Influence of heel height on ankle joint moments in running.

Clinically, heel lifting or heel wedging in running shoes has been proposed as a prevention and treatment of Achilles tendinitis. It has been speculated that heel lifting decreases the Achilles tendon forces. The purpose of this study was to determine the effect of heel height on resultant ankle flexion moments during running. It was assumed that plantarflexion moments at the ankle joint would indicate Achilles tendon loading. Each of the five subjects performed five running trials (4.6 m.s-1) for each of the five shoes, differing only in heel height (2.1-3.3 cm). Resultant plantar-/dorsiflexion moments were calculated using a standard three-dimensional inverse dynamics analysis. The results showed that, typically, a small initial dorsiflexion moment took place changing into a larger plantarflexion moment before 20% of stance phase. The magnitude and time of occurrence of the initial dorsiflexion moment were significantly affected by heel height changes, but the maximum plantarflexion moment and its time of occurrence were not significantly affected. The results did not support the speculation that a heel lift generally decreases the Achilles tendon loading during running. However, single subject analyses indicated that for two subjects the plantarflexion moments decreased with increasing heel height.