Lower Extremity Kinematic and Kinetic Adaptations During a Half Marathon

This study aimed to clarify the biomechanical adaptations recreational runners experience during a half marathon. Thirty-seven healthy runners completed a half marathon as fast as possible on a laboratory-instrumented treadmill. Kinematic and kinetic data were collected every 5 km from 0 to 20 km. As mileage accumulated, peak vertical ground reaction force (GRF) decreased from 5 km onward (p < 0.005) and impulse declined from 10 km (p < 0.05). Ground contact time increased from 10 km (p < 0.05). Joint-level adaptations included an increased hip extension moment (p < 0.005) and hip adduction angle from 10 km (p < 0.05), decreased knee abduction moment from 5 km (p < 0.005), and greater knee flexion angle at 10 km (p < 0.001) and 15 km (p = 0.031). Additionally, the symmetry angle of peak vertical GRF decreased at 20 km, suggesting improved interlimb symmetry under fatigue. These findings provide insight into fatigue-related biomechanical adaptations during long-distance running. Further research is needed to clarify how these changes relate to injury development.