The Impact of Back-supporting Exoskeletons for Manual Order Picking in Danish Warehouses - The RELAX Project - Protocol for an 18-month In-field Controlled Intervention Study

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.