Abstract
Emergency medical technicians (EMTs) have a high prevalence of low back injuries and low-back pain. Low back exoskeletons, that have proven to be effective tools in injury prevention in industry, can be seen as a potential solution to reducing the risk of injury for EMTs. The aim of this study was to evaluate user perception and perceived workload of EMTs for a low back exoskeleton. Trained EMTs performed various equipment and patient handling tasks as well as tasks providing emergency care in a control condition and while wearing a low back exoskeleton. While overall perception of the exoskeleton was positive, EMTs did not perceive the low back exoskeleton to be useful for their job.
Emergency Medical Technicians (EMTs) often must perform tasks that strain their lower back like carrying and lifting patients, handling heavy stretchers, etc. These tasks place EMTs at high injury risks, some exceeding spinal compression injury risk guidelines (Armstrong et al., 2020; Maguire et al., 2005). Consequently, ~34.6% of full-time EMTs experience an injury at work, with the most common injury site being the lower back (Maguire et al., 2005). However, workplace redesign is not an option for the EMTs since they often have to work in unpredictable, safety critical contexts. Therefore, in order to reduce the injury risk to EMTs, an ergonomic intervention that can improve the lifting capacity of the workers and reduce the strain on their lower back is needed. One such intervention that is already widely adopted in diverse manufacturing and material handling industries is a passive low-back exoskeleton (LBE). Passive LBEs significantly decrease spinal compression of the L5-S1 joint by about 13% and increase user endurance time by 14% for repetitive lifting tasks (Kermavnar et al., 2021). However, the benefits of LBEs are very task specific. For example, LBEs are typically not well suited for tasks that require diverse lifting postures and movements like ladder climbing, stair climbing, load carrying, and awkward walking gait and posture. Therefore, this study investigated their effectiveness for tasks that are more ecologically valid for EMS work.
18 male and 2 female EMTs from a local Emergency Medical Services department volunteered for the experiment. Participants performed tasks from the Physical Agility Test (PAT), which is a timed event designed to simulate critical physical tasks performed by EMTs during emergency situations (FCESED). Participants performed a 6-task circuit which included lifting a backboard with a patient dummy, stair climbing with equipment (45lb), stair climbing with a 75-lb barbell, pulling and pushing a stretcher into and out of an ambulance, cardiopulmonary resuscitation (CPR), and another backboard lift. Participants were fully trained EMTs who performed the circuital tasks with (exoskeleton condition) and without (control condition) the support of an LBE (Herowear, Nashville, Tennessee). Perceived workload measured via NASA Task load index (NASA TLX), discomfort (on a scale from 0 to 10), rate of perceived exertion (RPE, scale from 6 to 20) and perception of the exoskeleton (measured using the technology acceptance model: TAM, and The Exosystem Use Intent: EUI) between the control and exoskeleton conditions.
Across all the tasks, RPE and mental demand (from NASA TLX) remained comparable across the control and the exoskeleton conditions. However, after the entire circuital exercise participants reported significantly lower scores in the exoskeleton than the control condition for physical demand (p = 0.044) temporal demand (p = 0.006), and effort (p = 0.036). Participants reported significantly lower discomfort scores for the lower back (p <0.001) and shoulder (p = 0.015) in the exoskeleton compared to the control condition. TAM scores revealed that participants scored higher on clear and understandable interactions (p = 0.015) but lower on ease of learning to use exoskeletons (p = 0.016) after performing the circuit tasks with the LBE, they also reported lower effectiveness on the job with the use of exoskeletons (p = 0.08). The average EUI score for the EMTs after using the exoskeletons indicated a positive intention towards using an exoskeleton for EMS specific tasks.
The results suggest that exoskeletons can reduce perceived physical demand, temporal demand, and effort while improving comfort levels for EMTs. However, the perceived effectiveness on the job was lower, which highlights the importance of addressing design barriers to optimize the integration of exoskeletons into specific work environments and aligning them with the wearer’s expectations of improving job performance. Due to the non-repetitive, dynamic nature of EMS work, designs that allow for more mobility must be coupled with guidelines for task-specific exoskeleton usefulness before widespread adoption becomes a possibility. Through future research and design, LBEs can be developed to meet the mobility demands of EMTs while offering support during risky lifting situations.
