Bi-directional Bi-directional long short-term memory Biophysics Brain Center of gravity Cost effectiveness Cost engineering Costs Daily lives Feature engineerings Forecasting Gait analysis Gait phase classifications Gravitation Insole system Learning algorithms Long short-term memory Machine-learning Mean square error Performance Prediction modelling Semantics Trajectories balance bi-directional long short-term memory center of gravity feature engineering gait analysis gait phase classification insole system