Novel instrumented insole algorithm accurately approximates plantar flexor loading

Abstract

Plantar flexor loading is critical for ambulatory function but there are few wearable solutions to monitor loading. The purpose of this study was to develop and validate a method to quantify plantar flexor loading using a commercially-available instrumented insole. Seven healthy young adults completed a battery of functional activities to characterize a range of plantar flexor loading which included single leg heel raise, step down, and drop jump as well as walking and running at comfortable speeds. Lower extremity trajectories were captured using motion capture and ground reaction forces were recorded with embedded force plates as well as the instrumented insole. Measurements of plantar flexor loading quantified by the instrumented insole were compared to ‘gold standard’ inverse dynamics. We found that the insole loading calculation of plantar flexor moment was accurate to within 4.2% on average compared to inverse dynamics across all activities. Additionally, the calculated wave forms were strongly correlated with inverse dynamics (R_xy > 0.928). Our findings demonstrate the utility and fidelity of a new method for measuring plantar flexor loading using a commercially available instrumented insole. By leveraging this new methodology, it is now feasible to prospectively track and eventually prescribe plantar flexor loading outside of the clinic to improve patient outcomes.