# Designing a User-Centered Inspection Device's Handle for the Aircraft Manufacturing Industry
## 4 Discussion
### Global Results
These data corroborated the participants' perceptions about physical comfort (presented in Section 3.1) since they pointed out that \"handle 3\" is the least comfortable. Regarding the angles of the elbow during the task, the level of flexion/extension was found mostly within an acceptable ergonomic range (\(\sim\)80\({}^{\circ}\) to 100\({}^{\circ}\)) while using any of the handles. The wrist flexion/extension and deviation are not ideal (\(\sim\)0\({}^{\circ}\)) but still in acceptable ranges [26]. In line with the previous results, the EMG data reveal that \"handle 1\" achieves advantages in terms of muscle effort, and it is important to avoid fatigue during the prolonged and/or repeated use of the inspection device (as defended by [28]). In this context, it is important to note that muscle fatigue can reduce the inspectors' capability to maintain the stability of the equipment during its real industry and prolonged use, compromising its efficiency during image capture. During manufacturing tasks, workers may be exposed to different biomechanical risk factors, such as the adoption of straining postures (e.g., extension/flexion and/or lateral deviation of the wrist), and the use of a handle tool/device could aggravate these factors [11]. Therefore, more granular assessments with IMU and EMG were used to provide more objective measurements of the handles, as defended by [18]. This seems to be an appropriate approach to include during the user-centered design of a novel device, supporting design decisions that could compromise biomechanical factors that occur with the type of handles. Summarily, our results demonstrate that  
1. According to the participant's perceptions, the most comfortable is \"handle 1\", and \"handle 3\" is the most uncomfortable;
2. All handles have a similar effect on the stability of the device and on the efficiency of the task (estimated by the partial times);
3. A statistically significant shoulder deviation relative to the neutral posture is induced \"handle 3\", which leads to higher joint biomechanical stress;
4. Different handles have a different impact on the EMG of the recruited arm, and generally, \"handle 1\" seems to contribute to a smaller muscle activity/effort. In the current study, to avoid the typical biomechanical problems detected in hand tools/devices used in aircraft manufacturing, the design of new handles has been developed and tested. The ergonomic assessment of these handles included subjective and quantitative metrics to achieve a comprehensive analysis and a better decision for the final handle design, as adopted by [43]. The results revealed that \"handle 3\" presents disadvantages in terms of perceived comfort and shoulder posture. Otherwise, the results reveal that \"handle 1\" brings advantages in terms of perceived comfort and muscle effort. In fact, it is important to avoid fatigue during the prolonged and/or repeated use of the inspection device (as defended by [28]) to prevent musculoskeletal injuries and burnout. In addition, in this context, it is important to note that muscle fatigue can reduce the inspectors' capability to maintain the stability of the equipment during its use, compromising its efficiency during many image captures.