I watched this come by and decided to say nothing until the world had read it, not the least because Jerry is a mate of mine; no one took the bait so I guess I will now jump in. I know that 30 years ago we put much greater stock in Elftman's midtarsal restraining mechanism than perhaps we should. However, one cannot doubt its existence, at least on the simple level of a subtalar supinated foot having a lesser ROM than a subtalar pronated one. Maybe the mistake was to attempt to put some variety of linear function to it in terms of degrees of change........... The extreme talar head torsion found in Homo sapiens but not Homo habilis (upon the basis of available specimens) goes some way to explain this - classic peramorphic heterochrony - taking the ancestral form and accelerating it even further (sort of the opposite of neoteny). Likewise, on the lateral side, the process calcaneus is a uniquely hominid feature, not present in any other primate and present in hominids since at least Homo habilis. It is a major feature in calcaneo-cuboid joint reduction in ROM. As Jerry et al rightly point out, midtarsal break as a normal event for them, not for us. Certainly it is true that humans with a midtarsal break are ligamentously lax, it may be true that their process calcaneus is reduced in magnitude, but if so, is this cause or effect? I do not know.
There is a tendency in science to throw babies out with the bathwater, and then come back looking them, so to speak; maybe we should come back and look for Elftman, but with the benefit of hindsight.
In addition, in this study, only light manual loads were applied to the forefoot, orders of magnitude below the amount of force that would be applied across the midtarsal joint during normal walking or running activities.
I don't see how this study tells us anything useful since it is, basically, a non-weightbearing study with no attempt to even record the forces used to push on the forefoot!
We are in Salford this Thursday, Northampton the Wednesday after that, and Plymouth on Friday 10th Oct. If you can drag your self to one of those venues - you can have the beer and a meal!
Well I guess it tells us that when we examine the foot non-weightbearing and see how inversion of the rearfoot reduces the amount of motion of the forefoot relative to the rearfoot, it probably isn't due to a reduction in the range of motion at the TNJ nor CCJ and said reduction is more likely to be occurring in the the other midfoot joints.
Midtarsal break variation in modern humans: Functional causes, skeletal correlates, and paleontological implications.
DeSilva JM, Bonne-Annee R, Swanson Z, Gill CM, Sobel M, Uy J, Gill SV. Am J Phys Anthropol. 2015 Jan 16. doi: 10.1002/ajpa.22699
Glad to see that my mate Jerry is busy and active. It is interesting how the palaeo foot, both recent and ancient, is becoming a serious research interest outside the podiatric world.