The functional importance of human foot muscles for bipedal locomotion
Dominic James Farris, Luke A. Kelly, Andrew G. Cresswell, and Glen A. Lichtwark PNAS
January 17, 2019
Apparently the group who produced the paper mentioned in the first post have another coming out next week . I hope its related to the intrinsics and balance .
Some time ago I advanced a grounded
theory about the role of the intrinsics in balance
(see below ) .
It would be fascinating to see if the theory is still plausible following nerve block scrutiny .
So the new paper is out and its not about nerve blocks and balance (see 2 below )
.This is a bit disappointing but the new paper is still of interest ,not least for the following quote -
"We found that the underlying passive visco-elasticity of the foot is modulated by the muscles of the foot, facilitating both dissipation and generation of energy depending on the mechanical requirements at the centre of mass (COM). "
In my opinion , although the researchers might not agree
,we are getting closer and closer to the idea of the tissues that lie between the bony arch of the foot and the plantar fascia ,being compressed during gait .The visco-elasticity of the muscular component of this tissue
can be controlled by muscle contraction . There is no reason why muscle cannot act as a skeletal component . For example , the muscular hydrostat .
The foot is more than a spring: human foot muscles perform work to adapt to the energetic requirements of locomotion
Ryan Riddick , Dominic J. Farris
and Luke A. Kelly JOURNAL OF THE ROYAL SOCIETY INTERFACE:23 January 2019
This relates to the paper by DJ Farris et al 2019 "The functional importance of human foot muscles for bipedal locomotion " , introduced in the first post
.
In this paper the authors opine -
"It is also conceivable that extrinsic foot muscles (e.g., tibialis posterior, tibialis anterior, and the peroneals) could provide some support to the LA, and potentially might have compensated for the intrinsic muscles in the nerve block condition. However, the anatomical path of the tendons of the extrinsic foot muscles suit them more to providing support in the frontal plane of the foot. Furthermore, their small moment arms about the LA hinders their potential to generate supporting moments. It is therefore doubtful that the extrinsic foot muscles could compensate, but this requires further investigation. "
Based on what is now known , I disagree with "It is therefore doubtful that the extrinsic foot muscles could compensate " and instead believe it is actually likely that the extrisic muscles could and do compensate for intrinsic contribution deficit .
Continuing on the subject of the Farris et al 2019 paper , and not withstanding the authors' arguments about the short moment arms of the extrinsic foot muscles and their tendency to produce movement in a frontal plane , the tibialis posterior muscle is regarded as a major stabilizer and supported of the MLA . There is no reason why this muscle could not take on a greater role, during midstance, when other arch supporting elements fail . No reason at all .
It is worth
pointing out that the section of text in the paper which casts doubt on the possibility of the extrinsic picking up the work normally done by intrinsics, is without references.
Further to Farris et al 2019, some time ago Kevin Kirby produced a paper " The load sharing system of the longitudinal arch of the foot " which teaches towards a degree of redundancy being built in to the arch and its supporting structures and allows for a failure of one part of the system to be compensated for by others .
I agree with this but more to the point , so does the evidence.
For example , in Morten Bilde Simonson et al 2019 , the contribution of the tibialis posterior muscle to foot stability and support was impaired by injecting a pain causing saline solution into the muscle . The researchers found that reduced output from the tibpost was compensated for by increased work from the flexor digitorum longus and flexor hallucis longus.
Continuing on the general theme of Farris 2019 , an important piece of research , there is more direct evidence that changing the force generating capacity of the intrinsic foot muscles will lead to changes in the forces generated in other extrinsic arch supporting muscles .
Subsequent to Farris 2019 the following
paper was published ;
Effects of a 4 week short foot exercise programme on gait characteristics in patients with stage 11 posterior tibial tendon dysfunction .
Basically ,the authors wondered if increasing the activity of the intrinsic foot muscles would reduce the amount of force being generated by the extrinsics during gait . It did .
Here is part of the abstract ; Abstract
Context: Clinically, it has been suggested that increased activation of intrinsic foot muscles may alter the demand of extrinsic muscle activity surrounding the ankle joint in patients with stage II posterior tibial tendon dysfunction. However, there is limited empirical evidence supporting this notion. Objective: The purpose of this study was to investigate the effects of a 4-week short-foot exercise (SFE) on biomechanical factors in patients with stage II posterior tibial tendon dysfunction. Design: Single-group pretest-posttest. Setting: University laboratory. Participants: Fifteen subjects (8 males and 7 females) with stage II posterior tibial tendon dysfunction who had pain in posterior tibial tendon, pronated foot deformity (foot posture index ≥+6), and flexible foot deformity (navicular drop ≥10 mm) were voluntarily recruited. Intervention: All subjects completed a 4-week SFE program (15 repetitions × 5 sets/d and 3 d/wk) of 4 stages (standing with feedback, sitting, double-leg, and one-leg standing position).
Conclusions: Our 4-week SFE program may have positive effects on changing muscle activation patterns for tibialis anterior and fibularis longus muscles, although it could not influence their structural deformity and ankle joint moment. It could produce a potential benefit of decreased tibialis posterior activation.
Foot stiffening during the push-off phase of human walking is linked to active muscle contraction, and not the windlass mechanism
Farris, D; Birch, J; Kelly, L Source: 2020
With regard to the latest Farris paper , ongoing research into the foot seems to throw up more plot twists than an Agatha Christie novel .
I look forward to reading the full paper once it is published but for the moment find it intriguing that the windlass mechanism does not seem to be the main tensioner of the plantar fascia during push off .
Makes me wonder whether treatments like the Strassburg sock ,used for plantar fasciitis , produce a therapeutic effect by stretching the plantar fascia or the intrinsic foot muscles .
A fairly recent paper indicated that the plantar fascia stretch ( dorsiflexing the toes ) is more effective for plantar fasciitis than calf stretches
which perhaps suggests a muscular origin for at least some cases of "plantar fasciitis " .
Three-dimensional Motion of the Toes with Simulated Contraction of Individual Toe Flexors and Extensors: A Cadaver study
Keisuke Negishi et al The Foot 24 July 2023, 102044