Participants will undergo functional task training using the MyoTrain AR system, which includes the HoloLens 2 augmented reality head-mounted display, four HTC VIVE SteamVR kinematic trackers, eight surface EMG electrodes based on the Element hardware platform, and a desktop computer. Participants will be prompted to use a pattern recognition-based myoelectric controller to operate a virtual prosthesis and complete a simulation of the GaMA Cup Transfer Task.

Participants will be provided motor imagery exercises that involve brief attempts to move the missing limb in a similar manner to how they would control their pattern recognition system to strengthen their muscles. These exercises do not involve any real-time control feedback or functional assessment.

MyoTrain AR is a virtual prosthesis functional training system. From a hardware perspective it consists of an augmented reality head-mounted display (HMD), four SteamVR kinematic trackers, eight surface EMG electrodes based on the Element electrode platform, and a desktop computer to facilitate wireless communication between the various hardware components. From a software perspective, MyoTrain AR was developed in the cross-platform Unity 4.0 game development engine.

The time to successfully complete the entire task trial (all 4 cup movements) from start to finish; averaged over all successful trials.

The percentage time spent in grasp phase relative to the entire movement (each movement involves reach-grasp-transport-release phases). This measure compensates for the expected inter-relation of absolute grasp duration with overall time, specifically identifying if grasp (object handling) is the main culprit in overall prolonged movement times.

In contrast to other instruments, the ACMC does not require a specific set of tools or tasks. Instead, the proctor for the measure chooses an everyday activity, such as setting up a table for snacks or replanting a flower, that is relevant to the study population. As the participants perform the chosen task, a trained rater will assess their capacity for control of their myoelectric prosthesis as represented by 30 items reflecting 6 aspects of quality of myoelectric control. These 6 aspects are "the need for external support," "grip force and opening width," "coordination of both hands, "in different positions and in motion (timing)," "repetitive grip and release," and "the need for visual feedback." Each item is scored on a 4-point scale and converted into linear measures of myoelectric control using Rasch analysis methods on the ACMC website. This outcome measure permits evaluation of bimanual tasks as well as different planes and work spaces of prosthesis use.