A fascinating paper on the mechanics of gait.

[Gerrard Farrell]

1. A paper was just published by Lauren Welte et al https://doi.org/10.3389/fbioe.2023.1155439 . I found it fascinating and so discussed it in a few posts placed on "Podiatry Arena" . These are copied below.
   
   
   Apparently, medial arch flexibility, and flexibility at the Navicular/medial Cuneiform joint in particular, may be key to upright gait . A well written summary of recent research can be found via the link provided . https://www.popsci.com/health/foot-a...man-evolution/
   
   Basically this -
   Tibia sits on Talus .
   Heel lifts and arch flattens so upper surface of talus and tibia point forwards .
   Arch tissues reestablish more arched foot shape by recoil/intrinsic foot muscle contraction.
   Tibial aspect of talus now points more vertically, tibia also more upright.
   
   
   
   
   scotfootWell-Known Member
   The paper to which the previous post refers was recently published by Lauren Welte et al https://doi.org/10.3389/fbioe.2023.1155439
   
   Here are a couple of quotes from a review of the paper -
   
   “We thought originally that the spring-like arch helped to lift the body into the next step,” study co-author and University of Wisconsin-Madison biomechanical engineer Lauren Welte said in a statement. “It turns out that instead, the spring-like arch recoils to help the ankle lift the body.”
   
   So it could be that one of the roles of the intrinsic foot muscles (among many ) is not about propelling the COM forwards but facilitating the ankle in this role . The intrinsics are required to put the tibia in the correct position at toe off . The intrinsics don't need to be big powerful muscles to do this but they must be strong enough and work alongside a flexible arch.
   
   "Surprisingly, they found that a rigid arch without recoil caused the foot to prematurely leave the ground, likely decreasing the efficiency of the calf muscle. A rigid arch also leaned the ankle bones too far forward. A forward lean looks more like the posture of walking chimpanzees instead of the straight upright stance of a human gait."
   
   
   Figure 1
   
   FIGURE 1. (A) The center of mass (COM) propulsion hypothesis suggests that both arch recoil and the foot’s levering ability can raise the COM. (B) The foot levers around the fulcrum metatarsophalangeal joint.
   An alternative hypothesis to explain the role of late stance foot arch recoil is that its shape and plantarflexion mobility are critical for allowing the ankle and proximal segments to achieve postures required for efficient locomotion (Lim and Park, 2018)
2. scotfootWell-Known Member
   A recent paper on foot core strengthening found that this type of exercise could reduce running injuries of the lower limb by half.
   
   Might it be that strengthening the arch supporting muscles of the foot helps with arch recoil/recovery close to toe off and allows a more favourable orientation of the tibia to be achieved ? Runners with stronger feet run with a more upright tibia and not with the tibia tending towards a more chimpanzee like orientation?
   
   Interestingly ,if you take the IFM out of the equation using an LA block, runners can still manage but use a more pronounced "hip swinging strategy".
   
   A number of papers have shown strengthening the IFM can help with PFP in the knee .
3. scotfootWell-Known Member
   scotfoot said: ↑

   .

   
   Another mechanism which helps arch recoil/recovery is the windlass mechanism . As the toes dorsiflex near toe off the PF wraps around the met heads and helps re-establish a more pronounced medial arch .
   
   But what if shoes have toe springs . These allow the foot to move through toe off with less toe dorsiflexion which presumably means less windlass activity, less pronounced medial arch, and a less favorably orientated tibia. And that might lead to problems!
   
   
   #4
4. scotfootWell-Known Member
   So Welte et al feel that the navicular /medial cuneiform joint is key to medial arch flexibility and this this flexibility may in turn be key to tibial orientation through toe off . So you need energy storing tissues and a functional joint to give effective arch recoil .
   
   But what of conditions that affect joint mobility such as diabetes (glycation of ligaments ) ,arthritis and even aging. How can a non mobile navicular /medial cuneiform joint be mobilized ?
   
   
   Last edited: Jun 12, 2023 Name - Gerrard Farrell creator of the "Novabow System"
   Profession - Dentist
   Location - Glasgow , Scotland
   Interest in podiatry - Patents and a patent application related to a "foot exercise and strengthening device".
   scotfoot, Jun 12, 2023
   #5

[Gerrard Farrell]

A reasonable question might be - if you wear shoes and the intrinsic foot muscles develop a certain level of strength that reflects the demands placed upon them in the shod state, why would any strengthening be required to reduce injury risk in, for example, runners.? I believe the paper by Welte et al, https://doi.org/10.3389/fbioe.2023.1155439 ,may container the answer .

Briefly, the intrinsic foot muscles retain their strength by being stimulated during heel off through toe off. If you take work away from them by providing a downward force via a stiff soled shoe, then they will be less active and get weaker. Weaker, less active, intrinsics mean less recoil of the arch through toe off and a less vertical tibia, creating problems and compensations throughout the kinetic chain.

Without shoes the toes must press down into the substrate to prevent rotations around the ball of the foot during the right past left ,left past right action that characterises gait. Here is a link to brief youtube video that shoes the toes resisting rotation around the ball of the foot.

https://youtube.com/shorts/SorZTV7CZ9Q?si=7S1y9VBNp8xxlzVZ

[Gerrard Farrell]

Looking further at the paper of Welte, Rainbow et al ,if arch recoil is important in the optimal orientation of the tibia through toe off, then do people with pes cavus feet ( high medial arches ) have any kind of athletic advantage over those other foot types?

Here is a quote from a recent research paper concerning this question.


"Conclusion

Short distance runners with high arch foot have improved dynamic balance and speed when compared to low and neutral arch foot."

Does seem to fit !


J Orthop. 2018 Mar; 15(1): 114–117.
Published online 2018 Feb 2. doi: 10.1016/j.jor.2018.01.050
PMCID: PMC5895915
PMID: 29657452 Impact of various foot arches on dynamic balance and speed performance in collegiate short distance runners: A cross-sectional comparative study

Selvaraj Sudhakar,^a,⁎ S. Veena Kirthika,^a K. Padmanabhan,^a G. Mohan Kumar,^a C.V. Senthil Nathan,^a R. Gopika,^a and Asir John Samuel^b,⁎