Altered Joint Powers During Running After Tibial Bone Stress Injury

Background: Tibial bone stress injuries (tib-BSI) are common in adolescent runners. Previous research has examined running mechanics as possible risk factors for tib-BSI’s and implications have been observed for both kinematic and kinetic measures. Combining these measures to examine power absorption and production of the lower extremity can provide context on mechanical differences in individuals with a history of tib-BSI. Hypothesis/Purpose: The purpose of this study was to examine total limb power and percent joint contribution in healthy adolescent runners compared to peers with a history of tib-BSI. It was hypothesized that runners with a history of tib-BSI would have a greater contribution of power production and absorption at the ankle, and less at the hip and knee joints, with no difference in total power. Methods: Twenty-six runners were divided into groups: history of tib-BSI (n=14; male=10, female=4; age=16±2) and healthy controls (n=12; male=5, female=7; age=18±7). Data were collected using 3D motion capture with embedded force plates during overground running at self-selected pace. Total limb power and percent joint contribution were calculated from joint work. Positive and negative joint work was summed from the integrations of the joint power-time curve in each plane. Joint work was divided by step-time to obtain total joint power. Joint powers for the hip, knee, and ankle were summed to determine total limb power and percentage of limb power was calculated for each joint. Variables were grouped by control limb (CON), uninvolved limb (UNI), and involved limb (BSI). Both limbs in the healthy controls were averaged to generate the CON group. A one-way ANOVA was used to compare the variables of limb and joint power. Results: There were no significant differences between BSI and UNI limbs for any variables measured. The CON group exhibited significantly greater hip negative power compared to the BSI group (p=0.047), and significantly less ankle negative power compared to the BSI (p=0.001) and UNI groups (p=0.002). Despite a significant difference in total positive power between groups (p=0.04), there were no differences in joint positive power. Variables are presented in Table 1. Conclusion: This study is preliminary evidence that adolescent runners with a history of tib-BSI can present with adaptations in running mechanics that are not limited to the injured leg. Negative power may be more sensitive to change with the ankle increasing its contribution, comparatively. Clinicians and researchers should be aware of this adaptation after injury as it may influence treatment.