Background: The embodiment of a prosthesis can bring a series of benefits during the rehabilitation of people with amputation, such as improvement of motor control and sense of agency, in addition to optimizing the training process with the prosthetic limb. New therapeutic strategies capable of enhancing prosthesis embodiment are, therefore, a key point for better adaptation to and acceptance of prosthesis use. In this study, we developed a system and a new rehabilitation protocol using an EMG-based human-machine interface (HMI) to induce and enhance the embodiment of a virtual prosthesis.
Methods: This is a case series with seven people of both sexes with unilateral transfemoral traumatic amputation without previous use of prostheses. Participants performed a training protocol with the EMG-based HMI during the preprosthetic rehabilitation phase, composed of six sessions held twice a week, each lasting thirty minutes. This system was composed of myoelectric control of the movements of a virtual prosthesis immersed in a 3D virtual environment. Additionally, vibrotactile stimuli were provided on the participant’s back corresponding to the movements performed. The objectives were to evaluate the virtual prosthesis embodiment, to investigate motor learning during training with EMG-based HMI, and to determine whether vibrotactile stimuli could facilitate the perception of virtual limb movements. The embodiment was investigated from a set of physiological and behavioral measurements and reports before and after the training. Motor learning was assessed through performance analysis. To investigate the use of vibrotactile stimulation to guide virtual prosthesis movements, the performance was assessed during the virtual prosthesis control test without adding vision.
Results and conclusions: The different features evaluated throughout the protocol training consistently showed the induction and enhancement of virtual prosthesis embodiment and increased motor control. Therefore, this protocol using EMG-based HMI was shown to be a viable option to achieve the embodiment of a virtual prosthetic limb and to train motor control. Furthermore, the participants were able to guide the prosthesis based on vibrotactile stimuli, showing that this method can be used as an alternative sensorial path to be implemented in new therapeutic strategies and neuroprostheses to facilitate the movement perception of a prosthetic limb.