The Influence of Prolonged Running and Footwear on Lower Extremity Joint Stiffness.

Supplemental digital content is available in the text. Introduction: The purpose of this study was to compare leg, sagittal plane knee and ankle, and frontal plane ankle stiffness over the course of a prolonged treadmill run in neutral and stability footwear. Methods: Thirteen male habitual rearfoot runners completed two biomechanical testing sessions in which they ran for 21 min at their preferred running speed in a neutral shoe, then changed either into the same neutral shoe or a stability shoe and ran a further 21 min on a force-instrumented treadmill. Three-dimensional kinematics and kinetics were recorded at the beginning and end of each 21-min interval. Results: No differences were observed in leg stiffness between footwear conditions throughout the run (P > 0.05). Knee stiffness increased during the first 21 min (P = 0.009), whereas ankle stiffness reduced at minute 21 (P = 0.004) and minute 44 (P = 0.006). These changes were modulated by an increase in ankle joint compliance and knee joint moments. No differences were observed between footwear conditions for leg and sagittal plane lower extremity joint stiffness (P > 0.05). During the second half of the run, frontal plane ankle stiffness increased in the stability shoe but decreased in the neutral shoe (P = 0.019), attributed to reduced eversion range of motion caused by the added medial post. Conclusions: These results suggest that over the course of a prolonged treadmill run, shock attenuation strategies change, which may affect the knee joint. [ABSTRACT FROM AUTHOR]