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EXTRINSIC toe flexor strength is not related to postural stability during static ...

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Aug 17, 2019.

  1. scotfoot

    scotfoot Well-Known Member

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    This thread relates to a paper by J Yamauchi et al 2019 ( below ) .

    Why is it that some groups of scientists , studying the foot , insist on measuring toe flexor strength using toe grip type dynamometers and seem to assume readings
    will accurately reflect the strength of the intrinsic toe flexors ?
    They won't . They measure extrinsic toe flexor strength , a very different beast when it comes to static balance .

    Here are the highlights of their paper ,all of which , in my opinion ,are not substantiated by their paper due to the measurement technique used .

    Toe flexor strength (TFS) was measured as an indicator of foot muscle strength.

    TFS and foot arch height (FAH) were not significantly correlated.

    TFS was not related to COP variables in double- or single-leg standing.

    FAH was not related to COP variables in double-leg standing.

    TFS has no significant role in maintaining static postural stability.

    Toe flexor strength is not related to postural stability during static ...


    by J Yamauchi - ‎201930 Jul 2019 - Because the toe flexor muscles help to support the foot arches, they might be an important contributor to postural stability. However, no research has identified the influence of the toe flexor strength or the foot arch height on postural stability in static upright standing.
    Last edited: Aug 17, 2019
  2. efuller

    efuller MVP

    A couple of points.
    I think they are using the keeping the body upright definition of postural stability. I have heard others describe maintaining arch height as posturally stable.

    The title of their article was Toe flexor strength is not related to postural stability during static upright standing in healthy young individuals

    Leaving off the last few words makes a big difference.

    I would assume that healthy young individuals are not routinely falling over. One should compare the strength of young healthy subjects to subjects that routinely fall over. (Are these people falling over because of weak muscles or a bad vestibular system? Those with a bad vestibular system might have normal strength.)

    One could also question whether toe flexor strength is the rigth thing to measure for being able to keep upright. That is more dependent, in double limb stance, on ankle plantar dorsi and plantar flexors. One could easily have weak toe flexors and strong enough ankle dorsiflexors and plantar flexors to move the center of pressure under the foot to maintain balance.
  3. scotfoot

    scotfoot Well-Known Member

    One study that shows the short foot exercise improves postural stability in young adults can be found at the link below (1) . Of course the problem with this is that the short foot exercise is primarily an exercise for the extrinsic foot muscles despite peer review continually mistaking it for an exercise of the intrinsic foot muscles and not the extrinsics .

    A better paper that demonstrates the link between intrinsic muscle morphology and balance in recreational runners can be found here (2) .

    Differences in static-and dynamic-balance task performance after 4 ...


    by SK Lynn - ‎2012 - ‎Cited by 72 - ‎Related articles2012 Nov;21(4):327-33. Epub 2012 Jun 18. Differences in static- and dynamic-balance task performance after 4 weeks of intrinsic-foot-muscle training: the short-foot exercise versusthe towel-curl exercise. Lynn SK(1), Padilla RA, Tsang KK.


    Foot muscle morphology is related to center of pressure sway and control mechanisms during single-leg standing.

    Zhang X1, Schütte KH2, Vanwanseele B3.
    Author information


    Maintaining balance is vitally important in everyday life. Investigating the effects of individual foot muscle morphology on balance may provide insights into neuromuscular balance control mechanisms. This study aimed to examine the correlation between the morphology of foot muscles and balance performance during single-leg standing. Twenty-eight recreational runners were recruited in this study. An ultrasound device was used to measure the thickness and cross-sectional area of three intrinsic foot muscles (abductor hallucis, flexor digitorum brevis and quadratus plantae) and peroneus muscles. Participants were required to perform 30s of single-leg standing for three trials on a force plate, which was used to record the center of pressure (COP). The standard deviation of the amplitude and ellipse area of the COP were calculated. In addition, stabilogram diffusion analysis (SDA) was performed on COP data. Pearson correlation coefficients were computed to examine the correlation between foot muscle morphology and traditional COP parameters as well as with SDA parameters. Our results showed that larger abductor hallucis correlated to smaller COP sway, while larger peroneus muscles correlated to larger COP sway during single-leg standing. Larger abductor hallucis also benefited open-loop dynamic stability, as well as supported a more efficient transfer from open-loop to closed loop control mechanisms. These results suggest that the morphology of foot muscles plays an important role in balance performance, and that strengthening the intrinsic foot muscles may be an effective way to improve balance.


    Abductor hallucis; Closed-loop control; Open-loop control; Peroneus muscles; Stabilogram diffusion analysis

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