Manual materials handling (MMH) is common in warehouse work, and often includes tasks causing high physical requirements on the manual workers involved. An outcome of these strenuous tasks due to a challenging physical environment is often overexertion which can cause attrition and, in some cases, lead to sickness absences and work-related musculoskeletal disorders (WMSDs). Musculoskeletal disorders are the main cause to disabling injuries in United States businesses, leading to an annual direct cost of $14 billion. These disorders are often accompanied by low-back pain, causing the most years lived with disability worldwide. Additionally, in Denmark, 37% of all work-related disorders are related to musculoskeletal load, making it the biggest contributor to sick leave. In 2019, the annual cost of work-related injuries was estimated to USD 600 million.

Wearable personal assistive systems like exoskeletons were initially designed for rehabilitation purposes, e.g., walking aid, and later for military applications. Recently, exoskeletons have been introduced for occupational use. According to the European Agency for Safety and Health at Work (EUOSHA) body-worn exoskeletons are right now being implemented as assistive devices to manual labour at workplaces all over Europe. Occupational exoskeletons were first seen in Danish industrial companies in 2019, where it was adopted by automotive industry. Exoskeletons are an attractive solution to the issues related to the physical loads carried out by workers during MMH. Still, there is a lack of studies examining the benefits, risks, and barriers to the implementation of exoskeletons in industry. Most of the research on occupational exoskeletons have been conducted in laboratory setups or by simulating work-tasks in 'ideal' conditions, while in-situ exoskeletons use to reflect real-life aspects have almost never been investigated. Despite the lack of research, exoskeletons have been proven beneficial since lower muscle load indicated by surface electromyography and lower discomfort have been reported. Yet, several limitations because of wearing the exoskeletons have been underlined: modifications of the kinematics in form of lower range of motion and increased heart rate. Additionally, it is found that unloading of a specific joint can induce increased loading of other body areas, leading to higher fatigue and exertion, besides mixed effects on heart rate and usability.

Current research indicates that occupational exoskeletons decrease the biomechanical load during MMH. This can lead to a positive effect towards the development of muscle fatigue of target areas of the body and work-related musculoskeletal disorders. Yet, there are many unexplored aspects of the implementations of exoskeletons to occupational use regarding neuromuscular coordination, changes in kinematics, discomfort, postural strain (due to the weight of the exoskeleton) and difficulty for workers to perform smooth movement.

This underlines the need to clarify the pros and cons of occupational exoskeleton use. To improve the implementation of the exoskeletons in the industry, it is important to determinate which working tasks is suitable for which exoskeletons. Furthermore, it is relevant to identify which environmental conditions that may contraindicate the use of occupational exoskeletons, e.g., working in a confined space or the need of high physical precision. Concluding, to explore the important factors driving the adoption of occupational exoskeletons for industrial use, in particular identification of key facilitators and barriers, a large-scale of field studies is needed, before being able to identify the benefits and limitations of the implementation of exoskeleton use. Such studies should include a wide range of workers and working tasks and include health-relevant outcomes like musculoskeletal disorders.

Thus, the purpose of this study is to investigate the long-term effects of exoskeleton-use during MMH. In this study, the warehouse workers will participate in a 24-week randomized controlled trial (RCT) investigating the prospective effects of a passive back-exoskeleton-use. The exoskeleton used in the present study is based on initial findings of a 5-week trial, which showed that this exoskeleton induced higher acceptance among the workers (attendance), and lower discomfort. During the intervention, parameters of muscular and kinematic changes, perceived effort, comfort and performance, liking, exertion, musculoskeletal discomfort, and productivity will be monitored.