The Impact of Back-supporting Exoskeletons for Manual Order Picking in Danish Warehouses - The RELAX Project (RELAX)

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

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Work-Related Musculoskeletal Disorders
• Intervention / Treatment: Device: Use of an occupational passive back-exoskeleton

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 90
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Lasse S. Jakobsen, PhD; Phone Number: 0045 72332998; Email: lsja@hst.aau.dk
• Study Contact Backup: Name: Pascal Madeleine, Professor; Phone Number: 0045 99408833; Email: pm@hst.aau.dk

Study Locations

• Denmark
  • Aalborg, Denmark, 9000
    • Aalborg University
    • Contact: Lasse S. Jakobsen, PhD; Phone Number: 0045 72332998; Email: lsja@hst.aau.dk
    • Contact: Pascal Madeleine, Professor; Phone Number: 0045 99408833; Email: pm@hst.aau.dk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Exoskeleton group; Group receiving intervention	Device: Use of an occupational passive back-exoskeleton; Use of the IX Back AIR (SuitX by Ottobock) for 18 months during daily order picking tasks
No Intervention: Control Group; Group receiving no intervention

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Musculoskeletal Discomfort	Assessed using the Cornell Musculoskeletal Discomfort Questionnaire (CMDQ), completed monthly by workers as part of the questionnaire battery. The questionnaire includes three questions on 1) how often they experienced discomfort during the last workweek (1-5, 5 being worst), 2) how uncomfortable it was (1-3, 3 being worst), and 3) if the discomfort interfered with their ability to work (1-3, 3 being worst). All questions will be answered for separate body regions. Analyses will primarily focus on reports of back discomfort.	Reported at baseline, Month 3, Month 6, Month 9, Month 12, Month 15, and Month 18.
Perceived Work Intensity	Assessed using two 10-point Likert-scale questions on 1) how much they exert themselves during a shift and 2) how exhausted they feel at the end of a shift.	Reported at baseline, Month 3, Month 6, Month 9, Month 12, Month 15, and Month 18.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sickness Absence	Measured as the number of days of sick leave per month as reported by the company. To assess whether sick leave was related to musculoskeletal issues, the questionnaire will include the question: "Have you had any sick leave related to musculoskeletal discomfort within the last month?"	Reported at baseline, Month 3, Month 6, Month 9, Month 12, Month 15, and Month 18.
Employee Turnover	Measured as the number of monthly resignations in the respective department as reported by the company.	Time-to-event. Reported as the timepoint (in months) from baseline, when the resignation occurs.
Productivity	Productivity is a key performance indicator monitored by the company reported in packages per hour for each individual worker. In this study productivity will be reported as a weekly average.	Weekly during the 18-month intervention (Baseline to month 18).

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Process evaluation	A process evaluation will be conducted to support interpretation of the intervention outcomes and to document implementation fidelity, user acceptance, and contextual factors influencing exoskeleton use. Process evaluation data will be collected every 6th month throughout the 18-month intervention period. Qualitative process data will be collected through repeated focus-group interviews with workers from the intervention group and with relevant stakeholders. The interviews will explore experiences with BSE use, integration into daily work routines, perceived benefits and drawbacks, and organizational factors affecting implementation.	Reported at baseline, Month 3, Month 6, Month 9, Month 12, Month 15, and Month 18.
Exoskeleton use	During the intervention period, workers will report daily exoskeleton use using operational logs. Specifically, usage will be recorded through a stamp system each time the exoskeleton is used. In this study exoskeleton use will be reported as a weekly average.	Weekly during the 18-month intervention (Baseline to month 18).
Exoskeleton evaluation / User acceptance	Evaluations of the exoskeleton will be conducted using a 6-item 10-point Liker-Scale questionnaire: Q1: What is your perception of the overall fit and comfort of the exoskeleton when performing your job? Q2: What is your perception of the thermal comfort typically (and/or feelings of sweatiness) when using the exoskeleton? Q3: What is your perception of balance (or any sense of imbalance) while using the exoskeleton? Q4: Do you feel that your range of motion was at all limited while using the exoskeleton? Q5: When using the exoskeleton to perform your job, how do you think this affected your overall safety? Q6: Overall, does using the exoskeleton positively or negatively affect your performance? Additionally, the questionnaire will include the open-ended questions: Q7: What do you most like about the exoskeleton? Q8: What do you least like about the exoskeleton? Q9: If you could change anything about the exoskeleton, what would you change?	Reported at baseline, Month 3, Month 6, Month 9, Month 12, Month 15, and Month 18.

Collaborators and Investigators

• Sponsor: Aalborg University
• Collaborators: Aarhus University Hospital; National Research Centre for the Working Environment, Denmark; Royal College of Surgeons, Ireland; Ecole Normale Supérieure de Rennes
• Investigators: Study Director: Pascal Madeleine, Professor, Aalborg University

Publications and helpful links

General Publications

• 1) J De Kok. Work-related musculoskeletal disorders: prevalence, costs and demographics in the EU European Risk Observatory Report. European Agency for Safety and Health at Work (2019) EU OSHA.
• 2) S Skals, R Bláfoss, MS Andersen, M De Zee, LL Andersen. Manual material handling in the supermarket sector. Part 1: Joint angles and muscle activity of trapezius descendens and erector spinae longissimus, Applied Ergonomics. 92 (2020) 103340.
• 3) JN Katz. Lumbar disc disorders and low-back pain: socioeconomic factors and consequences, JBJS. 88 (2006) 21-24.
• 4) MS. Popova, SP Nikolova, & SI Filkova. Demographic and Occupational Determinants of Work-Related Musculoskeletal Disorders: A Cross-Sectional Study. Journal of Functional Morphology and Kinesiology (2025) 10(2), 137.
• 5) D Hoy, C Bain, G Williams, L March, P Brooks, F Blyth, ... & R Buchbinder. A systematic review of the global prevalence of low back pain. Arthritis & rheumatism (2012) 64(6), 2028-2037.
• 6) S Toxiri, MB Näf, M Lazzaroni, J Fernández, M Sposito, T Poliero, et al. Back-Support Exoskeletons for Occupational Use: An Overview of Technological Advances and Trends, IISE Transactions on Occupational Ergonomics and Human Factors. 7 (2019) 237.
• 7) H Kazerooni, W Tung, M Pillai. Evaluation of Trunk-Supporting Exoskeleton, Proceedings of the Human Factors and Ergonomics Society Annual Meeting. 63 (2019) 1080.
• 8) S Crea, P Beckerle, M De Looze, K De Pauw, L Grazi, T Kermavnar, et al., Occupational exoskeletons: A roadmap toward large-scale adoption. Methodology and challenges of bringing exoskeletons to workplaces, Wearable Technology 2 (2021) e11.
• 9) J Howard, VV Murashov, BD Lowe, M Lu. Industrial exoskeletons: Need for intervention effectiveness research, American Journal Industrial Medicine 63 (2020) 201-208.
• 10) SE Kranenborg, C Greve, MF Reneman, CC Roossien. Side-effects and adverse events of a shoulder- and back-support exoskeleton in workers: A systematic review, Applied Ergonomics 111 (2023) 104042.
• 11) J Theurel, K Desbrosses. Occupational exoskeletons: overview of their benefits and limitations in preventing work-related musculoskeletal disorders. IISE Transactions on Occupational Ergonomics and Human Factors. 7 (2019) 264-280.
• 12) MA Nussbaum, BD Lowe, M De Looze, C Harris-Adamson, M Smets. An Introduction to the Special Issue on Occupational Exoskeletons, IISE Transactions on Occupational Ergonomics and Human Factors. 7 (2020) 153.
• 13) M Bär, B Steinhilber, MA Rieger, T Luger. The influence of using exoskeletons during occupational tasks on acute physical stress and strain compared to no exoskeleton - A systematic review and meta-analysis, Applied Ergonomics. 94 (2021) 103385.
• 14) S Madinei, S Kim, JH Park, D Srinivasan & MA Nussbaum. A novel approach to quantify the assistive torque profiles generated by passive back-support exoskeletons (2022) Journal of Biomechanics, 145, 111363.
• 15) S Kim, MA Nussbaum, M Smets, S Ranganathan. Effects of an arm-support exoskeleton on perceived work intensity and musculoskeletal discomfort: An 18-month field study in automotive assembly, American Journal Industrial Medicine 64 (2021) 905-914.
• 16) A. Hedge, S. Morimoto, S., & Mccrobie, D. (1999). Effects of keyboard tray geometry on upper body posture and comfort. Ergonomics, 42(10), 1333-1349.

Study record dates

Study Major Dates

• Study Start (Estimated): August 1, 2026
• Primary Completion (Estimated): January 31, 2027
• Study Completion (Estimated): October 31, 2029

Study Registration Dates

• First Submitted: April 20, 2026
• First Submitted That Met QC Criteria: April 24, 2026
• First Posted (Actual): May 1, 2026

Study Record Updates

• Last Update Posted (Actual): May 7, 2026
• Last Update Submitted That Met QC Criteria: May 1, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Ergonomics; Musculoskeletal Disorders; Assistive Technology; Warehouse; Occupational Exoskeletons; Manual Materials Handling
• Additional Relevant MeSH Terms: Musculoskeletal Diseases
• Other Study ID Numbers: AAU-LBK1268

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Sharing Time Frame: 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.
• IPD Sharing Access Criteria: All supporting materials and scientific publications will be published open access.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No