The relationship between static postural measurements and biomechanical characteristics during landing

The purpose of this study was to examine the relationship between static postural measurements of the lower extremity and biomechanical characteristics during landing. Thirteen healthy and active subjects performed five trials of drop landing from three different heights (45, 60, and 75 cm) with two different landing techniques (soft and stiff). Standing static knee extension of the right side was measured in a screening session. Ground reaction forces (GRF) and right sagittal kinematic data were sampled simultaneously. Results were analyzed in a 3x3x2 repeated measures ANOVA using SPSS (SPSS Inc., Chicago, Illinois, USA) statistical software. Unilateral knee extension was significantly greater in Excessive Knee Extension Female (EKE-Fem) than either Male (ML) or Normal Knee Extension Female (NKE-Fem). As height and landing stiffness increased, results generally showed increases in the first (F1) and second (F2) peak GRF and the loading rate of F1 (LRF1) and F2 (LRF2) across all groups. Overall, NKE-Fem produced higher mean peak values for the selected vertical GRF variables regardless of height or landing technique. EKE-Fem generated lower F2 values than ML in the stiff landing at 75 cm and than NKE-Fem in F2, LRF1, and LRF2 in all landing conditions. A greater degree of plantarflexion and knee contact velocities were also observed in EKE-Fem during landing. These results suggested that an adaptive landing strategy was adopted by EKE-Fem to minimize impact forces. NKE-Fem landed with significantly greater knee extension angle and velocities at contact than ML at the two higher heights and greater F2, LRF1, and LRF2 than EKE-Fem in all conditions, indicating a poor capacity of the subject group in impact attenuation which could potentially overload the knee joint. In addition, the results suggest that while NKE-Fem might find difficulty in dissipating impact forces, EKE-Fem demonstrated a tendency to avoid full knee extension through compensatory measures at the ankle (increased ContAng and ROM). These findings demonstrate differences between males and females in kinetic and kinematic variables during landing, which may have implications in injury mechanisms of the anterior cruciate ligament.