Infrared motion capture cameras

On the first visit, we fitted the device and determined each participant’s preferred moderate-to-fast walking speed that fell within the dimensionless walking speed range of 0.4 – 0.5 (Moissenet, Leboeuf, & Armand, 2019 (link)). Participants then completed two treadmill walking conditions with at least 20-minute rest in between: 1) Exo-Adaptation: 30-minute walk with the device as it provided bilateral plantarflexion and dorsiflexion assistance and 2) Shod: 6-minute walk wearing shoes and without the device. We collected O₂ and CO₂ volumetric rates using a portable metabolic system (K5, Cosmed) and bilateral soleus activity using a wireless electromyography (EMG) system (1926 Hz; Trigno, Delsys) throughout the entire trial for the two conditions. We also collected lower limb kinematic data using ten infrared motion capture cameras (120Hz; Vicon Motion Systems, Oxford, UK), kinetic data from an instrumented treadmill (960 Hz; Bertec, Columbus, OH), and bilateral muscle activities at the tibialis anterior, vastus lateralis, and semitendinosus. Prior to the Exo-Adaptation trial, all participants had minimum experience (< 1 minute) walking with the exoskeleton within the past month.

On the second visit, participants walked under the following conditions: 1) Baseline: walking wearing shoes without the device, 2) Resisted: walking with bilateral plantar flexor resistance and biofeedback provided to the right leg. Participants did not have any exposure to resistance or biofeedback before the test. Biofeedback was provided unilaterally during this protocol to make it easier for participants to focus on a single limb. A set speed of 1 m/s was used for all participants except for P6, who walked at 0.75 m/s due to functional limitations. To minimize learning and ordering effects, all participants completed two one-minute trials following the order Baseline, Resisted, Resisted, Baseline; at least 2 minutes of rest was provided between conditions. We collected lower limb kinematic data using ten infrared motion capture cameras (120Hz; Vicon Motion Systems, Oxford, UK), kinetic data from an instrumented treadmill (960 Hz; Bertec, Columbus, OH), and bilateral soleus activity using a wireless EMG system, for the entire 1-minute of each trial.