This study investigates the long-term effects of implementing a passive back-support exoskeleton during manual order-picking work in a real-world warehouse environment. Work-related musculoskeletal disorders, particularly low back pain, are common among logistics workers due to frequent lifting, repetitive movements, and awkward postures. Although laboratory studies suggest that occupational exoskeletons can reduce biomechanical load, evidence from long-term, real-world workplace implementations remains limited.

The RELAX project is an 18-month controlled in-field intervention study conducted in two departments of a Danish warehouse. Approximately 90 full-time warehouse workers will participate. Workers in the intervention department will use a passive back-support exoskeleton during manual order-picking tasks, while workers in the control department will continue their work as usual.

The primary outcomes include sickness absence, employee turnover, perceived work intensity, and musculoskeletal discomfort. Secondary outcomes include productivity, user acceptance of the exoskeleton, and cost-effectiveness of the intervention. Outcomes will be assessed through company records, repeated questionnaires, and focus-group interviews over the 18-month period.

By combining longitudinal quantitative outcomes with qualitative process evaluation, the study aims to determine whether long-term use of a passive back-support exoskeleton can improve worker well-being and reduce work-related musculoskeletal burden without negatively affecting productivity. The results may inform workplace policies and future implementation of occupational exoskeletons in physically demanding industries.

Work-related musculoskeletal disorders (WMSDs) are among the most common occupational health problems worldwide. Workers employed in physically demanding sectors such as logistics frequently perform repetitive lifting, forward bending, and manual material handling tasks. These exposures place considerable mechanical strain on the musculoskeletal system and are associated with an increased risk of lower back pain, fatigue, and long-term sickness absence. Low back pain is particularly prevalent among manual workers and represents a major cause of reduced work ability, decreased quality of life, and economic costs for both employers and society.

In recent years, occupational exoskeletons have been introduced as a potential ergonomic intervention to reduce physical workload during demanding manual tasks. Occupational exoskeletons are wearable assistive devices designed to support the musculoskeletal system by redistributing loads and assisting body movements. Passive back-support exoskeletons in particular aim to reduce mechanical loading of the lower back during tasks involving forward bending and lifting. Laboratory-based studies have shown that these devices can reduce muscle activity in the trunk and may lower perceived effort during lifting tasks. However, most existing studies have been conducted in short-term laboratory environments or controlled simulations, and there is still limited evidence regarding the long-term effectiveness and feasibility of exoskeleton use in real workplace settings.

The complexity of real-world effects of occupational exoskeletons is an important aspect, as workplace environments and user acceptance are often dynamic. In addition to potential biomechanical benefits, factors such as usability, worker acceptance, productivity requirements, organizational practices, and long-term adherence can strongly influence the success of implementing exoskeleton use. Previous research suggests that although exoskeletons may reduce muscle load, they may also introduce challenges such as discomfort, perceived restrictions in movement, or changes in work behavior. Consequently, long-term field studies are needed to evaluate whether exoskeleton use leads to meaningful improvements in worker health and well-being without negatively affecting productivity or workplace safety.

The RELAX project (Reduction of the Lifting Load Among logistics workers through passive back eXoskeleton) was designed to address these knowledge gaps. The aim of the study is to investigate the long-term effects of implementing a passive back-support exoskeleton during manual order-picking tasks in a real-world logistics environment. The study focuses on outcomes related to worker health, well-being, organizational performance, and economic impact. Specifically, the project examines whether prolonged use of a back-support exoskeleton reduces sickness absence, employee turnover, perceived work intensity, and musculoskeletal discomfort while maintaining or improving productivity.

The study is conducted as an 18-month controlled in-field intervention at a logistics warehouse in Denmark. Approximately 90 full-time warehouse workers from two departments of the same company are expected to participate. One department will serve as the intervention group, where workers will use a passive back-support exoskeleton during physically demanding order-picking tasks. The other department will serve as the control group and will continue performing the same work tasks without exoskeleton assistance. The two departments operate under similar working conditions, including comparable workflows, temperature, and equipment, which allows for meaningful comparison between groups.

The device used in the present study is a passive back-support exoskeleton designed to reduce the mechanical loading of the lumbar spine during forward bending and lifting movements. The device functions without motors or batteries and instead uses a mechanical structure to transfer part of the load from the upper body to the pelvis and lower extremities. When a worker bends forward, the device provides supportive torque that assists the trunk and reduces the effort required from the back muscles. When the worker returns to an upright posture or walks, the assistance disengages, allowing normal movement. The device is lightweight (<3.0 kg), worn externally over work clothing, and adjustable to accommodate different body sizes.

To facilitate successful implementation of the intervention, a structured rollout process will be used. Workers in the intervention department will first participate in introduction sessions explaining the purpose of the project, the function of the exoskeleton, and safety considerations. Exoskeleton use will then be gradually introduced through a stepwise familiarization process that allows workers to adapt to the device over time. During this period, trained personnel and company representatives will provide technical and ergonomic support to ensure appropriate fitting and safe usage. Workers will be encouraged to use the device during physically demanding tasks but will remain free to remove or disengage it when necessary, reflecting normal workplace practice.

Data will be collected repeatedly throughout the 18-month study period. Both quantitative and qualitative methods will be used to evaluate the effects of the intervention. This mixed-methods approach allows the study to capture not only measurable outcomes but also the experiences and perspectives of workers and workplace stakeholders.

The primary outcomes of the study relate to worker health and well-being. These include sickness absence, employee turnover, perceived work intensity during work shifts, and musculoskeletal discomfort. Sickness absence and employee turnover will be obtained from company administrative records. Perceived work intensity and musculoskeletal discomfort will be assessed through standardized questionnaires completed by participants at regular intervals throughout the study. These measures will help determine whether the exoskeleton intervention reduces physical strain and improves workers' overall experience of their daily work tasks.

Secondary outcomes focus on organizational and implementation-related aspects of exoskeleton use. These include productivity, worker acceptance of the device, and economic evaluation of the intervention. Productivity will be assessed using company performance indicators, such as the number of packages handled per hour. Worker acceptance will be evaluated through questionnaires and focus-group interviews examining perceptions of comfort, safety, usability, and perceived impact on work performance. Qualitative interviews with workers and relevant stakeholders will also explore experiences with implementation, barriers and facilitators to adoption, and how the exoskeleton fits into daily work routines.

An additional objective of the study is to evaluate the economic implications of implementing occupational exoskeletons in a logistics workplace. The costs associated with acquiring and implementing the devices, including training and operational resources, will be compared with potential economic benefits such as reduced sickness absence, lower employee turnover, and maintained or improved productivity. These analyses will provide estimates of cost-effectiveness and return on investment from both company and societal perspectives.

In addition to quantitative outcome analyses, qualitative data from focus-group interviews will be analyzed using thematic analysis to identify key themes related to user experiences, implementation processes, and contextual factors affecting exoskeleton adoption. Integrating qualitative and quantitative findings will provide a more comprehensive understanding of how occupational exoskeletons function in real-world settings and how they may influence both workers and organizations.

The RELAX project addresses an important gap in occupational health research by evaluating the long-term effects of exoskeleton use in an authentic workplace environment. Many previous studies have focused primarily on short-term biomechanical outcomes measured in controlled laboratory settings. By contrast, this study evaluates the broader impacts of exoskeleton implementation, including worker well-being, organizational outcomes, and economic considerations.

The findings of this study may contribute valuable evidence for employers, occupational health professionals, technology developers, and policymakers interested in improving working conditions in physically demanding industries. If passive back-support exoskeletons prove to reduce physical strain and improve worker well-being without negatively affecting productivity, they may represent a promising ergonomic intervention for preventing work-related musculoskeletal disorders in the logistics sector and other industries involving manual material handling.

Conversely, if the study identifies limitations, unintended effects, or barriers to successful implementation, these findings will also be important for guiding future research, device development, and workplace policy decisions. Overall, the RELAX project seeks to generate robust real-world evidence on the effectiveness, feasibility, and sustainability of occupational exoskeletons as a workplace intervention.

Inclusion Criteria:

• age 18-65 years at enrolment
• full-time employment in the current work department
• no major pain or injuries affecting daily work tasks

Exclusion Criteria:

• anthropometric characteristics preventing adequate fit of the exoskeleton
• part-time employment
• pregnancy or anticipated prolonged absence from work during the study period (standard vacation not included)

If a participating worker from either the intervention or control group transfers to another department within the company during the intervention period for reasons unrelated to the intervention, the participant will be excluded from the study. Such cases will be classified as dropouts and the corresponding data will be reported as lost to follow-up.

The Study Protocol and Informed Consent Form (ICF) will be made publicly available prior to initiation of the intervention. The Statistical Analysis Plan (SAP) will be made available prior to conducting the statistical analyses and before completion of the intervention. All data will be made publicly available through scientific publications or supplementary materials upon completion of the study.

All supporting materials and scientific publications will be published open access.