STRUCTURE, MECHANICS AND INJURIES IN IDENTICAL TWIN RUNNERS: A CASE STUDY.:

1458 The purpose of this study was to compare the structure, mechanics and injury patterns of two 22 year-old identical twin male runners. Both subjects were competitive triathletes who typically ran 15 miles per week on average. Each had a history of bilateral pain along the medial borders of the tibiae, right fibular stress fractures and iliotibial band (ITB) syndrome. The subjects were previously given standard orthotics that did not alleviate their symptoms. Each was then given 25° inverted orthotics to which they responded well. Posturally, both subjects exhibited genuvarum, wide-based stance, and midfoot pronation. A structural assessment revealed mild rearfoot varum, forefoot varum, tibial varum and tight ITB in both subjects. The similarities in structure and injury patterns led to an investigation of their three-dimensional mechanics during running. Both subjects were forefoot strikers, exhibiting mechanics characteristic of this foot strike pattern. This pattern has been reported to be related to the anterior tibialis pain both runners experienced. Both subjects exhibited an excessive initial medial ground reaction force suggesting a laterally directed force which might place abnormal stresses on the fibula. Finally, because both subjects exhibited increased tibial internal rotation late into the stance phase, increased stress may have been placed on the ITB as the knee was attempting to extend. Additional studies of identical twins may lend further insight into the relationship between structure, mechanics and injury.