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The foot as a lever :Factors influencing stiffness and efficiency

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Jul 28, 2022.

  1. scotfoot

    scotfoot Well-Known Member


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    Even in the greatly weakened state that habitual use of modern shoes causes, the intrinsic foot muscles significantly contribute to foot stiffness and leverage at the ankle in a way that improves vertical jumping.

    .Conclusion: In addition to their known role of regulating the energetic function of the foot, our data indicate that the intrinsic foot muscles also act to optimize ankle joint torque production and leverage during the propulsion phase of vertical jumping.


    Examining the intrinsic foot muscles' capacity to modulate plantar flexor gearing and ankle joint contributions to propulsion in vertical jumping


    Ross Smith 1, Glen Lichtwark 2, Dominic Farris 3, Luke Kelly 2
    Affiliations expand
    Free article
    Abstract

    Background: During human locomotion, a sufficiently stiff foot allows the ankle plantar flexors to generate large propulsive powers. Increasing foot stiffness (e.g., via a carbon plate) increases the ankle's external moment arm in relation to the internal moment arm (i.e., increasing gear ratio), reduces plantar flexor muscles' shortening velocity, and enhances muscle force production. In contrast, when activation of the foot's intrinsic muscles is impaired, there is a reduction in foot and ankle work and metatarsophalangeal joint stiffness. We speculated that the reduced capacity to actively control metatarsophalangeal joint stiffness may impair the gearing function of the foot at the ankle.
    Methods: We used a tibial nerve block to examine the direct effects of the intrinsic foot muscles on ankle joint kinetics, in vivo medial gastrocnemius' musculotendinous dynamics, and ankle gear ratio on 14 participants during maximal vertical jumping.
    Results: Under the nerve block, the internal ankle plantar flexion moment decreased (p = 0.004) alongside a reduction in external moment arm length (p = 0.021) and ankle joint gear ratio (p = 0.049) when compared to the non-blocked condition. Although medial gastrocnemius muscle-tendon unit and fascicle velocity were not different between conditions, the Achilles tendon was shorter during propulsion in the nerve block condition (p < 0.001).
    Conclusion: In addition to their known role of regulating the energetic function of the foot, our data indicate that the intrinsic foot muscles also act to optimize ankle joint torque production and leverage during the propulsion phase of vertical jumping.
     
  2. scotfoot

    scotfoot Well-Known Member

    Of course there are a number of structures that contribute to foot stiffness during push off including the extrinsic foot muscles, the ligaments of the foot that connect its many bones, and the plantar fascia.

    Changes in the configuration of the bones of the foot themselves also help make it a more rigid lever, with heel off producing a narrowing of the forefoot and a more pronounced transverse arch.

    But returning to Smith et al 2021 , can strengthening weak feet ( just about everybody's if they wear modern shoes ) improve athletic performance ? A number of studies have shown that strengthening the foot can improve sprinting speed ,standing long jump, standing vertical jump, and single leg balance .

    One study reports that foot strengthening can half running injuries and a number point to intrinsic foot muscle strengthening helping runners avoid knee pain ( PFP) .

    If you are a sports podiatrist surely foot strengthening would be a central recommendation for almost everyone with biomechanical problems related to the foot?( Obviously caution is advised around some conditions like diabetes etc )
     
  3. scotfoot

    scotfoot Well-Known Member

    It's all very well banging on about the benefits of strengthening the foot but how do you get people to do this effectively and on a regular basis?

    For younger individuals, walking in minimal shoes for can work wonders with toe flexor strength increasing by 57% in one six month study . But can people be persuaded to wear minimal shoes in favour of shoes which make them 1-3 inches taller and or which feel more comfortable. And can wearing minimal shoes increase toe flexor strength in people over sixty when muscle mass loss is underway throughout the entire body? Nobody knows.

    (As an aside, the most promising study I have seen re injury prevention in recreation runners involved foot strengthening exercises and normal modern running shoes. )

    If you are going to get people, and most importantly older people, to strengthen their feet, exercises need to be easy, say 5 mins 2x per week , and the primary exercise must be about pressing the toes DOWN . Toe curls are about the extrinsic toe flexors not the intrinsics and won't help with this important aspect of foot strengthening.

    Actually, I can think of only one instance of athletes curling their toes to give better grip on a substrate and that is when swimmers start a race from elevated starting blocks. Otherwise feet don't grip like a hand would ,they have evolved for a different purpose.
     
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