Peak Impact Forces and Metabolic Cost During Mid-Forefoot Striking in Shod Versus Barefoot Runners

Inclusion Criteria: * trained runners with a running foot striking style of either initial forefoot or midfoot strike. * run on average at least 20 miles/week * be able to run for at least 20 minutes at one session * free of any orthopedic limitation Exclusion Criteria: * history of lower extremity injury within the last 6 months prior to testing * rear-foot strike running style * does not run in a cushioned shoe on any occasion * runs on average \< 20 miles/week * unable to run for 20 minutes or greater * presence of any open wound or deformity on the feet which would prevent participant from running barefoot * neurologic injury that would preclude normal running activity.