Musculoskeletal model for simultaneous and proportional control of 3-DOF hand and wrist movements from EMG signals

Recently, we proposed a musculoskeletal model to simultaneously predict motion along metacarpophalangeal (MCP) and wrist flexion/extension degrees-of-freedom (DOFs) from surface electromyography (EMG) signals. Since wrist pronation/supination is also functionally important, we extended the musculoskeletal model to simultaneously estimate wrist pronation/supination in addition to wrist and MCP flexion/extension from surface EMG signals of six corresponding muscles. Kinematic data and surface EMG signals were acquired synchronously from an able-bodied subject. The subject was instructed to perform single-DOF movements at fixed or variable speed and simultaneous 3-DOF movements at variable speed during the experiment. The model included six Hill-type actuators, each with a contractile element and a parallel elastic element. Seven parameters were optimized for each of the six muscles. The average Pearson's correlation coefficient (r) between measured and estimated joint angles across all trials was 0.91, indicating high positive correlation. The results demonstrated that the proposed model could feasibly simultaneously estimate 3-DOF joint angles during either independent-DOF or simultaneous 3-DOF movements from EMG signals. Our results promote the potential of the EMG-driven musculoskeletal model for clinical applications, such as prosthesis control.