Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

What are toenails for ? Answer . Grip

Discussion in 'Biomechanics, Sports and Foot orthoses' started by scotfoot, Aug 8, 2016.

  1. scotfoot

    scotfoot Active Member

    Members do not see these Ads. Sign Up.
    So what function do our toenails serve ?

    Well I believe they have a number of roles to play but, in my opinion , chief among these is found in the way the unshod human foot interacts with a substrate to provided grip ,traction and balance .

    Toes have a pedunculated shape and when they are pressed into the ground the nail ( which is attached via the nail bed and associated ligaments to the periostium of the underlying phalanx) helps to cause lateral rather than vertical displacement of the toe pulp and hence a more even pressure distribution within the pulp and across the area of toe contact with the ground .

    The lateral displacement also helps the distal portion of the toe to take on a flattened ,bulb like configuration which helps to prevent the foot slipping during locomotion in yielding substrates such as wet soil .
    (Its much harder to draw a spoon through cold butter that a knife ) .

    Grip is further facilitated by the pressing of the forefoot into the ground during late stance which results in a mound of material being left in the sulcus area .

    It can be inferred from the above that perhaps the unshod foot grips best when the toes remain straight and flex only at the metatarsophalangeal joints since curling or clawing the toes will only lead to the extrusion of the substrate from between the toes themselves and from between the toes and the ball of the foot .

    Any thoughts ?


    Gerrard Farrell

  2. davidh

    davidh Podiatry Arena Veteran

    Hi Gerry,

    This is only a theory. It's a nice theory, and it may be correct, or partially correct, but without some science to show how, why, and if it is correct it remains a theory.

    Do some work on it, get it published, then argue your corner - is my advice.


  3. efuller

    efuller MVP

    An alternative. Toenails are a remnant from a long ago ancestor who had claws that were needed to fight to survive. As the use for tools developed there was less of a need for claws and smaller claws were selected for. However, any mutation that would make nails go away altogether would mean that we would loose fingernails too. That would not be adaptive because we would have a hard time pulling splinters from our fingers, or toes. We would also have a harder time opening pill boxes or picking up coins off of the street.

    I will concede that there might be a small selective advantage to the pads of the toes increasing grip. But toe grip is such a small advantage in the large scheme of things. It's hard to see there would be much selection pressure toward toenails that conferred a slightly better grip. It's not like a bunch of finches blown to a new island where the best food in their niche is hard seeds. A stouter beak would be much more important to survival in that case.

    It is fun to sit and think about things. :drinks

  4. scotfoot

    scotfoot Active Member

    Thank you for the comments .

    Unfortunately ,I am in a position only to talk the talk and walking the walk will have to be left to others ( over a yielding substrate ,in their bare feet and with due care and attention to proper scientific procedure ) .


  5. Rob Kidd

    Rob Kidd Well-Known Member

    I have to say that I think that toe nails (certainly not finger nails) are a vestigial structure; that is, they have no function, and have not had since our hominoid ancestors gave up the fine tactile discriminatory use of feet in exchange for the bipedal habit. This will have taken place at about the same time as the lumbrical/interossei changed morphology to that we have today. That is, the realignment of the foot from a third ray midline to a second ray midline. Let us not forget that digit nails are in fact modified claws. Rob
  6. davidh

    davidh Podiatry Arena Veteran

    I think Rob is right.


    I hope you don't mind me asking - why can't you write up your hypothesis and do some work on it?
  7. scotfoot

    scotfoot Active Member

    Rob ,
    Are you saying then that when the hallux is pressed into the ground the pattern of tissue displacement in the distal part of the toe will be the same whether a toenail is present or not ?

    I feel that when considering the toenails function it should not be viewed in isolation but with regard to the surrounding tissues and its influence upon them .

    In my opinion the pedunculated shape of toes gives a clear indication about one of their major functions ,grip

    Also ,surely the counter pressure ,propriosensitive mechanisms present in the fingers would also be useful in the toes all be it perhaps set at greater stimulus levels than the fingers .

    David ,
    Without meaning any offence whatsoever I feel that the validity of the hypothesis is self evident .

  8. davidh

    davidh Podiatry Arena Veteran

    No offence taken.

    I, however, feel that the validity of the hypothesis is not self-evident.

    This is why you need some proof, working-out, or at least a little more than an argument based on theories which you think are self-evident.


  9. Interesting study- pressure analysis pre and post total nail avulsion.:cool: You could just use a Harris-Beath mat and measure contact area...
  10. Rob Kidd

    Rob Kidd Well-Known Member

    I have no idea Gerry. however, anecdotally I can say that, given time to heal, of the many TNA patients that have been through the various schools I have worked at, I am not aware of any that have noticed any change of function. Rob
  11. davidh

    davidh Podiatry Arena Veteran

    What are toenails for? Answer - painting, if you're a girly. :D
  12. W J Liggins

    W J Liggins Well-Known Member

    Now that is self evident. However, it is also extremely sexist - what we boys do in our spare time is our business!

  13. scotfoot

    scotfoot Active Member

    Actually I am surprised that advocates of bare foot running and those who study the subject haven't looked into the how the unsod foot interacts with the ground to provide grip and traction . Its where i would have started .

    Anyway one final thought on this and its back to rugby boots and ,to make things topical ,Usain Bolt .

    So we have Mr Bolt playing rugby on a muddy pitch thundering down the wing . His boots have ten studs each and he is uncatchable .

    Half time sees him switch to boots with only one big stud each . Now when he tries to propel his body forward his single studed boot ,having only a single point of effective contact with the ground , allows his foot to rotate about the said stud .

    This rotation is repeated with each stride causing a dramatic loss of forward propulsion and , much to his embarassment ,he is caught and flattended by a chasing 20st prop .

    Similarly with a fleeing ,unshod ,early homosapien a single point of forefoot contact with the ground will lead to less effective locomotion ,failure to reach the sanctuary of the tree and involuntary consumption by a persuing carnivore .

    Muliple point of contact provided by the pads of the extended toes and the ball of the foot would solve the problem as I am sure it has done for many creatures through many millions of years .

  14. W J Liggins

    W J Liggins Well-Known Member

    Again, a nice hypothesis. However, you really need to develop the null hypothesis (easy) and then work to prove it (difficult). A good couple - or many more - papers.

    All the best

    Bill Liggins
  15. scotfoot

    scotfoot Active Member

    Hi Bill
    Some time ago ,in response to an email I sent him , Prof Dan Lieberman very kindly forwarded me a PDF of a paper on the mechanics of walking and running and toe length .

    The authors assumed that the toes stayed straight during function flexing only around the MTFJ .

    In my opinion ,for what that's worth in the present context , they were correct to make that assumption.

    It follows then that although toes grip they don't grasp and so the foot has multiple points of contact with the ground in late stance .


    The paper is -

    Walking, running and the evolution of short toes in humans
    Campbell Rolian1,*,?, Daniel E. Lieberman1, Joseph Hamill2, John W. Scott3 and William Werbel1
  16. scotfoot

    scotfoot Active Member

    Hi Bill
    Just a last bit on this .
    I thought I would reduce the problem to more general terms and post it on physics forum .

    For whatever reason nobody has responded on that site .

    The two posts I placed were as follows --

    This is a question about friction and grip .
    The set up is as follows ,-

    We have a non yielding ,consistent surface (x) fixed to a work bench .

    Next we have a removable lever arm made of a non flexible material and about 75 cm long .

    Fixed to the underside of one end of the lever arm we have a a non flexible plate which has an under surface made of rubber .

    The plate is circular , has a hole at its center and has a surface area of 100 cm sq. The lever arm itself does not touch the material x .

    Next ,via a bolt placed through the hole in the center of the plate and through the non yielding material we pivot-ably secure the lever arm to surface x so that the rubber lies on top of the surface x .

    The lever arm extends beyond the work bench and a force of 100 newtons is vertically applied to the plate so that the rubber is pressed against the surface x with a constant force .

    When the lever arm is moved the rubber covered plate rotates about the bolt axis in a rotational fashion and a given force ,F1 , is required to keep the lever arm moving .
    That's the set up .

    The question is as follows -

    A portion of the rubber covered plate,20cm sq is removed by making a cut across the plate at right angles to the lever arm and this is reattached to the system by a lever arm extension so that the cut surfaces of the two sections of the original plate are parallel and 5 cm apart . (that is the rubber plate is now in two sections the first as it was and rotating about the bolt and the second section now at a greater distance from the pivot point .

    The question -would greater force be required to get the lever arm moving against inertial frictional forces in this new system than in the original set up and would greater force be required to keep the system moving ?

    Thanks Gerry

    2nd post on physics site #2 Gerryf
    If it helps in the understanding of the problem here is the context .

    The plate represents the area in of the foot in contact with the ground after the heel leaves the ground . The whole plate represents the ball of the foot the toes in a curled position and the split plate represents a situation where the toes are extended .

    The question is --
    Does the planted foot resist rotation and slipping more with the toes curled or extended and to the best of my knowledge has not been asked or answered until now ?
    . Gerry

    I believe the answer to the above posts is that even on firm ground extended toes provide grip by providing multiple points of contact and a friction providing component further away from the pivot point than curled toes would .



Share This Page