FIGURE 7.

User’s summed ankle muscle activity versus metabolic rate. Measurements of users’ summed normalized electromyography (EMG) signals recorded from soleus + medial gastrocnemius + lateral gastrocnemius + tibialis anterior (SOL+MG+LG+TA) over a stride from heel strike (0%) to heel strike (100%) of the same leg are shown (A,B). Bar graphs are averages of the summed EMG signals over the stride (C,D). All measurements are averages across the study participants (N = 9) in each condition with varying neuromuscular model (NMM) controller reflex Gain (green) in left panel (A,C) and Delay (blue) in the right panel (B,D). Linear regression between the change in metabolic rate versus the change in average summed EMG with respect to the unpowered (NoPwr) condition (E). * denotes pairwise significant difference of p < 0.05. R² value is denoted with a “∼” if the linear regression was not statistically significant. Conditions are abbreviated and color coded as follows: unpowered (NoPwr) (gray), NMM reflex Gains of 0.8, 1.2, 1.6, and 2.0 all with reflex Delay = 10 ms (G0.8, G1.2, G1.6, and G2.0, respectively) (green), NMM reflex Delays of 10, 20, 30, and 40 ms all with a reflex Gain = 1.2 (D10, D20, D30, D40, respectively) (blue), and a high-Gain-high-Delay condition (G2.0 D40) (black).