Fig. 2

The treadmill walking experimental setup, data collection, processing, and Hill-type neuromuscular model calibration. a Illustration of walking experimental setup. (1) Instrumented treadmill with two split belts and in-ground force plates. (2) 39 retro-reflective markers on participant’s lower body for lower limb kinematics measurements. (3) Four sEMG sensors to record signals from LGS, MGS, SOL, and tibialis anterior (TA) muscles. (4) A single US transducer to image both LGS and SOL muscles with the appropriate probe placement. (5) Ultrasound imaging machine to collect radio frequency data. (6) Computer screen to show B-mode ultrasound imaging. (7) Computer screen to show live markers and segment links of the participant. (8) 12 motion capture cameras to track markers’ trajectories. b Schematic illustration of the proposed sEMG-US imaging-driven HNM calibration. The weighted muscle activation for LGS or SOL combines both sEMG signals and US imaging. Red solid, black solid, and blue dashed lines with an arrow represent the input signals to HNMs, the intermediate sub-model output signals, and the unknown parameters adjustment, respectively