897 FO48 – Stress fracture injury prevention strategies with emphasis on early impact dampening among endurance runners

Background The relationships between time-dependent impact loading patterns and running-related stress fractures remains unclear, but our recent clinical findings suggest that controlling very early impact dampening after foot strike could lessen injury risk. Objectives To determine: 1) Differences in time-dependent impact loading patterns among runners with history of leg/foot stress fractures compared to non-injured runners, and 2) Whether a gait modification intervention attenuates early impact loading. Design Mixed method design, cross-sectional and intervention. Participants Male and female runners (n=300; 35±15yr, 22.5±3.3 kg/m2, 50.7% female) stratified into groups by stress fracture history: non-injured and history of leg and foot stress fracture (SFx) and an intervention group of healthy runners (n=8). Intervention Gait modification: 1-hr gait analysis session with video biofeedback of running form, and verbal cueing focused on optimizing leg/core muscle preactivation at foot strike. Main Outcome Measurements Time-dependent net ground reaction forces (GRF); medial-lateral GRF patterns during stance. Intervention outcomes included positive/negative loading oscillations, average impact loading rate. Results Cross sectional: SFx demonstrated greater net GRF during first 8% of stance phase on both limbs (p<.05), and greater medal-lateral GRF during the first 7–16% of stance phase (p<.05) than non-injured runners, suggesting the very early stance is an opportune time window to modify biomechanics. Intervention: Gait modification reduced early unloading after foot strike before full body load (up to the first 12% of stance; p<.05), dampened mechanical oscillation frequency, and reduced load rates by an average of 35.3 BW/s. Interlimb asymmetries in impact load rate were reduced by 7.9% from pre-post gai modification. Conclusion There is potential to lower risk for running-related stress fractures through gait modification techniques that control impact during early stance and dampen vibration.