## 1 Introduction  
There are different types of musculoskeletal disorders related to the physical work performed by workers, however, one common reason for these disorders is repetitive motions and their resulting fatigue. Musculoskeletal imbalance emerges when fatigue outruns a worker's recovery system, which is followed by musculoskeletal disorders. Overhead tasks are not only the main reason for shoulder problems, but also for neck-related musculoskeletal disorders. The head is positioned above the cervical spine and normally the head's weight is balanced around it for anatomical position. However, overhead work requires the head to look upward, so it leads to torsional forces around the neck. These torsional forces are reason for joint inflammation and pain due to the compression of facet joints [1]. The shoulder joints and their surrounding musculature are the most susceptible due to their high range of motion and flexibility, especially for over-the-head tasks. The rotator cuff muscles and several surrounding tendons are responsible for the stability of the shoulder joints. There are several shoulder problems, but this paper focuses on disorders caused by repetitive movements performed for long-term overhead tasks. Excessive use of the shoulders under these conditions can lead to inflammation and swelling of the bursa between the rotator cuff and acromion, which is known as subacomial bursitis. Work-related musculoskeletal disorders (WMSDs) generally occur due to repeated and sustained work activities at workshops [2]. The exact source location for these disorders may not be clearly defined because the neck, shoulder, and upper part of the arm operate as a functional unit. A further complication is that most musculoskeletal problems of this region are nonspecific and without well-defined diagnoses. Increasing mental pressure to produce more monotonous tasks also leads to WMSDs. WMSDs are a serious health problem for workers and an important issue for companies and governments due to a lack of efficiency and health costs. WMSDs are also one of the reasons for the loss of mobility and autonomy [3]. Relaxing the muscles and letting them rest is very important when performing repetitive tasks, but some special tasks require pre-defined motions to be performed in a certain time. Additionally, manufacturing speed is very important for companies due to high competition. Disorders related to the shoulder complex comprise 15.2%, which is the second highest, following back-related WMSDs [4]. [PERSON] et al. [5] indicated that monotonous, over-the-head work tasks are the major reason for shoulder WMSDs, and this risk rises to 65% if the arms are moved in a 90\({}^{\circ}\) anteversion and repeated for 10% of one shift. The execution time of a physical task is important, especially for car manufacturing lines, because the production speed is set and workers must adapt themselves to this speed to ensure that the required job is performed in time. [PERSON] et al. [6] clearly stated that unexpected work loss in the automotive industry is directly related to unergonomic working conditions. Automation efforts help to reduce the tasks that require handling tools and therefore potential WMSDs; however, there are still certain tasks for which precise human hand placement is necessary [7; 8]. There is a growing interest in occupational exoskeletons--wearable supporting systems--because of their capacity to augment the structural stability and durability of workers during work tasks [9]. For decades, exoskeletons have mainly been developed for the purpose of medical rehabilitation and military applications; nevertheless, industrial exoskeleton applications are at quite an early stage. Still, exoskeletons are good example for human machine interactions and reducing WMSDs [10; 11]. Exoskeletons can be classified based on their power source, i.e., active and passive [12].