Effect of the sagittal ankle angle at initial contact on energy dissipation in the lower extremity joints during a single-leg landing

During landing, the ankle angle at initial contact (IC) exhibits relatively wide individual variation compared to the knee and hip angles. However, little is known about the effect of different IC ankle angles on energy dissipation.The purpose of this study was to investigate the relationship between individual ankle angles at IC and energy dissipation in the lower extremity joints.Twenty-seven adults performed single-leg landings from a 0.3-m height. Kinetics and kinematics of the lower extremity joints were measured. The relationship between ankle angles at IC and negative work, range of motion, the time to peak ground reaction force, and peak loading rate were analyzed.The ankle angle at IC was positively correlated with ankle negative work (r = 0.80, R2 = 0.64, p < 0.001) and the contribution of the ankle to total (ankle, knee and hip joint) negative work (r = 0.84, R2 = 0.70, p < 0.001), but the ankle angle was negatively correlated with hip negative work (r = -0.46, R2 = 0.21, p = 0.01) and the contribution of the hip to total negative work (r = -0.61, R2 = 0.37, p < 0.001). The knee negative work and the contribution of the knee to total negative work were not correlated with the ankle angle at IC. The ankle angle at IC was positively correlated with total negative work (r = 0.50, R2 = 0.25, p < 0.01) and negatively correlated with the peak loading rate (r = -0.76, R2 = 0.57, p < 0.001).These results indicated that landing mechanics changed as the ankle angle at IC increased, such that the ankle energy dissipation increased and redistributed the energy dissipation in the ankle and hip joints. Further, these results suggest that increased ankle energy dissipation with a higher IC plantar flexion angle may be a potential landing technique for reducing the risk of injury to the anterior cruciate ligament and hip musculature.