Under pressure: design and validation of a pressure-sensitive insole for ankle plantar flexion biofeedback during neuromuscular gait training

Background: Electromyography (EMG)-based audiovisual biofeedback systems, developed and tested in research settings to train neuromuscular control in patient populations such as cerebral palsy (CP), have inherent implementation obstacles that may limit their translation to clinical practice. The purpose of this study was to design and validate an alternative, plantar pressure-based biofeedback system for improving ankle plantar flexor recruitment during walking in individuals with CP. Methods: Eight individuals with CP (11-18 years old) were recruited to test both an EMG-based and a plantar pressure-based biofeedback system while walking. Ankle plantar flexor muscle recruitment, co-contraction at the ankle, and lower limb kinematics were compared between the two systems and relative to baseline walking. Results: Relative to baseline walking, both biofeedback systems yielded significant increases in mean soleus (43-58%, p < 0.05), and mean (68-70%, p < 0.05) and peak (71-82%, p < 0.05) medial gastrocnemius activation, with no differences between the two systems and strong relationships for all primary outcome variables (R = 0.89-0.94). Ankle co-contraction significantly increased relative to baseline only with the EMG-based system (52%, p = 0.03). Conclusion: These findings support future research on functional training with this simple, low-cost biofeedback modality.