Comparative Analysis of Force Myography and Electromyography Signals in Isokinetic Ankle and Knee Joint Motion

Exoskeletons aim to enhance mobility by integrating muscle-level biomechanics and by addressing limitations like personalized control, with sensing methods such as electromyography (EMG) and force myography (FMG) to provide biofeedback. Previous comparative analyses of EMG and FMG were focused on specific classification and regression tasks without accounting for the full range of motion (RoM) of the human joints. This paper presents a descriptive analysis of both FMG and EMG signals of eight leg muscles obtained in a user study with ten participants, comparing both signals and their variations across the complete RoM of the ankle and knee joints during isokinetic motion at four different joint angular velocities. Results indicate that FMG signals exhibit higher repeatability in maximum amplitude and the corresponding joint angle, though they show higher variability in the signals' full width at half maximum. While EMG features are influenced by changes in angular velocities, FMG signals appeared to be more susceptible to cross-talk caused by opposing muscle activities. This analysis contributes to a better understanding of the relationship between FMG and EMG and their potential applications in the control of assistive wearable technologies.