# Evaluation of a Myoelectrical Arm for Transradial Computation in Functional Activities
## 4 Discussion
On the one hand, the statistical comparison was cautiously applied to some outcome measures. [PERSON] ranksum test [37], an equivalent to the t-test from a non-parametric category, was applied to the calculated value of joint angles, movement smoothness of hand module, vGRFs from the left side and right side, and four muscle activations at each normalized time point. On the other hand, we performed a direct comparison of task completion time, correlation coefficient values, and closeness to the Right, as the sample size was too small for each measure. As data are collected from more participants, the ranksum test will be utilized to compare all outcome measures to determine if there is a significant change in each measure. To evaluate the effect of the training program and sensitivity of the selected outcome measures, ideally, all markers in every time frame should be captured by the Vicon system when the participant performs a task. However, a few technical aspects of motion capture data analysis may have compromised the evaluation. During a motion capture trial, part of the markers that were attached to the torso and upper extremities were blocked either by moving arms or moving objects in certain time frames. As a result, no marker position data were available to be used to calculate the instantaneous shoulder and trunk angles and movement smoothness for those time frames and to calculate the correlation coefficient (r value). To maintain data integrity, those time frames were not counted when calculating the mean and standard deviation of joint angles, the jerk, and the r value. To improve the marker capture rate in the future, a well-calibrated task space will be prepared for the motion capture system by reducing the optical obstruction coming from the test environment and task setup; a standing desk will be utilized with minimal surface area as the testing platform to further reduce the interference on motion capture caused by surface reflection. A minimal surface area where task items were placed may impose some challenge on an individual acclimating to a prosthesis. However, based on the feedback from the participants and our clinician, we currently do not think small surfaces will be that limiting to the participants. What matters most is the height of the table relative to the participant. If a table is too low or too high, that can impact how they compensate. The size of the table itself is usually not an issue. Nevertheless, we will continue checking on whether the minimal surface would impose undue stress on each participant as the research goes on. The Ossur i-Limb used in this study has a passive wrist pronation/supination function and no wrist flexion/extension function, as a powered wrist function would add more length to the participant's left limb to make her arms look asymmetrical. The participant needed to use her right hand to manually set the wrist unit to the proper pronation/supination angle at the beginning of each task. The wrist was kept at this angle throughout each task, which might have compromised the evaluation of the training effect and the sensitivity of outcome measures. One aim of future research would be to test a myoelectric arm with a powered wrist unit in which the pronation can be controlled by muscle signals like the hand, whereas the flexion/extension would still be passive. There was an initial attempt to capture the finger movement to validate the gripping pattern of the hand module of the myoelectric arm by attaching the 4 mm markers to the anatomical landmarks on the fingers of the hand module during a preliminary evaluation on a device similar to Ossur i-Limb. However, these 4 mm markers turned out to be too small to be captured. Moreover, the Ossur hand module has a determined gripping pattern. Therefore, the finger markers were not attached during the actual i-Limb evaluation, as it might be redundant to capture the gripping pattern. The correlation coefficient value was used to assess object control by evaluating hand-eye coordination.