorsiflexion. The external moments of force about the axis represented the moments of force produced by the TF [3]. The best of three trials was used for further analysis. Peak moments were determined as the mean value of a 2 s time window of the plateau region. Data were compared to a previous study with the same dynamometer, where a TF strength training group (15 men, 24 ± 4 y, 77 ± 9 kg, 1.85 ± 0.07 m) performed a heavy resistance TF strength training with 90% of MVC for 7 weeks [3]. Statistics: Kolmogorov-Smirnov, unpaired t-test.

Results and Discussion
TF strength significantly differed (p < 0.001) between elite female gymnasts (left: 0.41 ± 0.08 Nm kg-1, right: 0.45 ± 0.09 Nm kg-1) and male sport students (left: 0.22 ± 0.05 Nm kg-1, right: 0.25 ± 0.06 Nm kg-1). There were no significant differences (p > 0.05) between the TF strength of elite female gymnasts and the male strength training group after 7 weeks of TF strength training (left: 0.38 ± 0.07 Nm kg-1, p = 0.07, right: 0.40 ± 0.08 Nm kg-1, p = 0.07).
Adolescent female gymnasts showed 80% to 86% higher TF strength than male sport students, but nearly the same strength level as adult men after 7 weeks heavy resistance TF strength training [3].

Conclusions
TF in elite gymnastics seem to be highly loaded and have to be of particular interest for training and performance enhancement.

[Gerrard Farrell]

Delving deeper , an interesting new study compared the effects of 2 different exercise protocols on subjects with knee pain .

Group 1- hip and knee strengthening

Group 2- hip, knee and foot strengthening .

Only group 2 ,the group which did foot strengthening exercises, showed a significant reduction in knee pain.

Also worth noting that in study group 1, subjects had increased hip flexor muscle mass at the end of the exercise period ( not a surprise ) but that group 2 had a significantly greater increase in this mass than group 1 (foot strengthening seems to have affected the hip musculature ) .

It seems to me that whether you are studying the foot, ankle, knee or hip, you ignore foot strength to the detriment of your studies .

What happens at the foot echoes along the kinetic chain . Loudly


Link to paper

!Short foot exercises have additional effects on knee pain, foot biomechanics, and lower extremity muscle strength in patients with patellofemoral pain

Pınar Kısacık ¹, Volga Bayrakcı Tunay ¹, Nilgün Bek ², Özgür Ahmet Atay ³, James Selfe ⁴, Aynur Ayşe Karaduman ²
Affiliations expand

• PMID: 34024814
• DOI: 10.3233/BMR-200255

[Gerrard Farrell]

Looking at the two posts above ,it might reasonably be argued that it is the activity and its frequency which causes the toe flexor strength of elite adolescent female gymnasts to be so much stronger than their adult male counterparts, and not the barefoot nature of this activity.

However, this opinion is countered by the work Nihal et al 2002 ,which found that the toe flexor strength of professional dancers was only slighter higher than non dancers ( a lot of gymnastics is dance based except asymmetric bars which has very little footwork other than the landing ) .

In the same year, 2002, Endo et al found that toe flexor strength was 39.1% greater in men than women but also found -

" However, when normalized by body size (body weight × height), the gender difference in strength no longer reached statistical significance."

So toe flexor strength varied with weight and height .

Elite, adolescent, female gymnasts are ,on average shorter than average height and much lighter . In the UK, a mature woman is about 5 feet 3 inches and 154 pounds .The average height of an elite gymnast is 5 feet 1 and less than 100 pounds .

Given that Endo found that toe flexor strength is closely related to height and weight you might expect smaller and much lighter gymnasts to have lower toe flexor strengths than much larger average women. But they don't , they have toe flexor strengths 80-86 % higher than adult male sports students .Amazing !

[Edmund Cramp]

I think these results could lead to an interesting study - I wonder if the initial walking activity as a young child could influence not just the muscles but the interactions within the feet, does barefoot walking as a child result in slightly stronger muscles but also a better control of the the muscle interactions that leads to these results? I think that there was a study many years ago that saw slightly different gait in children raised in South America (and raised walking barefoot), compared to the results in David Sutherland's The Development of Mature Walking that described gait in North America.

[Gerrard Farrell]

Research indicates that habitually unshod children have better balance than the habitually shod, particularly between the ages of 6-10, but whether such individuals develop more proprioceptive nerve endings, which are then retained into adulthood is ,as far as I am aware, unknown .

It has been shown that strengthening exercises around the shoulder, knee and ankle improves proprioception around those joints .

Mickle et al have shown that targeted strengthening of the foot in an elderly population can restore toe flexor strength to near younger adult levels and improve single leg balance . It seems likely that the balance improvement will be due to increased strength and proprioception .

It has been demonstrated that the intrinsic foot muscles are linked to the vestibular apparatus with regard to postural control . It has also been demonstrated that the nerve endings in the sole of the foot also have a large role to play in this .

In diabetic neuropathy there is often intrinsic foot muscle atrophy along with loss of sensation in the foot, and these factors are likely strongly linked to the up to x 20 increased risk of falls in these subjects ( yes 2000% ) . Interestingly, resent research has shown that targeted foot exercise can reverse neuropathy and intrinsic foot muscle atrophy . If such exercises can in part reverse the process then what if it where employed as soon as intrinsic atrophy was detected ?

Some time ago Prof Irene Davis and her colleagues wrote about the "foot core " . I have included a link direct to the relevant section of the paper, but the bit I really like is the realisation that the intrinsic foot muscles are ideally orientated to detect early changes in COP . Better even than the ligaments ,tendons and muscles of the ankle, IMO . Thus, to improve proprioception in the foot is to do so for the body as a whole .

link https://bjsm.bmj.com/content/49/5/29...k%20posture.47

[Gerrard Farrell]

Further evidence that the feet in shod populations are much weaker than "natural levels", has recently been produced by Dr Chris D'Aout and his colleagues from Liverpool University

Below is a link to the paper which demonstrates that shod feet are weakened by the splinting action of shoes and that merely walking about in minimal shoes can restore some of the strength deficits .

I am not a fan of running on concrete without a bit of padding between me and the ground, but it certainly seems like --

1 People that wear supportive shoes all day will have feet at least 60% weaker than nature intended .

2 Runners that strengthen their feet but continue to use their supportive bulk shoes will still more than half their injury rate ,on average .



Quote
"This study shows that foot strength increases by, on average, 57.4% (p < 0.001) after six months of daily activity in minimal footwear"

Link
Daily activity in minimal footwear increases foot strength https://pubmed.ncbi.nlm.nih.gov/34545114/ pic.twitter.com/oYsmyc1zQp

[Edmund Cramp]

Thanks Gerrard, I think that this is a very interesting discussion, I had never thought about this before but as a young kid, after reading Frank Herbert's novel Dune when it was first published, I was intrigued by Paul Atreides being told that you were safer barefoot than wearing shoes. So every summer I would run barefoot on the rocks around the base of cliffs and then up and down the cliffs in Wales all the time - I never fell over and now I wonder if it gave me much better foot control.
One year, in the early 90's when I was setting up a gait lab in Springfield Illinois, the user told me that she wanted to look at the results when someone stood on one leg on the force plate with their eyes closed and so we setup a test session. They were amazed when it turned out that I could stand on one leg with my eyes closed for a much longer time then everyone else. Now I wonder if it was just a result of running parkour-like over the rocks for years as a kid when my feet would have been growing.

[Gerrard Farrell]

Hi Edmund

The film Dune crosses my mind every time I see a seagull stamping on the grass of the golf course trying to bring worms to the surface ( it works apparently ,with the worms reacting to the vibrations) .

In terms of why your balance is better than others it may be down to a number of factors but toe flexor strength seems to be one of the keys . It could be that the shoes you wear are more minimal than other types with less heel drop ,toe spring ,arch support and general cushioning .

Re the D'Aout paper a 57% strength difference is a lot . I strongly suspect that moving around for 6 months barefoot, rather than in minimal shoes, would give strength differences of 100% or more .

One question researchers have been asking for some time is, are weaknesses in the intrinsic foot musculature related to the development of plantar fasciitis . It's difficult to get a clear answer for this if the population group you are studying, with PHP or without ,all have very weak feet to start with . The assumption that the toe flexor strength of a health habitually shod young adult is the norm is clearly very far from the mark .It is merely the splinted norm .

[Gerrard Farrell]

Why should modern shoes cause the toe flexors to be only half as strong as natural levels and what difference does it make .

The supportive elements of shoes are not, IMO, the cause of foot weakness but instead it is the stiff natured soles of modern shoes and the excellent traction they provide that has taken work away from the toe flexors and produced weakness .
Here is an extract from a previous thread of mine on biomch-l


"You might be interested in the following .It relates to grip ,torque ,flat rigid surfaces and the unshod condition .

First I found myself a suitable surface such as linoleum . Next I took off my shoes and socks and stood next to a wall for support . Then , taking most of my weight initially on the right foot which was kept flat on the ground ,I put my left foot into toe off position so that only the ball of the foot and the toes were in contact with the ground . Then I carefully transferred some weight onto the left foot and finally, with the ball of the foot and toes under some pressure , rotated the foot outwards producing torque . I found that the toes played an important part in resisting the outward rotation and that they also began to become spaced out from each other possibly engaging the adductors .( please note that I am not suggesting that anyone copy the above exercise sequence or injury may result )
So perhaps the toes can significantly aid grip on a flat rigid surface ?"

Further to the above, rigid ,modern , shoes will bend around the MTFJ during push off but the resilience of the sole will tend to press the anterior part of the sole into the ground . This elastic resilience, coupled with traction of a rubber sole means that the toe flexors don't need to do as much work as they would with an unshod foot or with the less resilient sole of a minimal shoe .

Why strengthen weak feet . Because Sacco et al found it halves injury risks in recreational runners .

Surely I am not the first to realise that the toes and toe flexors are required to push into the substrate to prevent rotation about the ball of the foot during the push off phase of gait . There must be material written about this somewhere in which case I would be grateful for any link that could be provided .