Evaluation of dynamic postural control during single-leg landing tasks using initial impact force, landing leg stiffness and time to stabilisation.

Time to stabilisation (TTS) provides limited information to evaluate the dynamic postural control for individuals with functional ankle instability in single-leg landing task. More information is needed to understand TTS and evaluate the dynamic postural control better. The purpose is to develop a method estimating TTS, initial impact force (IIF) and landing leg stiffness (LLS) through fitting ground reaction force (GRF) decay in single leg landing with exponential vibration decay function (EVDF), and investigate effects of landing directions and GRF components on these parameters. Thirty-nine healthy participants were recruited. EVDF was used to fit GRF decays in different single-leg landings. TTS, IIF, and LLS were compared across landing directions and GRF components. The mean regression determinants of fitting GRF decays with EVDF were greater than 0.50. TTS was sensitive to GRF components (P = 0.041 females, P = 0.028 males). IIF was sensitive to GRF components (P = 0.001) for both genders. LLS was sensitive to GRF components (P = 0.023) for males. This method showed a moderate to strong feasibility for reporting GRF decay during landing, and provided movement characteristic information for better understanding of dynamic postural control together with TTS during landing.