Development of a Soft Robotic Device for Rehabilitation and Assistance of the Upper Limb for People With Neurological Disorders

Usability of the FRONTIER Soft Exoskeleton as Assessed by the System Usability Scale (SUS) Total Score

Device usability will be measured using the 10-item System Usability Scale (SUS) following use of the FRONTIER soft exoskeleton prototype. Each item is rated on a 5-point Likert scale, and item scores are converted and combined to obtain a total score ranging from 0 to 100 points. Higher scores indicate greater perceived usability of the prototype. Device usability represents the primary feasibility-related outcome of the study and does not assess changes in participants' health status. SUS total scores will be reported separately for healthy volunteers and participants with chronic acquired brain injury.

Difference in Mean Normalized Surface Electromyography (sEMG) Amplitude Between Robotic-Assisted and Unassisted Movements

Muscle activity during upper-limb movements will be recorded using surface electromyography (sEMG) under two conditions: with and without assistance from the FRONTIER soft exoskeleton. sEMG amplitude will be quantified using the root mean square (RMS) and normalized to the maximum voluntary contraction, expressed as a percentage of maximum voluntary contraction (%MVC). For each participant, the mean normalized RMS amplitude across the predefined muscles and movement repetitions will be calculated for each condition. The reported outcome will be the within-participant difference between the robotic-assisted and unassisted conditions.

Mean Difference in Upper-Limb Range of Motion Between Robotic-Assisted and Unassisted Movements

Upper-limb range of motion will be measured during shoulder, elbow, and forearm movements performed with and without assistance from the FRONTIER soft exoskeleton. For each movement, range of motion will be calculated as the difference between the maximum and minimum joint angles recorded using inertial sensors. For each participant, the differences in range of motion between the robotic-assisted and unassisted conditions will be averaged across all predefined movements to obtain a single mean difference. Positive values indicate a greater overall range of motion with robotic assistance.

NASA Task Load Index (NASA-TLX) Overall Workload Score After Robotic-Assisted Testing

Perceived workload associated with use of the FRONTIER soft exoskeleton will be measured using the NASA Task Load Index (NASA-TLX). The questionnaire assesses six dimensions: mental demand, physical demand, temporal demand, performance, effort, and frustration. Each dimension is rated on a scale from 0 to 100 points. The overall workload score will be calculated as the mean of the six dimension scores and will range from 0 to 100 points. Higher scores indicate greater perceived workload.

Mean Difference in Borg Category-Ratio 10 Fatigue Score Between Robotic-Assisted and Unassisted Movements

Perceived fatigue will be measured using the Borg Category-Ratio 10 scale (Borg CR10) immediately after each predefined shoulder, elbow, and forearm movement performed with and without assistance from the FRONTIER soft exoskeleton. Scores range from 0, indicating no fatigue, to 10, indicating maximal fatigue. For each participant, Borg CR10 scores will be averaged across the predefined movements for each condition. The reported outcome will be the within-participant difference between the robotic-assisted and unassisted conditions. Positive values indicate greater perceived fatigue with robotic assistance, whereas negative values indicate lower perceived fatigue with robotic assistance.