Running is a popular activity that 9% of the U.S. population participates in at least once per week. There is a risk associated with running, as 37-65% of runners experience injury annually. Patellofemoral pain syndrome (PFPS), iliotibial band syndrome (ITBS), and tibial stress fractures (TSF) are three common injuries. Previous studies have identified relationships between loading parameters and these injuries. Core musculature, and its role in injury prevention, is a popular topic in the biomechanical community. However, few studies have focused on the core’s relation to knee injuries during running, specifically.

This thesis had three objectives:​ (1) to investigate how decreasing core activation during running would affect knee loading and lower extremity muscle activation;​ (2) to observe how different running kinematic styles were affected by decreased core activation, using representative subject specific motion capture data;​ and (3) to establish the feasibility of creating forward dynamic simulations of running to enable future simulation-based running research.

Representative running trials from six subjects, each representing a kinematic style of running (high and low normalized stride length, lumbar rotation range, and lumbar flexion/extension range) were simulated in OpenSim. Core muscle activation was constrained, and the effects on knee loading and lower extremity muscle activations were analyzed.

The average external rotation impulse acting on the tibia increased from 0.16 Nm*s to 0.19 Nm*s when core activation was decreased. Since external rotation of the femur relative to the tibia has been linked with PFPS and ITBS, this result suggests that decreased core activation may increase injury risk. Axial tibial force has been linked to TSF, and average axial force on the tibia increased from 4,947 N to 5,078 N when core activation was decreased, suggesting a link between reduced core activation and TSF. Swing leg muscle activation increased by 16.67% when core activation was decreased. Increased lower extremity muscle activation may cause faster fatigue, and increase injury risk. Hip abductor muscles averaged a 20.58% increase in activation, suggesting an increased risk of ITBS.

Analysis of different running styles demonstrated that tibial abduction angular impulse was seven times higher in the high stride length subject than the low stride length subject. Tibial abduction angular impulse has been identified as a contributing factor to PFPS, suggesting that running with a long stride length may increase injury risk.

Forward dynamic simulations of all six subjects were successfully generated. To our knowledge, this was the first time that forward dynamic simulations of running have been generated, and this work will enable future study of how kinematics and kinetics change as perturbations or muscle activation variations are applied.

Overall, these results provide targets for additional biomechanical investigation of the role of core musculature deficiencies in running injuries, and a new simulation tool for performing these investigations.