Mixed-Methods Evaluation of the Potential for Back-Support Exoskeletons to Assist Emergency Medical Services Clinicians in Performing Patient-Handling Tasks

Introduction

Emergency medical services (EMS) clinicians are exposed to high risks of work-related musculoskeletal disorders (WMSDs), due to the physically demanding nature of their jobs, including handling high loads in extreme non-neutral postures during patient handling and performing cardiopulmonary resuscitation procedures (Bureau of Labor Statistics, 2024). Among the most common WMSDs in this profession, low back pain is particularly prevalent, affecting 30%–80% of EMS personnel every year (Friedenberg et al., 2022). Existing interventions for preventing WMSDs include increased use of specialized equipment, such as power stretchers and stair chairs, as well as improved guidelines for safe patient handling (e.g., USFA, 2022). However, despite some improvements in outcomes, injury rates continue to be high, thereby underscoring the need for innovative interventions that may help reduce WMSDs in EMS work. In this study, we aimed to assess the perceptions of EMS workers regarding the benefits and limitations of using back-support exoskeletons (BSEs) for their work, and to quantify the biomechanical effects of BSE use on some common patient transfer techniques regularly used in EMS work.

Occupational BSEs have recently gained attention as a new ergonomic intervention to control and prevent work-related lower back disorders (Bär et al., 2021). BSEs are wearable systems designed to provide external forces/torques assisting back extension. Emerging evidence suggests that BSE use can lead to substantial physical load reduction by decreasing lumbar muscle activity, trunk-extension torque, perceived exertion, and metabolic costs, particularly during tasks involving repetitive/heavy lifting and awkward postures (Alemi et al., 2020). However, there is limited evidence supporting the use of BSEs for EMS workers.

Some earlier investigations have examined the effects of using BSEs on patient-handling tasks relevant to EMS workers (Mukherjee et al., 2024; Park et al., 2024). Park et al. (2024) found that BSE use can lead to a decrease in trunk muscle activity, low back discomfort, and perceived exertion among a sample of young and healthy adults (not trained EMS workers). Meanwhile, Mukherjee et al. (2024) reported that BSE use can reduce EMS workers’ hamstring muscle activity in stair-chair carry and CPR tasks, but that their perceived exertion was not significantly affected by BSE use (Mukherjee et al., 2024). Neither of these studies included an assessment of conditions that may impact EMS workers’ acceptance of BSEs and integration into their regular work. This study seeks to fill this gap by addressing two research questions: (1) What are the perceptions of EMS workers regarding the benefits and limitations of adopting BSEs for their regular work? (2) How does the use of passive vs. powered BSE designs impact muscle activity and perceived exertion/discomfort during commonly performed patient transfer techniques?

Methods

We conducted two separate studies, each addressing a distinct research aim. Both studies were approved by the Institutional Review Board of Clemson University (protocol code 2023-0344).

For the first study, a convenience sample of 35 EMS workers aged 37.3 (SD 11.5) years, including 19 males and 15 females, was recruited. Six focus groups of 3 to 9 participants were conducted. The study participants were introduced to a variety of BSEs (BackX^TM: rigid and passive BSE, US Bionics, USA; Apex: soft and passive BSE, HeroWear, USA; Apogee: rigid and active BSE, German Bionic, Germany), with the opportunity to try any BSE and perform common movements such as squatting and lifting. The focus group included questions on perceptions of exoskeleton designs, opportunities and barriers for implementation in their work settings, potential impacts on job performance and safety, workflow integration considerations, and any other environmental challenges unique to EMS work. Responses were audio-recorded, and the results were anonymized and transcribed for theorical thematic analysis to identify significant themes. The key themes that emerged have been identified and summarized.

For the second study, eight EMS workers aged 33 (SD 13) years, including six males and two females, performed multi-person cooperative patient-handling tasks using a mannequin with a mass of 45 kg, and with the assistance of trained personnel. Three BSE conditions involved were Apex, Apogee, and no BSE (control condition). Each participant completed five patient-handling tasks in each BSE condition: (1) direct ground lift (three-person lift), (2) extremity lift (two-person lift), (3) power lift (two-person lift), (4) lateral transfer with slide sheet pulling (three-person transfer), and (5) lateral transfer with slide sheet pushing (three-person transfer). Each task was replicated twice, resulting in 30 trials for each participant (three BSE conditions × 5 tasks × 2 replications).

For each trial, muscle activities were recorded bilaterally from eight muscle groups, including the upper trapezius, anterior deltoid, lumbar erector spinae, thoracic erector spinae, abdominis, external oblique, vastus lateralis, and biceps femoris. Subjective ratings (i.e., perceived exertion and discomfort) were obtained. Outcome measures included 50th and 95th percentile of muscle activity (shoulder, back, abdomen, biceps femoris, and vastus medialis), perceived exertion, and perceived discomfort (shoulder, back, and leg). Friedman tests were performed on each outcome measure, including the BSE condition as a within-subject factor. Significant effects were followed by post hoc pairwise comparisons using Wilcoxon tests. Statistical significance was determined when p < .05.

Results

From the first study, the focus group identified five key themes of decision-making considerations for exoskeleton adoption, including perceived benefits , use cases , device-related factors , job-specific factors , and workflow integration . Within these themes, multiple factors supporting the adoption of BSE were captured, such as BSEs being potentially helpful for awkward lifting in restricted spaces where assistance from other people or specialized equipment could not be used. In contrast, there were also factors that could deter the use of BSEs. For instance, some EMS workers mentioned unintended side effects, movement constraints, and potential limitations with battery life. There were also questions and concerns raised by the EMS workers, such as task compatibility (e.g., hindrance during chest compression resuscitation), unpredictable environments (e.g., scenes in the forest), don/doff time and location (e.g., at the station or on the scene), as well as their capacity to manage additional equipment when the BSE is donned.

From the second study, as compared to the control (no BSE) condition, using the Apogee decreased back muscle activity by 10-30% during the direct ground lift, extremity lift, lateral transfer with slide sheet pulling and pushing (all p < .05). Apogee use also led to a ~15% decrease in abdominal muscle activity during extremity lift and power lift, as well as a ~20% decrease in biceps femoris muscle activity during lateral transfer with slide sheet pulling and pushing (all p < .03). The objective outcomes aligned well with the 30% to 35% decrease in perceived exertion reported by the participants when using the Apogee for the direct ground lift, extremity lift, and power lift (all p < .03). Additionally, use of the Apogee led to decreased shoulder discomfort during lateral transfers and also reduced leg discomfort during extremity lift (p < .05). Use of the Apex was associated with a 13% decrease in back muscle activity during extremity lift only (p < .04). However, the Apex led to greater changes in subjective ratings than the objective measures: a ~30% decrease in perceived exertion during power lift and lateral transfer with slide sheet pulling, a ~50% decrease in shoulder discomfort and ~60% discomfort in back discomfort during lateral transfers (p < .02) were reported.

Discussion

The focus group study helped discover several specific factors impacting or facilitating the adoption of BSEs specific to EMS work; and the effects of the devices in biomechanic exposure. Based on the perceived benefits reported in the results, the Apex exoskeleton appears to offer more advantages and can be applied across various use cases, including patient handling in confined spaces and tasks involving awkward postures. In contrast, the Apogee was recommended for specific tasks involving heavier patients, such as lifting obese individuals in open or non-confined pre-hospital environments.

The biomechanics exposure investigation showed that BSE use led to a decrease in EMS workers’ muscle activity during a variety of patient-handling tasks, with the magnitude of reduction being task-specific. The Apogee demonstrated more biomechanical benefits than the Apex during the patient handling tasks included in this study. A previous study by Mukherjee et al. (2024) investigated the effect of Apex among EMTs on muscle activity during different simulated tasks. The authors were not able to find a significant reduction in back muscle activity or perceived exertion. In contrast, in our study, Apex was found to be associated with significant reductions in perceived exertion during the power lift and lateral transfer with sheet pulling.

Overall, this study followed a systematic approach to explore the benefits and limitations of BSEs in EMS that may guide potential adoption in EMS work practices and equipment. However, it is important to recognize that the sample size of the study was limited, and that the participants were from the same EMS system within the local community. Future studies should aim to seek answers to some of the questions and concerns posed by the EMS workers, such as storage of BSEs from their ambulance and dispatch centers, actual retrieval methods, donning, doffing, and quantifying work performance and safety when using BSEs in field trials.