According to one embodiment of the present invention, the system for clinical assessment of movement disorders (iTUG) is comprised of a) a protocol to assess gait, balance, and mobility; b) a plurality of wearable sensors including accelerometers, gyroscopes, magnetometers, optical sensors, and goniometers to record kinematics data obtained from a patient during said protocol; c) means for wirelessly transmitting said kinematics data to a storage and data processing server; and d) a plurality of statistical and biomedical signal processing methods to analyze said kinematic data and derive a plurality of metrics (outcomes) to objectively quantify movement disorders. A specially important outcome for the assessment of movement disorders is described, namely, the quantification of the onset and offset parameters during turning. A method for quantification of said onset and offset turning parameters involves 1) collecting data to measure the angle of the trunk during turning, 2) modeling said angle using a mathematical model, and 3) using numerical optimization and estimation methods for fitting the model in the data to determine said onset and offset turning parameters.