EMG activity with and without feedback. a: Mean group PSDs of BVL EMG activity with and without feedback compared to mean activity of controls without feedback for the task of standing eyes closed on foam. The upper grey line is mean BVL activity without feedback, the lower black line is the mean activity with feedback. Triangles indicate those frequency bins where the PSD values were significantly lower with feedback (p < 0.05). The grey dotted lines indicate the mean of healthy control values (without feedback). The mean values of BVL subjects with feedback were not significantly different from controls, except for tibialis anterior. b: Mean group activation ratios of pairs of ankle (tibialis/soleus) and trunk (paraspinals/obliques) muscles compared for BVL subjects with and without feedback and to controls. The ratios at each frequency are of PSD values shown at the same frequency in a. For example, the tibilalis anterior/soleus ratio for BVLs at 1.9 Hz is the ratio of the PSD values of the thick lines in A for tibialis and soleus. The vertical bars mark the 95% confidence intervals. Asterisks (*) mark significant (p < 0.05) differences of BVL subjects with and without feedback, while gate symbols (#) mark trends (p < 0.1).