Investigation of the Linear Relationship between Grasping Force and Features of Intramuscular EMG

Surface electromyography (sEMG) can be used to control prosthetic devices. However, intramuscular EMG (iEMG) has been proposed as an alternative control signal, since it provides advantages such as electrode implantation and more selective recordings. iEMG can potentially be used to develop more intuitive prosthetic devices but since only limited research is available within this area, further investigation is needed on the relationship between iEMG and force. An earlier study quantified the linear relationship between iEMG and grasping force, however, this was solely based on one feature and force ranging from 0-50 N. Therefore the aim of the present study was to quantify the linear relationship between grasping force and 14 different EMG features using the entire force range from 0 to 100 % Maximum Voluntary Contraction (MVC). Single-channel iEMG and sEMG were recorded concurrently from the muscle Flexor Digitorum Profundus (FDP) from 11 subjects who exerted four force profiles during power grasping. The Wilson Amplitude (WAMP) feature showed the best results for both sEMG and iEMG (R-2 > 0.9), where sEMG had a significantly higher mean R-2-value than iEMG (P = 0.044). However, the potential of using iEMG should be investigated further based on the predictive capabilities of the features.