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Variations in intrinsic foot musculature among hominoids

Discussion in 'General Issues and Discussion Forum' started by NewsBot, Jan 14, 2018.

  1. NewsBot

    NewsBot The Admin that posts the news.

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    Multivariate analysis of variations in intrinsic foot musculature among hominoids.
    Oishi M et al
    J Anat. 2018 Jan 12. doi: 10.1111/joa.12780.
     
  2. scotfoot

    scotfoot Active Member

    Looking only at the abstract of the paper above , I wonder if the authors have taken into consideration the arches of the human foot , absent in the other great apes , which make an enormous difference to the functional capabilities of the intrinsics . Size isn't everything .
     
  3. Rob Kidd

    Rob Kidd Well-Known Member

    I suggest you think from the other end. The apes all have a remarkable fine, tactile discrimination ability with their feet - almost analogous to the human hand. Thus one would expect huge differences in their collective intrinsic muscle morphology as compared to humans. Notwithstanding there are notables patterns of morphological variation both between apes as a group and humans, and between groups of hominoids. Let us not forget that withing the three essentiall ape groups, there is significant locomotory patterns, covering the whole spread of knuckle walking, to temprorary bipeds, to arboreal, including above branch plantigrady. The presence or absence of an arch, respect to this line of inquiry, is, in my opinion, a Furphy (as we say in Ozz).

    I have read the whole paper (I have library rights as a member of a university staff). I was particularly interested as they used principal components analysis - a multivariate tool that I have used extensively. They do not say whether they used the correlation or the covariance matrix as the basis for their analasis, and this make some difference as to the interpretation - much depends upon whether the standard deviation (ie variance) of the sample sub groups (there is only one group in PCA) is biologically meaningful. And sadly, they do not report fully upon the eignvalues and eignevectors of the individual prinicpal components - this would have been very interesting.

    With respect to your "size is not everything" remark, they did go to some extent to attempt to normalise for size before their mulitvariate analysis. Normalisation techniques are notorious for introducing false patterns in data. Notwithstanding: "To normalise the influence of body size, the mass of each muscle was divided by the total intrinsic muscle mass to calculate the mass fraction". They avoided allometric scaling (A=BXK [in this equation K is an exponent - I cannot type that inside this programme]) and body total mass scaling.

    There is always a tendency in quantitative studies to lose track of the biology. One should never forget the overriding maxim of "Biology, Form and Function". In this case that should be expanded to "form, function and phylogeny".

    Rob
     
  4. scotfoot

    scotfoot Active Member

    Hi Rob

    With regard to my Furphy ,maybe it is . My point ,which may be off topic relative to the paper under discussion , is that because the human foot has a dome like structure , the intrinsics can have a role in the human foot which they cannot have in the relatively flat feet of the other great apes . And that role is in keeping the tibia and hence the body balanced on the "talocalcaneal stack" both in standing and dynamic activities .

    Gerry
     
  5. scotfoot

    scotfoot Active Member

    With regard to the above Professor Chris Nester has just started his own blog site . In one of his articles he states -

    "The foot is only ever a pure mechanical structure when it is detached from the control system. Have you ever held a fresh cadaver foot? It’s quite difficult to make the foot stand normally or simulate ground contact in a way you would recognise as “gait”. It just flops about and is quite unwieldy. It is not what you see in clinic or when you take your shoes and socks off.
    The foot is therefore never a purely mechanical structure and it is always under some level of intelligent control."

    Exactly . The foot is designed to be unstable especially in the rearfoot area . Unstable that is until you add in the intrinsic and extrinsic musculature and neural control . Once you add these in to the equation , the narrow heel of the human foot makes balancing the body above easier . His blog site can be found here - talkingfeet.online/2018/01/04/why-am-i-blogging/ … via @ProfChrisNester
     
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