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The importance of the foot muscles.

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Oct 16, 2022.

  1. scotfoot

    scotfoot Well-Known Member


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    Until now I had always thought that the extrinsic foot muscles would likely have a considerably greater role to play in actually propelling the body than the intrinsic muscles. However, my perception has been altered by the paper below.

    It would appear that during hopping on a dampening surface ( a surrogate for running since its easier to make measurements ) the intrinsic foot muscles perform 25 % of the active work done at the ankle. As far as I can tell that's roughly the same as the active contribution made at the knee or hip joints.

    Good grief ,who knew?

    Neuromechanical adaptations of foot function when hopping on a damped surface

    Jonathon V Birch 1 2, Dominic J Farris 1, Ryan Riddick 2, Andrew G Cresswell 2, Sharon J Dixon 2, Luke A Kelly 2
    Affiliations expand
    Free article
    Abstract

    To preserve motion, humans must adopt actuator-like dynamics to replace energy that is dissipated during contact with damped surfaces. Our ankle plantar flexors are credited as the primary source of work generation. Our feet and their intrinsic foot muscles also appear to be an important source of generative work, but their contributions to restoring energy to the body remain unclear. Here, we test the hypothesis that our feet help to replace work dissipated by a damped surface through controlled activation of the intrinsic foot muscles. We used custom-built platforms to provide both elastic and damped surfaces and asked participants to perform a bilateral hopping protocol on each. We recorded foot motion and ground reaction forces, alongside muscle activation, using intramuscular electromyography from flexor digitorum brevis, abductor hallucis, soleus and tibialis anterior. Hopping in the Damped condition resulted in significantly greater positive work and contact-phase muscle activation compared to the Elastic condition. The foot contributed 25% of the positive work performed about the ankle, highlighting the importance of the foot when humans adapt to different surfaces.
     
  2. scotfoot

    scotfoot Well-Known Member

    During hopping 2/3 rds of the active work done is done at the ankle and 1/3 at the knee joint and hip joint combined.

    Of all that work done at the ankle 25% is being done by the intrinsic foot muscles and that's in individuals with weak intrinsics.

    It strikes me that strengthening the intrinsics to more natural unshod levels might substantially reduce the work the calf muscles have to do and also reduce stress/strain in the achilles tendon during hopping/ running .
     
  3. scotfoot

    scotfoot Well-Known Member

    Birch et al have done some very interesting work over the last year or two and a Phd thesis has now been summitted.

    I was a little surprised by the direction of travel of part of the abstract -"highlights an important energy-saving mechanism that may be incorporated into the design of footwear and assistive devices to restore and/or enhance normal function."

    No mention of strengthening the intrinsics to improve foot function : Perhaps that is to come in later papers.
    I am not convinced that shoes which are designed to reduce intrinsic work even more than modern shoes do is altogether a good idea since modern shoes already produce foot weakening.


    Optimising the spring in your step: analysing the neuromechanical adaptations of foot function to changes in surface

    Birch, JV
    Date: 21 November 2022
    http://hdl.handle.net/10871/131834
    Accepted version (PDF, 4.045Mb)
    Thesis or dissertation

    Chapter Six aimed to determine the role of the intrinsic muscles in generating mechanical work to replace that dissipated by a damped surface. Participants activated their intrinsic muscles more to perform more work on a damped surface, emphasising the important contribution of the foot in generating mechanical work. This thesis emphasises that appreciating foot function should be a fundamental consideration in understanding how humans control movement and highlights an important energy-saving mechanism that may be incorporated into the design of footwear and assistive devices to restore and/or enhance normal function.
     
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