Presentation
HE6 - Characterizing Physical Strain in Non-Routinized Clinical Work Through Observation: An Example of Oral Healthcare Providers
DescriptionBackground: Measurement of physical strain is essential to evaluate the risk of developing work-related musculoskeletal injuries. According to a recent survey of ergonomic practitioners, the Strain Index is one of the most commonly used assessments in the field. The Strain Index is a job analysis tool that quantifies the risk of developing distal upper extremity musculoskeletal injuries based on a combination of physical exposure variables such as exertion force, posture, and duration of work. Despite its prevalence in ergonomics practice, applying the Strain Index has been limited to manufacturing jobs with cyclic and predictable physical and behavioral patterns. The quantification of exertion force, posture, and duration is substantially more challenging in clinical and hospital-based environments where the work patterns are non-linear and unpredictable.
Purpose: We propose a modified method to characterize physical exertion in non-routinized clinical work through direct observations using the Strain Index assessment.
Data Source: We use dental hygiene work as an exemplar to illustrate the process of adapting and validating the Strain Index assessment. We selected dental hygiene work because it is characterized by non-routine and unpredictable work patterns that have led to a high prevalence of developing upper-extremity musculoskeletal injuries among dental hygienists. Video recordings and live observations were conducted with students enrolled in two dental hygiene bachelor’s degree programs while they provided one-on-one services during clinical rotations. We recorded videos using three GoPro cameras arranged in orthogonal views. One researcher conducted live observations, using a 15-minute interval sampling method, to estimate wrist angles and identify exertion force patterns while the participants performed dental tasks. Participants rated the intensity of exertions on a Borg CR-10 perceived exertion scale immediately following the observation sessions.
Methods and Results: The method adaptation and validation process occurred in two phases. In phase 1, we modified the definition of exertion in the Strain Index as the direct and continuous application of instruments with similar intensity, frequency, and wrist posture until a rest break of at least 15 seconds. This definition accounts for variabilities in force and posture by observing apparent and distinct changes in work patterns instead of every single movement of the hands, which improves the time efficiency and accuracy of the Strain Index in non-routinized work. Next, we created categories for common exertion force and wrist postures found in dental hygiene work with an expert panel of dental hygiene educators and ergonomic specialists. After two rounds of reliability testing, the expert panel yielded nearly 90% agreement on 5 categories of exertion force patterns (light, moderate, heavy, ultrasonic, and no scaling) and 3 categories of wrist postures (flexion, neutral, extension). These exertion and posture categories help ergonomists to conveniently administer the Strain Index through observations. To further assist with the calculation process of the Strain Index, we calculated the average exertion force (Borg CR-10 scale) and wrist angle for each category based on the video and live observational data. Estimation of the common exertion force incorporated duty cycles (i.e., percentage duration of an exertion) to account for brief pauses or breaks in activity less than 15 seconds to make the instrument coding process more efficient.
In the second phase, we calculated the Composite Strain Index scores on 5 randomly selected video observations using our modified method and compared the results to two alternative calculation methods that approximate more to the original Strain Index sampling method. Our modified method results ranged from 7.7 to 13.6 and two videos exceeded the hazardous thresholds of 10 points while the remaining three were classified as safe. In contrast, the five Strain Index scores calculated using the original sampling method were all above 30. These high scores represent the inflated exertion frequency (>50 efforts per minute) based on the original definition of exertion. To further validate our results, we completed a third method that calculated the Strain Index scores based on raw Borg-CR ratings instead of incorporating duty cycles in the exertion. The third method yielded results similar to our modified method: only two videos exceeded 10 points. The notable difference was that the third method took twice the time to complete compared to our modified method.
Purpose: We propose a modified method to characterize physical exertion in non-routinized clinical work through direct observations using the Strain Index assessment.
Data Source: We use dental hygiene work as an exemplar to illustrate the process of adapting and validating the Strain Index assessment. We selected dental hygiene work because it is characterized by non-routine and unpredictable work patterns that have led to a high prevalence of developing upper-extremity musculoskeletal injuries among dental hygienists. Video recordings and live observations were conducted with students enrolled in two dental hygiene bachelor’s degree programs while they provided one-on-one services during clinical rotations. We recorded videos using three GoPro cameras arranged in orthogonal views. One researcher conducted live observations, using a 15-minute interval sampling method, to estimate wrist angles and identify exertion force patterns while the participants performed dental tasks. Participants rated the intensity of exertions on a Borg CR-10 perceived exertion scale immediately following the observation sessions.
Methods and Results: The method adaptation and validation process occurred in two phases. In phase 1, we modified the definition of exertion in the Strain Index as the direct and continuous application of instruments with similar intensity, frequency, and wrist posture until a rest break of at least 15 seconds. This definition accounts for variabilities in force and posture by observing apparent and distinct changes in work patterns instead of every single movement of the hands, which improves the time efficiency and accuracy of the Strain Index in non-routinized work. Next, we created categories for common exertion force and wrist postures found in dental hygiene work with an expert panel of dental hygiene educators and ergonomic specialists. After two rounds of reliability testing, the expert panel yielded nearly 90% agreement on 5 categories of exertion force patterns (light, moderate, heavy, ultrasonic, and no scaling) and 3 categories of wrist postures (flexion, neutral, extension). These exertion and posture categories help ergonomists to conveniently administer the Strain Index through observations. To further assist with the calculation process of the Strain Index, we calculated the average exertion force (Borg CR-10 scale) and wrist angle for each category based on the video and live observational data. Estimation of the common exertion force incorporated duty cycles (i.e., percentage duration of an exertion) to account for brief pauses or breaks in activity less than 15 seconds to make the instrument coding process more efficient.
In the second phase, we calculated the Composite Strain Index scores on 5 randomly selected video observations using our modified method and compared the results to two alternative calculation methods that approximate more to the original Strain Index sampling method. Our modified method results ranged from 7.7 to 13.6 and two videos exceeded the hazardous thresholds of 10 points while the remaining three were classified as safe. In contrast, the five Strain Index scores calculated using the original sampling method were all above 30. These high scores represent the inflated exertion frequency (>50 efforts per minute) based on the original definition of exertion. To further validate our results, we completed a third method that calculated the Strain Index scores based on raw Borg-CR ratings instead of incorporating duty cycles in the exertion. The third method yielded results similar to our modified method: only two videos exceeded 10 points. The notable difference was that the third method took twice the time to complete compared to our modified method.
Event Type
Poster Presentation
TimeMonday, March 254:45pm - 6:15pm CDT
LocationSalon C
Digital Health
Simulation and Education
Hospital Environments
Medical and Drug Delivery Devices
Patient Safety Research and Initiatives