Juhani Takanen wrote:to back up that; do you have reasoning for that?
“Because of the natural physiology of the hoof capsule, we have to take into consideration the tolerance margins of expansion, contraction, compression and distortion. It is well documented that as the hoof capsule comes under weight loading it changes its configuration by
contraction of the heels,
expansion of the quarters and compression at the toe. We further have to consider the element of shearing forces as the horse turns and maneuvers its body mass over the foundation of the foot. " (Duckett)
"Frog pressure is not required for hoof expansion, and in some hoofs, increasing frog pressure without changing the hoof angle caused contraction, instead of expansion. "(Colles)
"According to Dollar, earlier experimenters Lechner, Gierth, and Dominik each measured contraction at the heels occurring naturally under weight bearing. Though a larger number, including Lungwitz, claimed to find expansion of the heels, Dollar, apparently unable to prove or disprove the conflicting reports, settled for the consensus, with some additional weight given to experiments with live hooves -- of which, Lungwitz did the greatest number."(Heymering)
"According to Dollar, Lungwitz' measurements of normal hoof motion were dependent upon "Flexibility of the horn, and a well developed but untrimmed frog." (Heymering)
"According to Reeks, in the absence of frog pressure Lungwitz found, "Contraction of the solar edge of the heels occurs at the moment of greatest over-extension of the fetlock joint -- that is, in a foot with pressure from below absent. On the face of it, this appears impossible. Lungwitz, however, has perfectly demonstrated it ... "is but a simple and natural result of foot dynamics. The movement of the plantar cushion will now be downwards, as well as backwards, and, seeing that it is attached to the inner aspect of each lateral cartilage, we shall expect these latter, by the downward movement of the plantar cushion, to be drawn inwards. This Lungwitz has shown to occur."(Heymering)
Logically, a plastic structure such as the frog, bordered on either side by the empty space of the lateral sulci would function so as to do everything but bear weight, or transmit pressure laterally.(Heymering)
"Consider what would result if the internal mechanisms of the hoof functioned to produce expansion. Because of its slope, the hoof wall by itself would expand during weight bearing -- the more weight and the more often it bore weight the more it would expand. If the internal structure increased that effect then one should expect to see collapsed or exploded hoofs from running or jumping. Clearly, the hoof must function to retain its integrity by counteracting external forces, not amplifying them. The action of the hoof with little or no frog pressure as described by Lungwitz should do just that -- internally producing contracting force simultaneously and in direct proportion to the external forces of expansion, or possibly slightly greater than the external forces of expansion, as that would result in a slightly more upright wall in the quarters, better able to withstand the load."(Heymering)
"Hunting (1941) largely accepted Lungwitz's conclusions but kept some reservations: '"the heels and quarters may be pressed together to some extent but they are prevented from being forced asunder by the fibrous connections of the frog-pad (plantar cushion) . . . expansion . . . may be practically disregarded in considering the best methods of shoeing sound feet." (Heymering)
There is more if needed.