Substantial modifications in midsole geometry to vary rearfoot movement were used on trained subjects who performed 12.5 km runs with each shoe modification respectively (Kersting & Newman, 2003). Impact forces and rearfoot motion did not follow predicted values from previous studies (Stacoff et al., 1988). However, results showed large, but individually different variations in neuromuscular effort. No current literature has compared subtle changes in rearfoot kinematics to oxygen consumption and muscle activations during running. The purpose of the current study was to relate rearfoot movement during treadmill running in three systematically modulated heel inserts to oxygen consumption, mechanical parameters and muscular activity. Minimal inserts produced systematic alterations in rearfoot movement which did not result in substantial changes in RE or perceived exertion. However, changes in rearfoot eversion were linked to muscular activity which may be related to oversuse injuries in long lasting runs.
