The footpads of mammals maintain functional integrity as body mass increases through changes in geometry and material properties.

“In most mammals, footpads are what first strike ground with each stride.
Their mechanical properties therefore inevitably
affect functioning of the legs; yet interspecific
studies of the scaling of locomotor mechanics have all but neglected the
feet and their soft tissues. Here we determine how
contact area and stiffness of footpads in digitigrade carnivorans scale
with body mass in order to show how footpads’
mechanical properties and size covary to maintain their functional
integrity.
As body mass increases across several orders of
magnitude, we find the following: (i) foot contact area does not keep
pace
with increasing body mass; therefore pressure
increases, placing footpad tissue of larger animals potentially at
greater risk
of damage; (ii) but stiffness of the pads also
increases, so the tissues of larger animals must experience less strain;
and
(iii) total energy stored in hindpads increases
slightly more than that in the forepads, allowing additional elastic
energy
to be returned for greater propulsive efficiency.
Moreover, pad stiffness appears to be tuned across the size range to
maintain
loading regimes in the limbs that are favourable
for long-bone remodelling. Thus, the structural properties of footpads,
unlike
other biological support-structures, scale
interspecifically through changes in both geometry and material
properties, rather
than geometric proportions alone, and do so with
consequences for both maintenance and operation of other components of
the
locomotor system” (Chi & Roth 2010)

http://rsif.royalsocietypublishing.org/content/early/2010/02/23/rsif.2009.0556.abstract
http://www.dukenews.duke.edu/2010/02/footpads.html

Last Updated August 18, 2016