# Evaluation of a Myoelectrical Arm for Transradial Computation in Functional Activities
## 2 Methodology
### Outcome Measures  
The primary outcome measures refer to the upper body kinematics and muscle activations during the functional tasks and bimanual tasks of using the prosthesis, as well as the postural stability when standing to perform evaluation tasks. They include the following items: (1) Task completion time; (2) Angles of the trunk (tilt, list, and rotation) and left shoulder (flexion, abduction, and rotation); Trunk and shoulder angles were included as these segments will be engaged compensate for limitations in prosthetic function, which is inefficient and can lead to injury [28; 29]; Vicon angle convention table was used to define these angles. The trunk tilt, list, and rotation angles are absolute angles. The trunk tilt is measured as the angle in the laboratory sagittal plane between the projected sagittal thorax axis and the sagittal laboratory axis. The trunk list is measured between the projection into the plane of the transverse thorax axis and the projection into the plane of the laboratory transverse axis; the trunk rotation is measured between the sagittal axis of the thorax and the sagittal laboratory axis (axis closest to the participant's direction of progression) projected into the thorax transverse plane. The shoulder flexion, abduction, and rotation angles are relative angles. The shoulder flexion, abduction, and rotation are calculated between the projected sagittal-humerus axis and the sagittal-thorax axis around the fixed transverse axis of the thorax, between the transverse axis of the humerus and the transverse axis of the thorax around a floating sagittal axis, and between sagittal axis of the humerus and the sagittal axis of the thorax around a floating frontal axis, respectively [30]. Figure 2 provides a demonstration of these angle definitions in an OpenSim model [31]. We expect that the participant will become more adapted to the myoelectric arm after the completion of the training program. To put it into the perspective of joint angle change at post-evaluation, across all tasks, all three trunk angles should decrease as the participant would rely less on the trunk compensation, and shoulder flexion and abduction shoulder increase, whereas the shoulder internal rotation should decrease. (3) object control. The linear correlation coefficient (r value) is calculated to quantify the head and object coordination, which indicates how well the object is handled during the task. The value of r is between \(-1\) and \(1\). The head moves in phase with the object as r reaches \(1\), whereas the head moves \(180^{\circ}\) out of phase with the object as r reaches \(-1\). This outcome measure assesses the participant's ability to manipulate and interact with objects, which is critical for daily functional tasks. Improved object control (towards r = 1) indicates that the participant can use the myoelectric arm to grasp, release, and handle objects with precision more effectively, enhancing overall prosthetic functionality and quality of life [32]. (4) Smoothness of movement. Using the marker on the back of the hand, smoothness can be quantified as jerk using the derivative of acceleration of that marker. This outcome measure was selected as it directly reflects the control and precision with which the participant is able to replicate natural hand and arm movements using a prosthesis. Improved smoothness indicates enhanced coordination between the user's muscle signals and the prosthesis, contributing to more functional use in daily activities [16]. (5) Muscle activation. These data provide insights into the participant's neuromuscular coordination and the effectiveness of the training in optimizing prosthetic functionality [33].