Energy dissipation during single-leg landing from three heights in individuals with and without chronic ankle instability.

Inadequate energy dissipation during landing may increase the risk of ankle sprain. Mechanical demands (landing height) in landing tasks may affect the biomechanical differences between individuals with and without chronic ankle instability (CAI). However, energy dissipation strategies during landing from various heights in individuals with CAI are unclear. The purpose of this study was to compare the effect of landing height on lower extremity biomechanics between individuals with and without CAI. Eleven participants in each of the CAI and Control group performed a single-leg landing from three heights (30, 40, and 50 cm). We calculated the contribution of each joint to total energy dissipation at 50-ms intervals during 0-200 ms post-initial contact (IC). Peak joint angles and moments and joint stiffnesses were calculated during 0-200 ms post-IC. Two-way mixed analysis of variance revealed significant group-by-height interactions for hip energy dissipation at 101-150 ms post-IC and peak ankle plantarflexion and hip extension moment. These significant interactions suggested that the effects of landing height on the ankle and hip joints differ between individuals with and without CAI. The effect of mechanical demands on altered landing biomechanics among CAI populations should be considered in biomechanical studies and clinical practice.