Fig. 4

Gait features over disease severity and simulated dysfunctional neuro-muscular mechanisms. a Minimum plantarflexion and b knee angle at heel strike of experimental data and simulations over disease severity (SPRS score) and velocity feedback gain \(\omega _h\), muscle weakness \(\omega _w\), and velocity feedback gain and muscle weakness \(\omega _{hw}\). The three experimental groups are color-coded with healthy controls (green), prodromal SPG4 (blue), and manifest SPG4 (red). Shown are averaged values for SPRS scores as blue and red circles. Error bars are showing distributions of all groups with their mean SPRS score (position on lower x-axis) and standard deviation of SPRS score indicated by horizontal error bars. Orange, light blue, and purple squares are showing simulation data at different gains of velocity feedback (\(\omega _h\)), muscle weakness (\(\omega _w\)), and velocity feedback gain and muscle weakness (\(\omega _{hw}\)), respectively (upper x-axis). Quadratic fits for simulations are shown in the respective color