Upper Extremity Joint Torque Estimation Through an EMG-Driven Model

Cerebrovascular accidents like a stroke can affect lower limb as well as upper extremity joints (i.e., shoulder, elbow or wrist) and hinder the ability to produce necessary torque for activities of daily living. In such cases, muscles’ ability to generate force reduces, thus affecting the joint’s torque production. Understanding how muscles generate force is a key element to injury detection. Researchers developed several computational methods to obtain muscle forces and joint torques. Electromyography (EMG) driven modeling is one of the approaches to estimate muscle forces and obtain joint torques from muscle activity measurements. Musculoskeletal models and EMG-driven models require necessary muscle-specific parameters for the calculation. The focus of this research is to investigate the EMG-driven approach along with an upper extremity musculoskeletal model to determine muscle forces of two major muscle groups, biceps brachii and triceps brachii, consisting of seven muscle-tendon units. Estimated muscle forces were used to determine the elbow joint torque. Experimental EMG signals and motion capture data were collected for a healthy subject. The musculoskeletal model was scaled to match the geometric parameters of the subject. First, the approach calculated muscle forces and joint moment for simple elbow flexion-extension. Later, the same approach was applied to an exercise called triceps kickback, which trains the triceps muscle group. Individual muscle forces and net joint torques for both tasks were estimated.