Is leg stiffness joint angle specific? I've read that this is the case with isometric lifts and the two seem to be closely related – at least superficially.
What are the factors that influence leg stiffness? Tendon stiffness? Isometric/eccentric muscular strength?
Studies on the effect of surface on leg stiffness have shown that the body adjusts to running on softer surfaces by increasing joint stiffness – in light of this is there any room for grass training? I can think of a number of top groups that utilise grass for tempo and/or speed work, could this be a byproduct?