International Journal of Occupational Safety and Ergonomics Jose, Feb 1, 2009
In this study a multiaxial isokinetic dynamometer was used to measure strength during various upp... more In this study a multiaxial isokinetic dynamometer was used to measure strength during various upper-body isokinetic exertions. Ten male participants performed 7 different upper-body isokinetic exertions. In addition, to evaluate the effect of speed on strength, each participant performed sitting pull exertions at the speed of 0.026, 0.130, and 0.260 m/s. Average isokinetic strength increased from 236.6 +/- 39.1 to 291.8 +/- 65.8 N with the initial increase in speed from 0.026 to 0.130 m/s. The average isokinetic strength decreased to 276.7 +/- 87.2 N with a further increase in speed to 0.260 m/s. The curve between isokinetic strength and speed followed a bell-shaped curve (fitted with the Gaussian function, R(2) = .9). The results of this study could be useful in deciding on the work pace of various manual material handling tasks requiring maximal and/or near maximal exertions.
Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern w... more Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern working population. Epidemiological literature suggests that forceful arm exertions pose an increased risk for shoulder MSD development. The majority of shoulder MSDs involve the glenohumeral joint. The glenohumeral joint is characteristically unstable and stabilized by concavity compression mechanism. In this study a biomechanical model of the shoulder complex was used to examine the concavity compression mechanism. Mechanical loading of the glenohumeral joint during forceful arm exertions was analyzed to quantify the angular position of the resultant muscle force vector in 3D space. The resultant muscle force vectors were almost always directed anteriorly, medially, and inferiorly, independent of the magnitude and the direction of the external force application. The knowledge gained in this study could potentially be used to develop a new assessment method to evaluate the risk of injury...
In this study, the effect of prolonged forward flexion on the recovery process of the reflexive m... more In this study, the effect of prolonged forward flexion on the recovery process of the reflexive muscle activity of the lumbar musculature to its original state is studied using human participants. The behavior of the lower back erector spinae muscle during 20 minutes of forward bending and three hours of recovery was evaluated experimentally using electromyography (EMG) and mathematical modeling. Ten healthy males participated in this study. The EMG of erector-spinae muscle from two different lumbar levels was recorded and expressed as normalized integrated EMG (NIEMG). In general, the average NIEMG values of the erector spinae muscles demonstrated an exponential decrease during the 20-minute loading period. The biexoponential structure, derived from the animal model, did not completely explain the muscle behavior during recovery period. Inclusion of the "intrinsic loading factor" to the biexoponential structure improved the fit of the recovery model to 100%. Most of the r...
International Journal of Occupational Safety and Ergonomics, 2009
In this study a multiaxial isokinetic dynamometer was used to measure strength during various upp... more In this study a multiaxial isokinetic dynamometer was used to measure strength during various upper-body isokinetic exertions. Ten male participants performed 7 different upper-body isokinetic exertions. In addition, to evaluate the effect of speed on strength, each participant performed sitting pull exertions at the speed of 0.026, 0.130, and 0.260 m/s. Average isokinetic strength increased from 236.6 +/- 39.1 to 291.8 +/- 65.8 N with the initial increase in speed from 0.026 to 0.130 m/s. The average isokinetic strength decreased to 276.7 +/- 87.2 N with a further increase in speed to 0.260 m/s. The curve between isokinetic strength and speed followed a bell-shaped curve (fitted with the Gaussian function, R(2) = .9). The results of this study could be useful in deciding on the work pace of various manual material handling tasks requiring maximal and/or near maximal exertions.
Assessment of neuromuscular fatigue is essential for early detection and prevention of risks asso... more Assessment of neuromuscular fatigue is essential for early detection and prevention of risks associated with work-related musculoskeletal disorders. In recent years, discrete wavelet transform (DWT) of surface electromyography (SEMG) has been used to evaluate muscle fatigue, especially during dynamic contractions when the SEMG signal is non-stationary. However, its application to the assessment of work-related neck and shoulder muscle fatigue is not well established. Therefore, the purpose of this study was to establish DWT analysis as a suitable method to conduct quantitative assessment of neck and shoulder muscle fatigue under dynamic repetitive conditions. Ten human participants performed 40min of fatiguing repetitive arm and neck exertions while SEMG data from the upper trapezius and sternocleidomastoid muscles were recorded. The ten of the most commonly used wavelet functions were used to conduct the DWT analysis. Spectral changes estimated using power of wavelet coefficients in the 12-23Hz frequency band showed the highest sensitivity to fatigue induced by the dynamic repetitive exertions. Although most of the wavelet functions tested in this study reasonably demonstrated the expected power trend with fatigue development and recovery, the overall performance of the "Rbio3.1" wavelet in terms of power estimation and statistical significance was better than the remaining nine wavelets.
Sudden unexpected loading has been identified as a risk factor of work-related low back pain (LBP... more Sudden unexpected loading has been identified as a risk factor of work-related low back pain (LBP). This study investigated the effects of different foot placements and load-releasing locations on trunk biomechanics under an unexpected sudden loading event. Fifteen subjects experienced sudden release of a 6.8-kg external load from symmetric or asymmetric directions while maintaining four different foot placements. The results showed that subjects experienced on average 4.1° less trunk flexion, 6.6 Nm less L5/S1 joint moment and 32.0 N less shear force with staggered stance with the right foot forward (the most preferred placement) compared with wide stance (the least preferred placement). Asymmetric load-releasing positions consistently resulted in smaller impacts on trunk biomechanics than symmetric positions. The findings suggest that staggered stance and asymmetric load-holding position can be used as a protective load-handling posture against LBP caused by sudden loading. In a work environment, unexpected sudden loading may cause low back pain (LBP). In this study, we used empirical data to demonstrate how different foot placements and load-releasing locations can be used to mitigate the impact of sudden loading on the spine and to reduce the risk of LBP.
The primary objective of this study was to quantify the effect of dynamic cart pushing exertions ... more The primary objective of this study was to quantify the effect of dynamic cart pushing exertions on the biomechanical loading of shoulder and low back. Ten participants performed cart pushing tasks on flat (0°), 5°, and 10° ramped walkways at 20 kg, 30 kg, and 40 kg weight conditions. An optoelectronic motion capturing system configured with two force plates was used for the kinematic and ground reaction force data collection. The experimental data was modeled using AnyBody modeling system to compute three-dimensional peak reaction forces at the shoulder complex (sternoclavicular, acromioclavicular, and glenohumeral) and low back (lumbosacral) joints. The main effect of walkway gradient and cart weight, and gradient by weight interaction on the biomechanical loading of shoulder complex and low back joints was statistically significant (all p < 0.001). At the lumbosacral joint, negligible loading in the mediolateral direction was observed compared to the anterioposterior and compression directions. Among the shoulder complex joints, the peak reaction forces at the acromioclavicular and glenohumeral joints were comparable and much higher than the sternoclavicular joint. Increased shear loading of the lumbosacral joint, distraction loading of glenohumeral joint and inferosuperior loading of the acromioclavicular joint may contribute to the risk of work-related low back and shoulder musculoskeletal disorder with prolonged and repetitive use of carts.
Http Dx Doi Org 10 1080 00140139 2013 803161, Jun 3, 2013
Lifting tasks performed on uneven ground surfaces are common in outdoor industries. Previous stud... more Lifting tasks performed on uneven ground surfaces are common in outdoor industries. Previous studies have demonstrated that lifting tasks performed on laterally slanted ground surfaces influence lumbar muscle activation and trunk kinematics. In this study, the effect of laterally slanted ground surfaces on the lumbar muscle flexion-relaxation responses was investigated. Fourteen participants performed sagittal plane, trunk flexion-extension tasks on three laterally slanted ground surfaces (0° (flat ground), 15° and 30°), while lumbar muscle activities and trunk kinematics were recorded. Results showed that flexion-relaxation occurred up to 6.2° earlier among ipsilateral lumbar muscles with an increase in laterally slanted ground angle; however, the contralateral side was not affected as much. Our findings suggest that uneven ground alters the lumbar tissue load-sharing mechanism and creates unbalanced lumbar muscle activity, which may increase the risk of low back pain with repeated exposure to lifting on variable surfaces. Uneven ground surfaces are ubiquitous in agriculture, construction, fishing and other outdoor industries. A better understanding of the effects of laterally slanted ground surfaces on the interaction between passive and active lumbar tissues during lifting tasks could provide valuable knowledge in the design of preventive strategies for low back injuries.
Iie Transactions on Occupational Ergonomics and Human Factors, Oct 1, 2013
ABSTRACT Surgical tasks performed using loupes and headlamps were examined to identify exposures ... more ABSTRACT Surgical tasks performed using loupes and headlamps were examined to identify exposures to physical risk factors for work-related musculoskeletal disorders in the neck among microsurgeons. Surgeons who use loupes and headlamps were found to spend extensive time periods working in non-neutral head–neck postures. These postures, and the use of loupes and headlamps, were found to be associated with an increased loading of the cervical spine, which might cumulatively contribute to occupational neck musculoskeletal disorders. To develop effective control strategies, future studies should focus on the impact of design features of loupes (e.g., mount angles, weight, and shape) on head–neck postures during surgical tasks.TECHNICAL ABSTRACT Background: Work-related musculoskeletal disorders in the neck are common among microsurgeons who operate with loupes and headlamps. Published surveys indicate that microsurgeons across many subspecialties believe that loupes contribute to neck musculoskeletal disorders. However, objective data on head–neck posture and cervical loading during surgical tasks performed using loupes and headlamps are currently lacking. Purpose: This study will assess exposures to physical risk factors for neck musculoskeletal disorders during surgical tasks performed using loupes and headlamp. Methods: A field study was performed in operating rooms to measure the head–neck postures commonly used by three ophthalmic plastic surgeons; a subset of microsurgeons. Posture data were used as input to a biomechanical model to estimate cervical spine loading. Results: During nearly 85% of the time spent operating, surgeons adopted asymmetrical head–neck postures characterized by either bending or rotation of >15°, coupled with flexion of >15°. Postures consisting of flexion ≥45°, 15°–30° bending, and 15°–45° rotation produced significantly higher biomechanical loading of the cervical spine compared to near-neutral postures (i.e., flexion, bending and rotation between 0° and 15°). This loading was further exaggerated by the weight of loupes and headlamp. Conclusions: Non-neutral head–neck postures demanded by the dexterous operating tasks performed using loupes and headlamps could be important biomechanical risk factors for cervical musculoskeletal disorders among microsurgeons.
To increase awareness of cervical musculoskeletal disorders (cMSD) in ophthalmic plastic surgeons... more To increase awareness of cervical musculoskeletal disorders (cMSD) in ophthalmic plastic surgeons (OPS) and review strategies for management and prevention. There are objective data that show OPS spend the majority of their time operating in awkward, prolonged, static, asymmetric postures. These postures increase cervical load and cMSD. Loupes and headlamps further increase this cervical loading by 40%. Risk for cMSD is not limited to the operating room. Muscular demands in the anterior deltoid and cervical trapezius are increased in slit lamp biomicroscopy and indirect ophthalmoscopy. Furthermore, the majority of the office visit is spent keyboarding into the electronic medical record which is associated with cMSD. Habitual postural faults result from these cumulative exposures. These must be addressed to prevent further insult and debilitating injury. Successful management requires education in neutral posture, therapeutic exercise, environmental adjustments in the workplace and home, and supported neutral sleep posture. The risks of cMSD in OPS are well established, and nearly 10% of cervical injury will end a career. Neck pain must not be ignored, and experienced professional help is critical. A long-term approach that incorporates exercise, manual therapy, and education is essential for management and prevention.
In this investigation posture restriction caused by back belt is studied. Two-dimensional kinemat... more In this investigation posture restriction caused by back belt is studied. Two-dimensional kinematic data was collected from ten participants using nine marker positions. Angular displacement of nine body angles was compared. Effect of the back belt on the lifting posture was studied using postural index values and kinematic relationship hypothesis. Influence of back belt on the lifting technique throughout a lift was understood using the concept of interjoint coordination. Out of the nine body joint angles, five showed decreased flexion, three increased flexion and the remaining one showed no change in the flexion values. Kinematic relationship was found to exist between hip, knee, trunk and lumbar-thoracic joint. The behavior of postural index values supported the kinematic relationship hypothesis. The back belt affected the proximal to distal interjoint coordination between hip, knee, trunk and lumbar-thoracic joint, thus disturbing the natural style of lifting.
Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern w... more Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern working population. Epidemiological literature suggests that forceful arm exertions pose an increased risk for shoulder MSD development. The majority of shoulder MSDs involve the glenohumeral joint. The glenohumeral joint is characteristically unstable and stabilized by concavity compression mechanism. In this study a biomechanical model of the shoulder complex was used to examine the concavity compression mechanism. Mechanical loading of the glenohumeral joint during forceful arm exertions was analyzed to quantify the angular position of the resultant muscle force vector in 3D space. The resultant muscle force vectors were almost always directed anteriorly, medially, and inferiorly, independent of the magnitude and the direction of the external force application. The knowledge gained in this study could potentially be used to develop a new assessment method to evaluate the risk of injury...
Research has been done on the maximum reach and ingress/egress of upright seats. However, researc... more Research has been done on the maximum reach and ingress/egress of upright seats. However, research on recumbent seats and comparisons between recumbent and upright seats is limited. By using an eight-camera Vicon motion capture system and C-motion Visual 3D modeling software, this research compared the ingress/egress joint kinematics and maximal planar reach of an upright seat with a recumbent seat. Mean range of motion and mean peak angle for each ingress/egress task were determined and the values for the upright seat were compared to the values for the recumbent seat. For each reach task, three extreme points were extracted and compared between the upright and recumbent seat. Seat orientation was found to have a statistically significant effect on the range of motion of several joints during the ingress/egress tasks, as well as one of the extreme points during the reaching tasks.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2014
ABSTRACT Sudden loading during manual material handling poses a significant risk of back injury. ... more ABSTRACT Sudden loading during manual material handling poses a significant risk of back injury. The present study investigated the effect of load holding height on trunk biomechanics (trunk flexion angle and L5/S1 joint compression force) during sudden loading. Eleven subjects were recruited to perform sudden loading tasks with a 6.8 kg load, while maintaining upright standing posture and holding load at three different height levels in the sagittal plane. It has been found that load holding height significantly affected L5/S1 joint compression force and trunk flexion angle. With a lower load holding height, peak L5/S1 joint compression force decreased by 17.5%. According to these findings, it is suggested that holding load at a lower level could help reduce the risk of low back injury.
International Journal of Occupational Safety and Ergonomics Jose, Feb 1, 2009
In this study a multiaxial isokinetic dynamometer was used to measure strength during various upp... more In this study a multiaxial isokinetic dynamometer was used to measure strength during various upper-body isokinetic exertions. Ten male participants performed 7 different upper-body isokinetic exertions. In addition, to evaluate the effect of speed on strength, each participant performed sitting pull exertions at the speed of 0.026, 0.130, and 0.260 m/s. Average isokinetic strength increased from 236.6 +/- 39.1 to 291.8 +/- 65.8 N with the initial increase in speed from 0.026 to 0.130 m/s. The average isokinetic strength decreased to 276.7 +/- 87.2 N with a further increase in speed to 0.260 m/s. The curve between isokinetic strength and speed followed a bell-shaped curve (fitted with the Gaussian function, R(2) = .9). The results of this study could be useful in deciding on the work pace of various manual material handling tasks requiring maximal and/or near maximal exertions.
Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern w... more Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern working population. Epidemiological literature suggests that forceful arm exertions pose an increased risk for shoulder MSD development. The majority of shoulder MSDs involve the glenohumeral joint. The glenohumeral joint is characteristically unstable and stabilized by concavity compression mechanism. In this study a biomechanical model of the shoulder complex was used to examine the concavity compression mechanism. Mechanical loading of the glenohumeral joint during forceful arm exertions was analyzed to quantify the angular position of the resultant muscle force vector in 3D space. The resultant muscle force vectors were almost always directed anteriorly, medially, and inferiorly, independent of the magnitude and the direction of the external force application. The knowledge gained in this study could potentially be used to develop a new assessment method to evaluate the risk of injury...
In this study, the effect of prolonged forward flexion on the recovery process of the reflexive m... more In this study, the effect of prolonged forward flexion on the recovery process of the reflexive muscle activity of the lumbar musculature to its original state is studied using human participants. The behavior of the lower back erector spinae muscle during 20 minutes of forward bending and three hours of recovery was evaluated experimentally using electromyography (EMG) and mathematical modeling. Ten healthy males participated in this study. The EMG of erector-spinae muscle from two different lumbar levels was recorded and expressed as normalized integrated EMG (NIEMG). In general, the average NIEMG values of the erector spinae muscles demonstrated an exponential decrease during the 20-minute loading period. The biexoponential structure, derived from the animal model, did not completely explain the muscle behavior during recovery period. Inclusion of the "intrinsic loading factor" to the biexoponential structure improved the fit of the recovery model to 100%. Most of the r...
International Journal of Occupational Safety and Ergonomics, 2009
In this study a multiaxial isokinetic dynamometer was used to measure strength during various upp... more In this study a multiaxial isokinetic dynamometer was used to measure strength during various upper-body isokinetic exertions. Ten male participants performed 7 different upper-body isokinetic exertions. In addition, to evaluate the effect of speed on strength, each participant performed sitting pull exertions at the speed of 0.026, 0.130, and 0.260 m/s. Average isokinetic strength increased from 236.6 +/- 39.1 to 291.8 +/- 65.8 N with the initial increase in speed from 0.026 to 0.130 m/s. The average isokinetic strength decreased to 276.7 +/- 87.2 N with a further increase in speed to 0.260 m/s. The curve between isokinetic strength and speed followed a bell-shaped curve (fitted with the Gaussian function, R(2) = .9). The results of this study could be useful in deciding on the work pace of various manual material handling tasks requiring maximal and/or near maximal exertions.
Assessment of neuromuscular fatigue is essential for early detection and prevention of risks asso... more Assessment of neuromuscular fatigue is essential for early detection and prevention of risks associated with work-related musculoskeletal disorders. In recent years, discrete wavelet transform (DWT) of surface electromyography (SEMG) has been used to evaluate muscle fatigue, especially during dynamic contractions when the SEMG signal is non-stationary. However, its application to the assessment of work-related neck and shoulder muscle fatigue is not well established. Therefore, the purpose of this study was to establish DWT analysis as a suitable method to conduct quantitative assessment of neck and shoulder muscle fatigue under dynamic repetitive conditions. Ten human participants performed 40min of fatiguing repetitive arm and neck exertions while SEMG data from the upper trapezius and sternocleidomastoid muscles were recorded. The ten of the most commonly used wavelet functions were used to conduct the DWT analysis. Spectral changes estimated using power of wavelet coefficients in the 12-23Hz frequency band showed the highest sensitivity to fatigue induced by the dynamic repetitive exertions. Although most of the wavelet functions tested in this study reasonably demonstrated the expected power trend with fatigue development and recovery, the overall performance of the "Rbio3.1" wavelet in terms of power estimation and statistical significance was better than the remaining nine wavelets.
Sudden unexpected loading has been identified as a risk factor of work-related low back pain (LBP... more Sudden unexpected loading has been identified as a risk factor of work-related low back pain (LBP). This study investigated the effects of different foot placements and load-releasing locations on trunk biomechanics under an unexpected sudden loading event. Fifteen subjects experienced sudden release of a 6.8-kg external load from symmetric or asymmetric directions while maintaining four different foot placements. The results showed that subjects experienced on average 4.1° less trunk flexion, 6.6 Nm less L5/S1 joint moment and 32.0 N less shear force with staggered stance with the right foot forward (the most preferred placement) compared with wide stance (the least preferred placement). Asymmetric load-releasing positions consistently resulted in smaller impacts on trunk biomechanics than symmetric positions. The findings suggest that staggered stance and asymmetric load-holding position can be used as a protective load-handling posture against LBP caused by sudden loading. In a work environment, unexpected sudden loading may cause low back pain (LBP). In this study, we used empirical data to demonstrate how different foot placements and load-releasing locations can be used to mitigate the impact of sudden loading on the spine and to reduce the risk of LBP.
The primary objective of this study was to quantify the effect of dynamic cart pushing exertions ... more The primary objective of this study was to quantify the effect of dynamic cart pushing exertions on the biomechanical loading of shoulder and low back. Ten participants performed cart pushing tasks on flat (0°), 5°, and 10° ramped walkways at 20 kg, 30 kg, and 40 kg weight conditions. An optoelectronic motion capturing system configured with two force plates was used for the kinematic and ground reaction force data collection. The experimental data was modeled using AnyBody modeling system to compute three-dimensional peak reaction forces at the shoulder complex (sternoclavicular, acromioclavicular, and glenohumeral) and low back (lumbosacral) joints. The main effect of walkway gradient and cart weight, and gradient by weight interaction on the biomechanical loading of shoulder complex and low back joints was statistically significant (all p < 0.001). At the lumbosacral joint, negligible loading in the mediolateral direction was observed compared to the anterioposterior and compression directions. Among the shoulder complex joints, the peak reaction forces at the acromioclavicular and glenohumeral joints were comparable and much higher than the sternoclavicular joint. Increased shear loading of the lumbosacral joint, distraction loading of glenohumeral joint and inferosuperior loading of the acromioclavicular joint may contribute to the risk of work-related low back and shoulder musculoskeletal disorder with prolonged and repetitive use of carts.
Http Dx Doi Org 10 1080 00140139 2013 803161, Jun 3, 2013
Lifting tasks performed on uneven ground surfaces are common in outdoor industries. Previous stud... more Lifting tasks performed on uneven ground surfaces are common in outdoor industries. Previous studies have demonstrated that lifting tasks performed on laterally slanted ground surfaces influence lumbar muscle activation and trunk kinematics. In this study, the effect of laterally slanted ground surfaces on the lumbar muscle flexion-relaxation responses was investigated. Fourteen participants performed sagittal plane, trunk flexion-extension tasks on three laterally slanted ground surfaces (0° (flat ground), 15° and 30°), while lumbar muscle activities and trunk kinematics were recorded. Results showed that flexion-relaxation occurred up to 6.2° earlier among ipsilateral lumbar muscles with an increase in laterally slanted ground angle; however, the contralateral side was not affected as much. Our findings suggest that uneven ground alters the lumbar tissue load-sharing mechanism and creates unbalanced lumbar muscle activity, which may increase the risk of low back pain with repeated exposure to lifting on variable surfaces. Uneven ground surfaces are ubiquitous in agriculture, construction, fishing and other outdoor industries. A better understanding of the effects of laterally slanted ground surfaces on the interaction between passive and active lumbar tissues during lifting tasks could provide valuable knowledge in the design of preventive strategies for low back injuries.
Iie Transactions on Occupational Ergonomics and Human Factors, Oct 1, 2013
ABSTRACT Surgical tasks performed using loupes and headlamps were examined to identify exposures ... more ABSTRACT Surgical tasks performed using loupes and headlamps were examined to identify exposures to physical risk factors for work-related musculoskeletal disorders in the neck among microsurgeons. Surgeons who use loupes and headlamps were found to spend extensive time periods working in non-neutral head–neck postures. These postures, and the use of loupes and headlamps, were found to be associated with an increased loading of the cervical spine, which might cumulatively contribute to occupational neck musculoskeletal disorders. To develop effective control strategies, future studies should focus on the impact of design features of loupes (e.g., mount angles, weight, and shape) on head–neck postures during surgical tasks.TECHNICAL ABSTRACT Background: Work-related musculoskeletal disorders in the neck are common among microsurgeons who operate with loupes and headlamps. Published surveys indicate that microsurgeons across many subspecialties believe that loupes contribute to neck musculoskeletal disorders. However, objective data on head–neck posture and cervical loading during surgical tasks performed using loupes and headlamps are currently lacking. Purpose: This study will assess exposures to physical risk factors for neck musculoskeletal disorders during surgical tasks performed using loupes and headlamp. Methods: A field study was performed in operating rooms to measure the head–neck postures commonly used by three ophthalmic plastic surgeons; a subset of microsurgeons. Posture data were used as input to a biomechanical model to estimate cervical spine loading. Results: During nearly 85% of the time spent operating, surgeons adopted asymmetrical head–neck postures characterized by either bending or rotation of >15°, coupled with flexion of >15°. Postures consisting of flexion ≥45°, 15°–30° bending, and 15°–45° rotation produced significantly higher biomechanical loading of the cervical spine compared to near-neutral postures (i.e., flexion, bending and rotation between 0° and 15°). This loading was further exaggerated by the weight of loupes and headlamp. Conclusions: Non-neutral head–neck postures demanded by the dexterous operating tasks performed using loupes and headlamps could be important biomechanical risk factors for cervical musculoskeletal disorders among microsurgeons.
To increase awareness of cervical musculoskeletal disorders (cMSD) in ophthalmic plastic surgeons... more To increase awareness of cervical musculoskeletal disorders (cMSD) in ophthalmic plastic surgeons (OPS) and review strategies for management and prevention. There are objective data that show OPS spend the majority of their time operating in awkward, prolonged, static, asymmetric postures. These postures increase cervical load and cMSD. Loupes and headlamps further increase this cervical loading by 40%. Risk for cMSD is not limited to the operating room. Muscular demands in the anterior deltoid and cervical trapezius are increased in slit lamp biomicroscopy and indirect ophthalmoscopy. Furthermore, the majority of the office visit is spent keyboarding into the electronic medical record which is associated with cMSD. Habitual postural faults result from these cumulative exposures. These must be addressed to prevent further insult and debilitating injury. Successful management requires education in neutral posture, therapeutic exercise, environmental adjustments in the workplace and home, and supported neutral sleep posture. The risks of cMSD in OPS are well established, and nearly 10% of cervical injury will end a career. Neck pain must not be ignored, and experienced professional help is critical. A long-term approach that incorporates exercise, manual therapy, and education is essential for management and prevention.
In this investigation posture restriction caused by back belt is studied. Two-dimensional kinemat... more In this investigation posture restriction caused by back belt is studied. Two-dimensional kinematic data was collected from ten participants using nine marker positions. Angular displacement of nine body angles was compared. Effect of the back belt on the lifting posture was studied using postural index values and kinematic relationship hypothesis. Influence of back belt on the lifting technique throughout a lift was understood using the concept of interjoint coordination. Out of the nine body joint angles, five showed decreased flexion, three increased flexion and the remaining one showed no change in the flexion values. Kinematic relationship was found to exist between hip, knee, trunk and lumbar-thoracic joint. The behavior of postural index values supported the kinematic relationship hypothesis. The back belt affected the proximal to distal interjoint coordination between hip, knee, trunk and lumbar-thoracic joint, thus disturbing the natural style of lifting.
Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern w... more Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern working population. Epidemiological literature suggests that forceful arm exertions pose an increased risk for shoulder MSD development. The majority of shoulder MSDs involve the glenohumeral joint. The glenohumeral joint is characteristically unstable and stabilized by concavity compression mechanism. In this study a biomechanical model of the shoulder complex was used to examine the concavity compression mechanism. Mechanical loading of the glenohumeral joint during forceful arm exertions was analyzed to quantify the angular position of the resultant muscle force vector in 3D space. The resultant muscle force vectors were almost always directed anteriorly, medially, and inferiorly, independent of the magnitude and the direction of the external force application. The knowledge gained in this study could potentially be used to develop a new assessment method to evaluate the risk of injury...
Research has been done on the maximum reach and ingress/egress of upright seats. However, researc... more Research has been done on the maximum reach and ingress/egress of upright seats. However, research on recumbent seats and comparisons between recumbent and upright seats is limited. By using an eight-camera Vicon motion capture system and C-motion Visual 3D modeling software, this research compared the ingress/egress joint kinematics and maximal planar reach of an upright seat with a recumbent seat. Mean range of motion and mean peak angle for each ingress/egress task were determined and the values for the upright seat were compared to the values for the recumbent seat. For each reach task, three extreme points were extracted and compared between the upright and recumbent seat. Seat orientation was found to have a statistically significant effect on the range of motion of several joints during the ingress/egress tasks, as well as one of the extreme points during the reaching tasks.
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2014
ABSTRACT Sudden loading during manual material handling poses a significant risk of back injury. ... more ABSTRACT Sudden loading during manual material handling poses a significant risk of back injury. The present study investigated the effect of load holding height on trunk biomechanics (trunk flexion angle and L5/S1 joint compression force) during sudden loading. Eleven subjects were recruited to perform sudden loading tasks with a 6.8 kg load, while maintaining upright standing posture and holding load at three different height levels in the sagittal plane. It has been found that load holding height significantly affected L5/S1 joint compression force and trunk flexion angle. With a lower load holding height, peak L5/S1 joint compression force decreased by 17.5%. According to these findings, it is suggested that holding load at a lower level could help reduce the risk of low back injury.
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