.................................................................................................... more .................................................................................................................. ii Acknowledgments................................................................................................... v Vita ......................................................................................................................... vi Publications ............................................................................................................ vi Fields of Study ....................................................................................................... vi Table of
Objective The objective of this systematic review was to investigate the potential link between c... more Objective The objective of this systematic review was to investigate the potential link between cognitive dissonance or its related constructs (emotional dissonance, emotional labor) and musculoskeletal disorders. Background The etiology of musculoskeletal disorders is complex, as pain arises from complex interactions among physical, social, and psychological stressors. It is possible that the psychological factor of cognitive dissonance may contribute to the etiology and/or maintenance of musculoskeletal disorders. Method MEDLINE, APA PsycInfo, and CINAHL Plus databases were searched for studies investigating cognitive dissonance or its related constructs as exposure(s) of interest and outcomes related to physical health (including, but not limited to, musculoskeletal pain). Risk of bias was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS) tool. Results The literature search yielded 7 studies eligible for inclusion. None of the included studies investigated cognitive dissonance directly but instead investigated dissonance-related constructs of emotional dissonance and emotional labor, in which a mismatch between required and felt emotions might elicit a psychological response consistent with the cognitive dissonance state. Moderate effect sizes between dissonance-related constructs and musculoskeletal disorders were noted (OR 1.25–2.22). Conclusion There is likely a relationship between the two factors studied. However, as the included studies were cross-sectional in nature, a causal relationship between cognitive dissonance-related constructs and musculoskeletal disorders cannot be inferred. Therefore, future study proposing and validating a causal pathway between these variables is warranted. Application Cognitive dissonance and its related constructs may serve as risk factors for musculoskeletal disorders that have not been considered previously.
.................................................................................................... more .................................................................................................................. ii Acknowledgments................................................................................................... v Vita ......................................................................................................................... vi Publications ............................................................................................................ vi Fields of Study ....................................................................................................... vi Table of
This study investigated the effects of using a single-axis force gauge for push/pull force measur... more This study investigated the effects of using a single-axis force gauge for push/pull force measurement on kinetic/ kinematic measures associated with the exertion and assessed agreement between forces recorded from two technologies (single-axis gauge, three-dimensional hand transducer) and various test conditions via intraclass correlations. Independent measures included exertion type (push, pull, turn), test condition (natural/cart alone, using force gauge at fast/slow/self-selected paces), and cart weight (light, heavy). Dependent measures included mean angles of force application, peak forces recorded from both technologies, and cart velocity. Excellent agreement was observed between technologies (ICC ¼ 0.998). Likewise, peak forces using the single-axis gauge at the fast pace agreed best with the natural test condition (ICC ¼ 0.631). Forces should be measured using a faster initial acceleration and sustained velocity than is prescribed by the current standard if they are to accurately approximate forces relative to existing push/pull guidelines. Future work should also develop recommendations for measuring turning forces.
Human Factors: The Journal of the Human Factors and Ergonomics Society
Objective The objective of this systematic review was to investigate the potential link between c... more Objective The objective of this systematic review was to investigate the potential link between cognitive dissonance or its related constructs (emotional dissonance, emotional labor) and musculoskeletal disorders. Background The etiology of musculoskeletal disorders is complex, as pain arises from complex interactions among physical, social, and psychological stressors. It is possible that the psychological factor of cognitive dissonance may contribute to the etiology and/or maintenance of musculoskeletal disorders. Method MEDLINE, APA PsycInfo, and CINAHL Plus databases were searched for studies investigating cognitive dissonance or its related constructs as exposure(s) of interest and outcomes related to physical health (including, but not limited to, musculoskeletal pain). Risk of bias was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS) tool. Results The literature search yielded 7 studies eligible for inclusion. None of the included studies investigated cogn...
The objective of this study was to test the feasibility of using a pair of wearable inertial meas... more The objective of this study was to test the feasibility of using a pair of wearable inertial measurement unit (IMU) sensors to accurately capture dynamic joint motion data during simulated occupational conditions. Eleven subjects (5 males and 6 females) performed repetitive neck, low-back, and shoulder motions simulating low- and high-difficulty occupational tasks in a laboratory setting. Kinematics for each of the 3 joints were measured via IMU sensors in addition to a “gold standard” passive marker optical motion capture system. The IMU accuracy was benchmarked relative to the optical motion capture system, and IMU sensitivity to low- and high-difficulty tasks was evaluated. The accuracy of the IMU sensors was found to be very good on average, but significant positional drift was observed in some trials. In addition, IMU measurements were shown to be sensitive to differences in task difficulty in all 3 joints (P
Journal of safety, health and environmental research
Work-related musculoskeletal disorder (WMSD) prevention measures have been studied in great depth... more Work-related musculoskeletal disorder (WMSD) prevention measures have been studied in great depth throughout various industries. While the nature and causes of these disorders have been characterized in many industries, WMSDs occurring in the U.S. mining sector have not been characterized for several years. In this report, MSHA accident/injury/illness data from 2009 to 2013 were characterized to determine the most frequently reported WMSDs in the U.S. mining sector. WMSDs were most frequently reported in workers with less than 5 years or more than 20 years of mining experience. The number of days lost from work was the highest for shoulder and knee injuries and was found to increase with worker age. Underground and surface coal, surface stone and stone processing plants experienced the greatest number of WMSDs over the period studied. WMSDs were most commonly caused by an employee suffering from an overexertion, falls or being struck by an object while performing materials handling,...
Industrial passive low-back exoskeletons have gained recent attention as ergonomic interventions ... more Industrial passive low-back exoskeletons have gained recent attention as ergonomic interventions to manual handling tasks. This research utilized a two-armed experimental approach (single vs dual-task paradigms) to quantify neural and biomechanical tradeoffs associated with short-term human-exoskeleton interaction (HEI) during asymmetrical lifting in twelve healthy adults balanced by gender. A dynamic, electromyography-assisted spine model was employed that indicated statistical, but marginal, biomechanical benefits of the tested exoskeleton, which diminished with the introduction of the cognitive dual-task. Using Near Infrared Spectroscopy (fNIRS)-based brain connectivity analyses, we found that the tested exoskeleton imposed greater neurocognitive and motor adaptation efforts by engaging action monitoring and error processing brain networks. Collectively, these findings indicate that a wearer's biomechanical response to increased cognitive demands in the workplace may offset the mechanical advantages of exoskeletons. We also demonstrate the utility of ambulatory fNIRS to capture the neural cost of HEI without the need for elaborate dual-task manipulations.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2017
Background: In an attempt to reduce heavy lifting exposures, the manual materials handling burden... more Background: In an attempt to reduce heavy lifting exposures, the manual materials handling burden has shifted towards pushing and pulling. Pushing and pulling may pose a biomechanical risk due to excessive loads placed onto the lumbar spine, particularly in anterior/posterior (A/P) shear (Knapik and Marras 2009). The only risk limits available in the scientific literature for pushing and pulling were psychophysically-determined, relying on the assumption that subjective perception of an individual’s maximum acceptable external forces corresponds to biomechanical tolerance (Snook and Ciriello 1991). However, individuals are unlikely able to sense biomechanical loading on critical tissues in the spine due to the lack of nociceptors in the intervertebral disc (Adams et al. 1996). As such, the objective of this study was to create a set of biomechanically-determined risk limits for occupational pushing and pulling that are protective of the low back. Methods: Sixty-two subjects (31 male...
Key Points Question How does posttraumatic stress disorder (PTSD) change during a 1-year period i... more Key Points Question How does posttraumatic stress disorder (PTSD) change during a 1-year period in female refugees who survived mass atrocities, and what factors are associated with PTSD course? Findings This cohort study with 116 female refugee survivors of captivity and genocide found high PTSD severity 2 years after resettlement in Germany with no significant change 1 year later. Factors associated with severe PTSD were earlier symptoms of intrusions and longer time spent in traumatic situations, whereas strengthening in faith and social relationships were associated with symptom relief over time. Meaning This study suggests that female refugee survivors of genocide and captivity are at high risk for severe and chronic PTSD beyond the initial years of resettlement.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2020
In 2018, low back injuries accounted for more than 264 million lost work days in the United State... more In 2018, low back injuries accounted for more than 264 million lost work days in the United States. The majority of such low back injury incidents are a result of overexertion and repetitive twisting motions, especially during asymmetrical manual material handling (MMH; Waddell & Burton, 2001). Semi-automated solutions, such as using passive low-back exoskeletons, have gained attention in the manufacturing sector. While low back passive exoskeletons have shown to reduce spinal loads (Lazzaroni, Toxiri, Ortiz, De Momi, & Caldwell, 2018), they also introduce new risks to the workplaces, such as cognitive overload, which have not been adequately assessed during both exoskeleton design and evaluation processes (Stirling et al., 2020). Therefore, a systematic efficiency evaluation tool, neural efficiency, which examines exoskeleton performance (i.e., biomechanics outcomes) in conjunction with the neurophysiological cost of maintaining that performance (i.e., neural effort) (Curtin & Ayaz, 2019), was utilized to better understand and quantify the impact of an industrial passive low-back exoskeleton on the users during a repetitive MMH task . In this study, twelve volunteers performed a simulated asymmetrical MMH task with and without wearing a passive low-back exoskeleton, Laevo (Laevo, the Netherland), on two separate days. We assessed compression and shear loads on the L3L4 and L5S1 sections of the lumbar spine using an EMGassisted spine model (Weston, Alizadeh, Knapik, Wang, & Marras, 2018). We also measured neural effort using a 20channel ambulatory functional near-infrared spectroscopy (fNIRS) system, NIRSport2 (NIRx Medical Technologies, NY, USA). Multiple physical and cognitive task-related brain regions were monitored, These regions included the dorsolateral prefrontal cortex (dlPFC) which is correlated with cognitive workload (McKendrick, Mehta, Ayaz, Scheldrup, & Parasuraman, 2017), supplementary motor area (SMA) and premotor cortex (PMC) which are both in charge of motor planning (Saleh et al., 2018). Peak oxygenated hemoglobin (HbO) levels were obtained from each region. Additionally, corresponding neural efficiency metrics were calculated based on the normalized neural effort and biomechanical load data (Curtin & Ayaz, 2019). A repeated measure 2 Condition (control and exoskeleton) x 2 Phase (early: first 10-minute work and late: last 10-minute work) Analysis of Variance (ANOVA), with a significance level of 0.05, were used to assess their main and interactive effects on individual biomechanical and neural measures, as well as the integrated neural efficiency measures in each brain region. We found that traditional biomechanical and neural measures were unable to capture the dynamic changes in human-exoskeleton interactions over the course of the 30minute MMH task. However, the neural efficiency metrics showed that the human-exoskeleton interaction was efficient, demanding lower neural effort from motor planning regions of the brain while maintaining biomechanical load. However, the tested device was found to burden the user cognitively, as indicated by lower neural efficiency in the cognition-related brain regions, which indicates poor cognitive fit of the exoskeleton design. Our findings highlight the promise of the neural efficiency metric in systematically monitoring neurocognitive load during human-exoskeleton interaction. The results will also facilitate future work that can target continuous and/or real-time tracking of human-exoskeleton interaction, which may contribute to the development of adaptive exoskeleton control algorithms.
The objective of this study was to evaluate three passive upper-extremity exoskeletons relative t... more The objective of this study was to evaluate three passive upper-extremity exoskeletons relative to a control condition. Twelve subjects performed an hour-long, simulated occupational task in a laboratory setting. Independent measures of exoskeleton, exertion height (overhead, head height), time, and their interactions were assessed. Dependent measures included changes in tissue oxygenation (DTSI) in the anterior deltoid and middle trapezius, peak resultant lumbar spine loading, and subjective discomfort in various body regions. A statistically significant reduction in DTSI between exoskeleton and control was only observed in one instance. Additionally, neither increases in spinal loading nor increases in subjective discomfort ratings were observed for any of the exoskeletons. Ultimately, the exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing to the subjects, denoted by low DTSI values across conditions. Results may vary for tasks requiring constant arm elevation or higher force demands.
The objectives of this study were to quantify loads imposed upon the lumbar spine while lifting/l... more The objectives of this study were to quantify loads imposed upon the lumbar spine while lifting/lowering with one versus two hands and to create guidelines for one-handed lifting/lowering that are protective of the lower back. Thirty subjects (15 male, 15 female) performed oneand two-handed exertions in a laboratory, lifting from/lowering to 18 lift origins/destinations using medicine balls of varying masses. An electromyography-assisted model predicted peak spinal loads, which were related to tissue tolerance limits to create recommended weight limits. Compared to two-handed exertions, one-handed exertions resulted in decreased spinal compression and A/P shear loading (p < 0.001) but increased lateral shear (p < 0.001). Effects were likely driven by altered moment exposures attributable to altered torso kinematics. Differences between spinal loads for one-versus two-handed exertions were influenced by asymmetry (p < 0.001) and amplified at lower lift origin/destination heights, lower object masses and larger horizontal distances between the body and the load (p < 0.001).
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2019
Background: Lifting at work remains one of the most highly studied potential risk factors for low... more Background: Lifting at work remains one of the most highly studied potential risk factors for low back disorders, but most of the studies that have been conducted on this topic focus on lifting scenarios in which two hands are used to lift the weight. Few investigations have examined one-handed lifting scenarios, as might be observed when lifting objects from industrial storage bins or stocking products onto shelves. Moreover, there remains a need to re-examine one versus two-handed lifting scenarios utilizing a more advanced and accurate biomechanical model than was used previously (Ferguson et al., 2002; Kingma and van Dieen, 2004; Marras and Davis, 1998). The objective of this study was to quantify biomechanical loads imposed upon the lumbar spine during one-handed lifting versus two-handed lifting, specifically in relation to any interaction effects present between the number of hands used to perform the lift and external lifting conditions like the lift origin or object weight....
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2019
Firefighters and EMS providers continue to be challenged when lifting heavy patients in their hom... more Firefighters and EMS providers continue to be challenged when lifting heavy patients in their homes. This study investigated the biomechanical efficacy of four devices that could be used by two-person teams when lifting patients from the floor, from a reclining chair, or from a Simulated Inflatable Seat at chair height. Fourteen firefighter-paramedics, working in two-person teams, were instrumented with motion capture and electromyographic sensors. The Binder LiftTM and the Simple Strap were used to lift patient actors, and were compared to current lifting methods. Postural data and the peak dynamic spine shear forces at the L5/S1 level were reduced when using the Simple Strap, the Binder Lift, and the Simulated Inflatable Seat. In summary, each of these devices has been shown to have biomechanical support for their use by EMS providers.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2019
Background: Lifting in confined vertical space is observed across several industries, including a... more Background: Lifting in confined vertical space is observed across several industries, including airline baggage handling, mining, construction, maintenance, and shipbuilding. However, only a few studies have investigated confined space lifting scenarios with biomechanical methods (Gallagher et al., 1988; Stalhammar et al., 1986), and fewer have quantified biomechanical loads on the intervertebral discs of the lumbar spine while lifting in confined vertical spaces using a biomechanical model (Gallagher et al., 1994; Middelton et al., 2016; Splittstoesser et al., 2007). The objective of this study was to quantify spinal loads for kneeling and sitting lifting styles in confined vertical space. This was accomplished via the replication of the baggage compartment of a narrow-bodied aircraft in a laboratory. Methods: Ten males performed airline baggage handling tasks for this study. A fully balanced design was implemented, and independent variables included lifting style (3), exertion typ...
The objective of this study was to investigate biomechanical loads on the lumbar spine as a funct... more The objective of this study was to investigate biomechanical loads on the lumbar spine as a function of working in a confined vertical space, consistent with baggage handling inside the baggage compartment of an airplane. Ten male subjects performed baggage handling tasks using confined (kneeling, sitting) and unconfined (stooping) lifting styles. Dependent measures of torso flexion and three-dimensional spinal loads were assessed with an electromyography-driven biomechanical model. Lifting exertions typical to airline baggage handling posed significant risk to the lumbar spine, regardless of lifting style. Statistically significant differences attributable to lift style (stooping, kneeling, sitting) were not observed for peak compressive, lateral shear, or resultant spinal loads, but lifting while kneeling decreased anterior/posterior (A/P) shear spinal loads relative to stooping (p ¼ 0.02). Collectively, kneeling offers the greatest benefit when lifting in confined spaces because of the ability to keep the torso upright, subsequently reducing shear forces on the lumbar spine.
.................................................................................................... more .................................................................................................................. ii Acknowledgments................................................................................................... v Vita ......................................................................................................................... vi Publications ............................................................................................................ vi Fields of Study ....................................................................................................... vi Table of
Objective The objective of this systematic review was to investigate the potential link between c... more Objective The objective of this systematic review was to investigate the potential link between cognitive dissonance or its related constructs (emotional dissonance, emotional labor) and musculoskeletal disorders. Background The etiology of musculoskeletal disorders is complex, as pain arises from complex interactions among physical, social, and psychological stressors. It is possible that the psychological factor of cognitive dissonance may contribute to the etiology and/or maintenance of musculoskeletal disorders. Method MEDLINE, APA PsycInfo, and CINAHL Plus databases were searched for studies investigating cognitive dissonance or its related constructs as exposure(s) of interest and outcomes related to physical health (including, but not limited to, musculoskeletal pain). Risk of bias was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS) tool. Results The literature search yielded 7 studies eligible for inclusion. None of the included studies investigated cognitive dissonance directly but instead investigated dissonance-related constructs of emotional dissonance and emotional labor, in which a mismatch between required and felt emotions might elicit a psychological response consistent with the cognitive dissonance state. Moderate effect sizes between dissonance-related constructs and musculoskeletal disorders were noted (OR 1.25–2.22). Conclusion There is likely a relationship between the two factors studied. However, as the included studies were cross-sectional in nature, a causal relationship between cognitive dissonance-related constructs and musculoskeletal disorders cannot be inferred. Therefore, future study proposing and validating a causal pathway between these variables is warranted. Application Cognitive dissonance and its related constructs may serve as risk factors for musculoskeletal disorders that have not been considered previously.
.................................................................................................... more .................................................................................................................. ii Acknowledgments................................................................................................... v Vita ......................................................................................................................... vi Publications ............................................................................................................ vi Fields of Study ....................................................................................................... vi Table of
This study investigated the effects of using a single-axis force gauge for push/pull force measur... more This study investigated the effects of using a single-axis force gauge for push/pull force measurement on kinetic/ kinematic measures associated with the exertion and assessed agreement between forces recorded from two technologies (single-axis gauge, three-dimensional hand transducer) and various test conditions via intraclass correlations. Independent measures included exertion type (push, pull, turn), test condition (natural/cart alone, using force gauge at fast/slow/self-selected paces), and cart weight (light, heavy). Dependent measures included mean angles of force application, peak forces recorded from both technologies, and cart velocity. Excellent agreement was observed between technologies (ICC ¼ 0.998). Likewise, peak forces using the single-axis gauge at the fast pace agreed best with the natural test condition (ICC ¼ 0.631). Forces should be measured using a faster initial acceleration and sustained velocity than is prescribed by the current standard if they are to accurately approximate forces relative to existing push/pull guidelines. Future work should also develop recommendations for measuring turning forces.
Human Factors: The Journal of the Human Factors and Ergonomics Society
Objective The objective of this systematic review was to investigate the potential link between c... more Objective The objective of this systematic review was to investigate the potential link between cognitive dissonance or its related constructs (emotional dissonance, emotional labor) and musculoskeletal disorders. Background The etiology of musculoskeletal disorders is complex, as pain arises from complex interactions among physical, social, and psychological stressors. It is possible that the psychological factor of cognitive dissonance may contribute to the etiology and/or maintenance of musculoskeletal disorders. Method MEDLINE, APA PsycInfo, and CINAHL Plus databases were searched for studies investigating cognitive dissonance or its related constructs as exposure(s) of interest and outcomes related to physical health (including, but not limited to, musculoskeletal pain). Risk of bias was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS) tool. Results The literature search yielded 7 studies eligible for inclusion. None of the included studies investigated cogn...
The objective of this study was to test the feasibility of using a pair of wearable inertial meas... more The objective of this study was to test the feasibility of using a pair of wearable inertial measurement unit (IMU) sensors to accurately capture dynamic joint motion data during simulated occupational conditions. Eleven subjects (5 males and 6 females) performed repetitive neck, low-back, and shoulder motions simulating low- and high-difficulty occupational tasks in a laboratory setting. Kinematics for each of the 3 joints were measured via IMU sensors in addition to a “gold standard” passive marker optical motion capture system. The IMU accuracy was benchmarked relative to the optical motion capture system, and IMU sensitivity to low- and high-difficulty tasks was evaluated. The accuracy of the IMU sensors was found to be very good on average, but significant positional drift was observed in some trials. In addition, IMU measurements were shown to be sensitive to differences in task difficulty in all 3 joints (P
Journal of safety, health and environmental research
Work-related musculoskeletal disorder (WMSD) prevention measures have been studied in great depth... more Work-related musculoskeletal disorder (WMSD) prevention measures have been studied in great depth throughout various industries. While the nature and causes of these disorders have been characterized in many industries, WMSDs occurring in the U.S. mining sector have not been characterized for several years. In this report, MSHA accident/injury/illness data from 2009 to 2013 were characterized to determine the most frequently reported WMSDs in the U.S. mining sector. WMSDs were most frequently reported in workers with less than 5 years or more than 20 years of mining experience. The number of days lost from work was the highest for shoulder and knee injuries and was found to increase with worker age. Underground and surface coal, surface stone and stone processing plants experienced the greatest number of WMSDs over the period studied. WMSDs were most commonly caused by an employee suffering from an overexertion, falls or being struck by an object while performing materials handling,...
Industrial passive low-back exoskeletons have gained recent attention as ergonomic interventions ... more Industrial passive low-back exoskeletons have gained recent attention as ergonomic interventions to manual handling tasks. This research utilized a two-armed experimental approach (single vs dual-task paradigms) to quantify neural and biomechanical tradeoffs associated with short-term human-exoskeleton interaction (HEI) during asymmetrical lifting in twelve healthy adults balanced by gender. A dynamic, electromyography-assisted spine model was employed that indicated statistical, but marginal, biomechanical benefits of the tested exoskeleton, which diminished with the introduction of the cognitive dual-task. Using Near Infrared Spectroscopy (fNIRS)-based brain connectivity analyses, we found that the tested exoskeleton imposed greater neurocognitive and motor adaptation efforts by engaging action monitoring and error processing brain networks. Collectively, these findings indicate that a wearer's biomechanical response to increased cognitive demands in the workplace may offset the mechanical advantages of exoskeletons. We also demonstrate the utility of ambulatory fNIRS to capture the neural cost of HEI without the need for elaborate dual-task manipulations.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2017
Background: In an attempt to reduce heavy lifting exposures, the manual materials handling burden... more Background: In an attempt to reduce heavy lifting exposures, the manual materials handling burden has shifted towards pushing and pulling. Pushing and pulling may pose a biomechanical risk due to excessive loads placed onto the lumbar spine, particularly in anterior/posterior (A/P) shear (Knapik and Marras 2009). The only risk limits available in the scientific literature for pushing and pulling were psychophysically-determined, relying on the assumption that subjective perception of an individual’s maximum acceptable external forces corresponds to biomechanical tolerance (Snook and Ciriello 1991). However, individuals are unlikely able to sense biomechanical loading on critical tissues in the spine due to the lack of nociceptors in the intervertebral disc (Adams et al. 1996). As such, the objective of this study was to create a set of biomechanically-determined risk limits for occupational pushing and pulling that are protective of the low back. Methods: Sixty-two subjects (31 male...
Key Points Question How does posttraumatic stress disorder (PTSD) change during a 1-year period i... more Key Points Question How does posttraumatic stress disorder (PTSD) change during a 1-year period in female refugees who survived mass atrocities, and what factors are associated with PTSD course? Findings This cohort study with 116 female refugee survivors of captivity and genocide found high PTSD severity 2 years after resettlement in Germany with no significant change 1 year later. Factors associated with severe PTSD were earlier symptoms of intrusions and longer time spent in traumatic situations, whereas strengthening in faith and social relationships were associated with symptom relief over time. Meaning This study suggests that female refugee survivors of genocide and captivity are at high risk for severe and chronic PTSD beyond the initial years of resettlement.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2020
In 2018, low back injuries accounted for more than 264 million lost work days in the United State... more In 2018, low back injuries accounted for more than 264 million lost work days in the United States. The majority of such low back injury incidents are a result of overexertion and repetitive twisting motions, especially during asymmetrical manual material handling (MMH; Waddell & Burton, 2001). Semi-automated solutions, such as using passive low-back exoskeletons, have gained attention in the manufacturing sector. While low back passive exoskeletons have shown to reduce spinal loads (Lazzaroni, Toxiri, Ortiz, De Momi, & Caldwell, 2018), they also introduce new risks to the workplaces, such as cognitive overload, which have not been adequately assessed during both exoskeleton design and evaluation processes (Stirling et al., 2020). Therefore, a systematic efficiency evaluation tool, neural efficiency, which examines exoskeleton performance (i.e., biomechanics outcomes) in conjunction with the neurophysiological cost of maintaining that performance (i.e., neural effort) (Curtin & Ayaz, 2019), was utilized to better understand and quantify the impact of an industrial passive low-back exoskeleton on the users during a repetitive MMH task . In this study, twelve volunteers performed a simulated asymmetrical MMH task with and without wearing a passive low-back exoskeleton, Laevo (Laevo, the Netherland), on two separate days. We assessed compression and shear loads on the L3L4 and L5S1 sections of the lumbar spine using an EMGassisted spine model (Weston, Alizadeh, Knapik, Wang, & Marras, 2018). We also measured neural effort using a 20channel ambulatory functional near-infrared spectroscopy (fNIRS) system, NIRSport2 (NIRx Medical Technologies, NY, USA). Multiple physical and cognitive task-related brain regions were monitored, These regions included the dorsolateral prefrontal cortex (dlPFC) which is correlated with cognitive workload (McKendrick, Mehta, Ayaz, Scheldrup, & Parasuraman, 2017), supplementary motor area (SMA) and premotor cortex (PMC) which are both in charge of motor planning (Saleh et al., 2018). Peak oxygenated hemoglobin (HbO) levels were obtained from each region. Additionally, corresponding neural efficiency metrics were calculated based on the normalized neural effort and biomechanical load data (Curtin & Ayaz, 2019). A repeated measure 2 Condition (control and exoskeleton) x 2 Phase (early: first 10-minute work and late: last 10-minute work) Analysis of Variance (ANOVA), with a significance level of 0.05, were used to assess their main and interactive effects on individual biomechanical and neural measures, as well as the integrated neural efficiency measures in each brain region. We found that traditional biomechanical and neural measures were unable to capture the dynamic changes in human-exoskeleton interactions over the course of the 30minute MMH task. However, the neural efficiency metrics showed that the human-exoskeleton interaction was efficient, demanding lower neural effort from motor planning regions of the brain while maintaining biomechanical load. However, the tested device was found to burden the user cognitively, as indicated by lower neural efficiency in the cognition-related brain regions, which indicates poor cognitive fit of the exoskeleton design. Our findings highlight the promise of the neural efficiency metric in systematically monitoring neurocognitive load during human-exoskeleton interaction. The results will also facilitate future work that can target continuous and/or real-time tracking of human-exoskeleton interaction, which may contribute to the development of adaptive exoskeleton control algorithms.
The objective of this study was to evaluate three passive upper-extremity exoskeletons relative t... more The objective of this study was to evaluate three passive upper-extremity exoskeletons relative to a control condition. Twelve subjects performed an hour-long, simulated occupational task in a laboratory setting. Independent measures of exoskeleton, exertion height (overhead, head height), time, and their interactions were assessed. Dependent measures included changes in tissue oxygenation (DTSI) in the anterior deltoid and middle trapezius, peak resultant lumbar spine loading, and subjective discomfort in various body regions. A statistically significant reduction in DTSI between exoskeleton and control was only observed in one instance. Additionally, neither increases in spinal loading nor increases in subjective discomfort ratings were observed for any of the exoskeletons. Ultimately, the exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing to the subjects, denoted by low DTSI values across conditions. Results may vary for tasks requiring constant arm elevation or higher force demands.
The objectives of this study were to quantify loads imposed upon the lumbar spine while lifting/l... more The objectives of this study were to quantify loads imposed upon the lumbar spine while lifting/lowering with one versus two hands and to create guidelines for one-handed lifting/lowering that are protective of the lower back. Thirty subjects (15 male, 15 female) performed oneand two-handed exertions in a laboratory, lifting from/lowering to 18 lift origins/destinations using medicine balls of varying masses. An electromyography-assisted model predicted peak spinal loads, which were related to tissue tolerance limits to create recommended weight limits. Compared to two-handed exertions, one-handed exertions resulted in decreased spinal compression and A/P shear loading (p < 0.001) but increased lateral shear (p < 0.001). Effects were likely driven by altered moment exposures attributable to altered torso kinematics. Differences between spinal loads for one-versus two-handed exertions were influenced by asymmetry (p < 0.001) and amplified at lower lift origin/destination heights, lower object masses and larger horizontal distances between the body and the load (p < 0.001).
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2019
Background: Lifting at work remains one of the most highly studied potential risk factors for low... more Background: Lifting at work remains one of the most highly studied potential risk factors for low back disorders, but most of the studies that have been conducted on this topic focus on lifting scenarios in which two hands are used to lift the weight. Few investigations have examined one-handed lifting scenarios, as might be observed when lifting objects from industrial storage bins or stocking products onto shelves. Moreover, there remains a need to re-examine one versus two-handed lifting scenarios utilizing a more advanced and accurate biomechanical model than was used previously (Ferguson et al., 2002; Kingma and van Dieen, 2004; Marras and Davis, 1998). The objective of this study was to quantify biomechanical loads imposed upon the lumbar spine during one-handed lifting versus two-handed lifting, specifically in relation to any interaction effects present between the number of hands used to perform the lift and external lifting conditions like the lift origin or object weight....
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2019
Firefighters and EMS providers continue to be challenged when lifting heavy patients in their hom... more Firefighters and EMS providers continue to be challenged when lifting heavy patients in their homes. This study investigated the biomechanical efficacy of four devices that could be used by two-person teams when lifting patients from the floor, from a reclining chair, or from a Simulated Inflatable Seat at chair height. Fourteen firefighter-paramedics, working in two-person teams, were instrumented with motion capture and electromyographic sensors. The Binder LiftTM and the Simple Strap were used to lift patient actors, and were compared to current lifting methods. Postural data and the peak dynamic spine shear forces at the L5/S1 level were reduced when using the Simple Strap, the Binder Lift, and the Simulated Inflatable Seat. In summary, each of these devices has been shown to have biomechanical support for their use by EMS providers.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2019
Background: Lifting in confined vertical space is observed across several industries, including a... more Background: Lifting in confined vertical space is observed across several industries, including airline baggage handling, mining, construction, maintenance, and shipbuilding. However, only a few studies have investigated confined space lifting scenarios with biomechanical methods (Gallagher et al., 1988; Stalhammar et al., 1986), and fewer have quantified biomechanical loads on the intervertebral discs of the lumbar spine while lifting in confined vertical spaces using a biomechanical model (Gallagher et al., 1994; Middelton et al., 2016; Splittstoesser et al., 2007). The objective of this study was to quantify spinal loads for kneeling and sitting lifting styles in confined vertical space. This was accomplished via the replication of the baggage compartment of a narrow-bodied aircraft in a laboratory. Methods: Ten males performed airline baggage handling tasks for this study. A fully balanced design was implemented, and independent variables included lifting style (3), exertion typ...
The objective of this study was to investigate biomechanical loads on the lumbar spine as a funct... more The objective of this study was to investigate biomechanical loads on the lumbar spine as a function of working in a confined vertical space, consistent with baggage handling inside the baggage compartment of an airplane. Ten male subjects performed baggage handling tasks using confined (kneeling, sitting) and unconfined (stooping) lifting styles. Dependent measures of torso flexion and three-dimensional spinal loads were assessed with an electromyography-driven biomechanical model. Lifting exertions typical to airline baggage handling posed significant risk to the lumbar spine, regardless of lifting style. Statistically significant differences attributable to lift style (stooping, kneeling, sitting) were not observed for peak compressive, lateral shear, or resultant spinal loads, but lifting while kneeling decreased anterior/posterior (A/P) shear spinal loads relative to stooping (p ¼ 0.02). Collectively, kneeling offers the greatest benefit when lifting in confined spaces because of the ability to keep the torso upright, subsequently reducing shear forces on the lumbar spine.
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