Fig. 6

Effect of perturbation force and exoskeleton controller on muscle activity. The exoskeleton controller type influenced the increase in soleus activity after push perturbations [F(2,22) = 5.2763, p = 0.013]. Soleus activity in the first 500 ms after perturbation onset was smaller for the neuromuscular controller with COM feedback compared to the default neuromuscular controller (p = 0.006) and compared to the minimal impedance controller (although not significant, p = 0.057) (A, B). The exoskeleton controller type also influenced the increase in tibialis anterior activity after pull perturbations [F(2,18) = 15.1174, p = 0.0001]. Tibialis anterior activity was smaller in the neuromuscular controller with COM feedback compared to the default neuromuscular controller (p < 0.001) and compared to the minimal impedance controller (p = 0.036) (C, D). A and C contain data of one representative subject. The bar plots in B and D contain data of all subjects with the dots representing the response of individual subjects and the bars the averages across subjects. A repeated measures anova with Tukey’s HSD post-hoc test was used to compare the pelvis displacement between controllers