## 2 Materials and Methods
### Verification of the Design: Interventions and Measurements  
Three healthy, right-handed volunteers participated in the interventions. The age, sex, weight, and height of the participants are provided in Table 1. None of the participants reported any musculoskeletal disorders. The participants were informed about the exoskeleton, testing procedure, and scope of the test. Written consent was taken from all the participants after the procedure was explained to them. There were two tasks defined for the measurements. The first task was named \"Task 1\", in which the participants were asked to perform flexions of their upper arm of up to 120 degrees (to activate the exoskeleton first), then to perform an extension back to 90 degrees (upper arm was aligned parallel to the ground), and wait at this position for one minute. While moving their upper arms, their forearms were also flexed by 90 degrees (forearm was aligned vertical to the ground), and they held a tool with their hand (see Figure 7a,b). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Age** & **Sex** & **Height (cm)** & **Weight (kg)** \\ \hline
33 & female & 176 & 62 \\
33 & male & 176 & 75 \\
34 & male & 185 & 78 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Participants information. Figure 5: View that shows the mechanism’s main torque-providing solution. Figure 6: Mechanism side view that shows force transmission. In the second task, named \"Task 2\", the participants were asked to perform flexions of their upper arms of up to 120 degrees again, then to perform an extension to 90 degrees from the anatomical position, and hold this position for one minute. However, their forearms were kept in line with their upper arms and their hands were positioned forward while holding the same tool (see Figure 7c,d). Before recording the data, they wore the exoskeleton and pretended to perform tasks to get familiar with the exoskeleton and its motions. After this, they performed the tasks as defined to them and rested 15 min between each session. They carried out both tasks three times with and without the exoskeleton. Task 1 was defined to simulate overhead assembly work and Task 2 was defined to simulate shoulder-level assembly, welding, and similar works. The activation patterns of the muscles that alter the gleno-humeral (shoulder), scapulthoracal (scapula-ribs), scapula-vertebral (scapula-spine), thoracal-vertebrae (back vertebrae), and lumbar vertebrae arthrokinematics were evaluated to prove the efficiency of the exoskeleton. Therefore, the EMG signals for the muscle activity were measured for the following ten muscles (see Figure 8): triceps brachii (TB), biceps brachii (BB), pectoralis major (PM), anterior deltoid (AD), middle deltoid (MD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and latissimus dorsi (LD). Figure 8: Muscles that measured EMG activation during tests: triceps brachii (TB), biceps brachii (BB), pectoralis major (PM), anterior deltoid (AD), middle deltoid (MD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and latissimus dorsi (LD). Figure 7: Views from tests: (**a**) Task 1 without exoskeleton; (**b**) Task 1 with exoskeleton; (**c**) Task 2 without exoskeleton; and (**d**) Task 2 with exoskeleton. NORAXON Ultium measurement hardware and myoMOTION analysis software (version MR 3 3.14.52) were used to measure and analyze the intramuscular electro potentials. The EMGs of the muscles were recorded at 2000 Hz using wireless sensors. The main technical specifications of the device are given in Table 2. The measurements were taken for one minute. The Root Mean Square (RMS) values over the entire period were calculated with the mean amplitude and peak values for each muscle separately. As an advantage of the passive exoskeleton design, there was not any electric or electromagnetic signal that may have interfered with the muscle signals.