Fig. 2

Experimental and simulated joint angle kinematics over gait cycle. a–c mean flexion and extension angles of ankle, knee, and hip joints over the gait cycle in percent for healthy controls (green), prodromal SPG4 (blue), and manifest SPG4 (red), with their standard deviation. Significant periods are indicated as lines above the trajectory plots indicating different levels of significance (thin line: \(p<0.05\), intermediate line: \(p<0.0056\), and bold line: \(p<0.001\). Differences between prodromal SPG4 vs. HC and manifest SPG4 vs. HC are shown as blue and red lines, respectively. d–f: flexion and extension angles of ankle, knee, and hip joints over the gait cycle in percent for different levels of velocity feedback gains (color coded from black: \(\omega _h=0\%\), light grey: \(\omega _h=93\%\)) of plantarflexor and dorsiflexor muscles. The extracted features are highlighted yellow, namely the minimum plantarflexion d and knee angle at heel strike (e)