Fig. 2

Flowchart of the study set up. The support surface rotations were used in the experiments and simulation to perturb the proprioceptive information, resulting in 3 time series, the body sway (BS(t)), the torque (T(t)) and the muscle activation (MA(t)). Each time series was used to estimate the sensitivity functions resulting in 3 sensitivity functions, sensitivity to support surface rotation of the body sway (H(f)_SS,BS), of the torque (H(f)_SS,T) and of the muscle activation (H(f)_SS,_MA). All combinations of the sensitivity functions were used in model fits to obtain estimated parameters. Three models were fitted, 1) without activation dynamics, 2) with activation dynamics and 3) with activation dynamics and acceleration feedback. The resulting 12 parameter sets were used to investigate the accuracy and the reliability