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Toe curls are not an affective way of strengthening the intrinsic foot muscles

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Dec 18, 2019.

  1. scotfoot

    scotfoot Well-Known Member

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    Researchers at Brigham Young University have just published a paper (see below ) which demonstrates why toe curls are not an effective exercise for strengthening the abductor halluces in the foot . The exercise produces only relatively low level of activity in this muscle and in my opinion relies instead on the extrinsic toe flexors .

    Doming exercise against resistance produced near maximum activity in the abductor halluces according to the information in the paper .

    Note ; I own Jomarg Innovation a company with interests in this area .

    Functional assessments of foot strength: a comparative and ...

    https://bmcmusculoskeletdisord.biomedcentral.com › articles

    1. Cached
    3 days ago - In particular, the intrinsic foot muscles contribute to many of the same actions as larger extrinsic lower limb muscles, making it difficult to isolate their effects
    Last edited: Dec 18, 2019
  2. scotfoot

    scotfoot Well-Known Member

    Dear Admin
    I have added the content of this thread to another " Toe curls .What do they achieve " so this one can be deleted if you like .
  3. Dr Rich Blake

    Dr Rich Blake Active Member

    I have discouraged my patients from doing toe curls in favor of metatarsal doming or arcing for years. Rich
  4. scotfoot

    scotfoot Well-Known Member

    Hi Rich ,
    I believe you are perfectly correct to go with metatarsal doming rather than toe curls and the study just produced by Brigham Young University backs that up .

    To summarise the study , a group of researchers looked at the amount of electrical activity (EMG) produced in a number of muscles during toe strength measurements using 3 basic measuring methods . The electrical activity was used as a surrogate for muscle engagement during the exercises .

    Methods one and two were respectively (1) toe curls using a special piece of equipment , and (2) the very simple approach of standing on a pressure mat and pushing the toes of one foot downwards . The second method produced a peak EMG in the abductor hallucis of about twice that found in toe curls indicating that it would probably be a far more effective method of strengthening the foot intrinsics .

    In fact ,although the researchers went out of their way to get a toe curl device that would produce as high an amount of activity in the abductor hallucis as possible , it remained only at about 30% of the maximum 100% value used by the researchers . So toe curls , flat out and in the optimal conditions , are probably of very little use , if any , in strengthening the abductor hallucis or other intrinsics .

    I realise that some influential academics have , in the past , advocated the use of all sorts of toe curl activities and devices , but this study indicates just how inappropriate these are for foot strengthening . In my opinion you might as well be trying to improve bicep strength by simply swing your arms backwards and forwards .

    And so to the third measurement method the researchers used . This method was in a different category altogether than (1) and (2) .

    Method (3) used metatarsal doming but with an inelastic plastic cuff placed over the dorsal surface of the foot to resists the doming action . The EMG in the abductor hallucis produced by this method was near 100 % of the experiment maximum value .
    Actually , a better way of isolating the abductor hallucis during this "isometric hold "measurement method , is to have the toes raised in a dorsiflexed postion . This method has already be used by other research groups to build foot strength by up to 60-70% in only 8 weeks .

    It is also worth noting that method (3) used by the researchers also produced EMGs in the tibialis anterior and peroneus longus that would indicate muscle strengthening would occur in these muscles if the protocol was switched from measuring to strengthening . So potentially one simple exercise , lots of muscles around the foot and ankle strengthened .

    Last edited: Dec 22, 2019
  5. Dr Rich Blake

    Dr Rich Blake Active Member

    Gerry, thank you so very much for the explanation! Toe curls have especially bothered me with the pes cavus people as it encourages hammertoes. Have you heard of Toe Pro device for intrinsic muscle strength? Just heard of it at a lecture in New York. Rich
  6. scotfoot

    scotfoot Well-Known Member

    I realise of course , that you are perfectly capable of reading and understanding the paper for yourself , but I thought I would summarise it for any other readers who might be disinclined to visit the paper via the link.

    Re the Toe Pro , yes I am aware of it and I think it is soon to be tested on patients in the USA .

    One other thing that might be of interest to you is a conference abstract (see below ) that looks into intrinsic and extrinsic foot muscle involvement in posture .If you look at figure 1 , you can see that in a double squat position , the most active foot muscle by far is the tibialis anterior (35% of MVC ) .

    You can see then why older people , with age induced muscle atrophy , might have trouble getting into and out of chairs , since this involves the double leg squat position ,which might be difficult with weakened tibialis anterior muscles .

    Intrinsic and extrinsic foot muscles have unique roles in ...

    www.asbweb.org › conferences › abstracts › 313AE--Intrinsic And Extrins...

    by T Kurihara - ‎Related articlesOur results indicate the intrinsic and extrinsic foot muscles activate as unique groups. The activity of intrinsic and extrinsic foot muscles increases with postures of increasing balance difficulty in a similar manner.
  7. Dr Rich Blake

    Dr Rich Blake Active Member

    Plus as they age the Achilles tightens making it harder for the AT to work. Rich
  8. richardbaker

    richardbaker Welcome New Poster

    Toe curls have especially bothered me with the pes cavus people as it encourages hammertoes. Have you heard of Toe Pro device for intrinsic muscle strength? Just heard of it at a lecture in New York. Rich
  9. scotfoot

    scotfoot Well-Known Member

    Generally speaking , until now , just about every site on the internet offering advice on exercises for the foot has included toe curling activities , such as the towel curl , as part of its information package . This includes sites run by national and respected professional bodies .

    I , and many others , think it is a bad exercise since it targets the extrinsic toe flexors , not the intrinsic toe flexors , and may have the capacity to cause or exacerbate muscle imbalance .

    Yesterday , for the first time , I came across a Scottish NHS site which gives advice on foot exercises but which does not include any reference to toe gripping exercises . I have no idea who was advising them (the site organisers ) but it appears to have been a person or persons who know their onions .

    www.nhsinform.scot › muscle-bone-and-joints › exercises-for-foot-pr...
    Exercises for foot muscle or joint problems | NHS inform

    26 Aug 2019 - Exercises for foot problems. Introduction. Seated foot and heel raise. Toebend. Big toe lift and hold. Standing calf stretch. Ankle stretch.
  10. scotfoot

    scotfoot Well-Known Member

    Adapted from ; Bruening, D.A., Ridge, S.T., Jacobs, J.L. et al. Functional assessments of foot strength: a comparative and repeatability study. BMC Musculoskelet Disord 20,608 (2019). https://doi.org/10.1186/s12891-019-2981-6

    In my opinion these pictures and graphs , taken from the paper referenced above , demonstrate why toe curls are a near useless exercise for strengthening the intrinsic foot muscles .
    Fig A shows a max toe pull or curl , and you can see in muscle activation graph linked to by the red arrow , that the abductor hallucis is not that active in the exercise .
    Now look at the activation levels linked to exercise C , where the toes and muscles of the lower leg arch the top of the foot up against a fixed nonelastic leather strap . Far higher activation levels .

  11. scotfoot

    scotfoot Well-Known Member

    The authors of the research mentioned in the post above have produced a new paper (see below) on diabetic neuropathy and the intrinsic / extrinsic foot muscles . To measure strength they have quite rightly dropped the toe curling measuring method and focused instead on a simple toe press figure B above and foot doming, figure C .

    I would suggest that the results from the doming exercise method would be far more accurate if they moved the measurement system to under the toes ( a pressure mat or the like ) and merely had an inflexible leather band across the top of the foot to hold it in place and provide resistance to upward movement of the foot .
    This would greatly simplify the instruction to the patient which would become simply " press down with your toes as hard as you can against the mat " . The measurement could be taken seated and with the ankle in a plantar flexed position to reduce the input of the extrinsic toe flexors .

    Measuring pressure/force generated across the top of the foot involves many more muscles than just the intrinsic/extrinsic toe flexors and would give poorer results than the under toe measurement option .

    Early-Stage Diabetic Neuropathy Reduces Foot Strength and ...

    search.ebscohost.com › login
    search.ebscohost.com › login
    by AD Henderson - ‎20207 days ago - To evaluate individual intrinsic and extrinsic foot muscle sizes and functional foot ... Sizes of 10 separate muscles of the lower leg and foot were measured using ...
  12. scotfoot

    scotfoot Well-Known Member

    Re the post above , this type of rig is more appropriate for measuring toe flexor strength see fig B . Ideally, the ankle should also be in a plantar flexed position .

  13. scotfoot

    scotfoot Well-Known Member

    Below is a link to a poster presentation of work which looked at the link between intrinsic foot muscle strength and dynamic balance in an older population .
    No link was found , which in my opinion is not surprising since the measurement methods used are not suitable for measuring intrinsic muscle strength .

    Referring to post #10 above , the present authors used methods A and C to measure intrinsic strength and for some inexplicable reason not method B .

    Using toe curling (gripping ) to measure intrinsic muscle strength ( or strengthen these muscles ) is a nonsense , since the level of intrinsic activity produced by these methods is so low compared to the much greater input of the extrinsic toe flexors . ( Actually , in my opinion , the poster presentation demonstrates that there is no correlation between extrinsic toe flexor strength and dynamic balance and has nothing to do with the intrinsics . )

    With regard to measurement method C , many muscles are involved in doming ,the weakest of which are the intrinsics. As presented , the method is a hopeless way of measuring intrinsic strength since this should be recorded under the toes .

    They had 3 methods ,one works and they went with the two that wouldn't . Go figure !

    "Comparing Intrinsic Foot Muscle Strength and Dynamic ...

    scholarsarchive.byu.edu › library_studentposters_2020
    scholarsarchive.byu.edu › library_studentposters_2020
    1. Cached
    5 days ago - BYU ScholarsArchive Citation. Graham, Aubree; Bruening, Dustin PhD; Johnson, A. Wayne PT, PhD; and Ridge, Sarah PhD, "Comparing Intrinsic Foot Muscle ...
    Last edited: Apr 8, 2020
  14. scotfoot

    scotfoot Well-Known Member

    An interesting development from the University of Sydney is the filing of a patent application for a foot strengthening/ training device ,( link at bottom of this post ).

    The paper describing the device includes Joshua Burns , a researcher of international renown, amongst its authors , and includes photographs in figure 2 which demonstrate that the researchers understand that to "dome "the foot in a way that engages the intrinsics ,the metatarsophalangeal joints or ball of the foot, must be raised clear of the ground .

    Fig 2 images


  15. scotfoot

    scotfoot Well-Known Member

    Here is an abridged diagram that directly illustrates the difference in activation levels of the muscles of the foot when foot doming and toe curls (with maximum effort ) ,are compared .
    You can see that for the abductor hallucis, the doming exercise produces almost 3x as much activity in this muscle than toe curls .

    The toe curl part of the graph shown is for max effort with the hallux which IMO is much more about the FHL than the intrinsics . Thus, toe curls against increasing resistance may well strengthen the long toe flexors but not the intrinsics .

    Again IMO , the possibility of introducing or worsening muscles imbalances with the toe curl exercise , is real .


    Graph abridged from
    Bruening, D.A., Ridge, S.T., Jacobs, J.L. et al. Functional assessments of foot strength: a comparative and repeatability study. BMC Musculoskelet Disord 20, 608 (2019). https://doi.org/10.1186/s12891-019-2981-6
    Last edited: May 16, 2021

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