Biomedical subjects

F A Fathallah

Publications and source records attributed to F A Fathallah.

15 recordsLinked to original sources

PubMed2006

Ergonomic evaluation of winegrape trellis systems pruning operation.

The winegrape industry suffers from high incidence rates of work-related musculoskeletal disorders. Pruning of dormant vines is a significant task, requiring long periods of highly repetitive and physically demanding work. The purpose of this study is to quantitatively evaluate five commonly used winegrape trellis systems with regard to the risk of developing musculoskeletal injuries to the wrist and lower back while pruning. Eleven subjects participated in this study. Subjects performed a simulated pruning task as wrist and trunk postures were gathered using electrogoniometers. The results showed significant postural differences among the trellis systems. Compared to the other systems, the VSP was determined to be the optimal system in terms of decreasing relative MSD risk. These results will assist vineyards in the selection process of suitable trellis systems that will include the worker health aspect in conjunction with other trellis-related parameters such as grape quality and productivity.

Adult↗

PubMed2004

The effect of feedback training on lumbosacral compression during simulated occupational lifting.

This study measured the effect of a feedback training program on lumbar compression during simulated occupational lifting. Two distinct types of feedback were compared: real-time electromyographic feedback, vs. an acceleration index delivered verbally post-lift. Kinematic data were collected from 28 subjects during symmetrical sagittal plane lifts. Following a baseline session, two feedback training sessions were provided, with a 1-week interval between each session. A control group followed the same protocols, but without receiving feedback training. A post-training session, using protocols identical to the baseline session, was used to assess pre-to-post changes in the dependent variable: peak lumbosacral compression computed using a dynamic linked-segment model. All three groups showed reductions in peak compression from pre-to-post: on average the control group improved by 11.2%, the EMG group by 16.7%, and the acceleration group by 25.3%. The results revealed an interaction between the improvement and the group (p=0.023), and a difference between the improvement in the control group and that in the verbal acceleration feedback group (p<0.01). These reductions in lumbosacral compression persisted after a 7-day interval without feedback training, suggesting that this approach could provide sustained risk-reduction during manual materials handling.

Acceleration↗

PubMed2001

Timing of activation of the erector spinae and hamstrings during a trunk flexion and extension task.

STUDY DESIGN: Timing of activation of the hamstrings and erector spinae was assessed using surface electromyography. OBJECTIVES: To investigate the influence of posture and movement speed during trunk flexion-extension on the flexion-relaxation response and trunk muscle activation patterns. SUMMARY OF BACKGROUND DATA: The literature contains numerous reports on coactivity and synergistic behavior of major muscle groups during trunk flexion-extension. There are few reports on the timing of muscle activation. METHODS: Six subjects were recruited for a training session and six biweekly test sessions. Ten surface electromyogram electrodes and a lordosimeter were used to record timing of lumbar motion and muscle recruitment in the hamstrings and at four sites in the thoracolumbar region. A 3 x 2 within-subject factorial design was used to test the effects of posture and speed on activation patterns. RESULTS: Patterns of muscle activation were found to be dependent on posture and the direction of movement. The flexion-relaxation response was pervasive in the lumbar region but was less consistent at the T9 and hamstring sites. Significant differences in the delay between electromyogram activation and lumbar motion were found for the standing postures at initiation of extension, in which activation progressed in the caudad-to-cephalad direction. CONCLUSIONS: The flexion-relaxation response is ubiquitous in the lumbar erector spinae and is present in the hamstrings and lower thoracic erector spinae, although not consistently in all subjects. In standing, timing of activation differed significantly by site in extension but not in flexion. Muscle activation patterns and flexion-relaxation were consistent over six biweekly test sessions.

Adult↗

PubMed2001

Influence of measurement accuracy on the application of the 1991 NIOSH equation.

A relatively neglected topic in manual materials handling (MMH) research is the impact of the accuracy of task parameter measurements on the application of various assessment methods. A laboratory experiment was conducted to investigate the accuracy of NIOSH equation parameter measurements made by eight subjects following a 4-h training session. Five individual tasks were measured; two were single tasks and three were part of a multiple-component simulated palletizing operation. Significant differences between reference parameter measurements and average measurements made by subjects were found. The sensitivity analysis showed that frequency and horizontal location are the most important parameters. These parameters also tended to have the highest measurement errors. Recommendations for increasing the effectiveness of training programs for NIOSH equation users based on the results of the study are presented.

Ergonomics↗

PubMed2000

Maximum forces sustained during various methods of exiting commercial tractors, trailers and trucks.

Many commercial vehicles have steps and grab-rails to assist the driver in safely entering/exiting the vehicle. However, many drivers do not use these aids. The purpose of this study was to compare impact forces experienced during various exit methods from commercial equipment. The study investigated impact forces of ten male subjects while exiting two tractors, a step-van, a box-trailer, and a cube-van. The results showed that exiting from cab-level or trailer-level resulted in impact forces as high as 12 times the subject's body weight; whereas, fully utilizing the steps and grab-rails resulted in impact forces less than two times body weight. An approach that emphasizes optimal design of entry/exit aids coupled with driver training and education is expected to minimize exit-related injuries.

Adult↗

PubMed2000

Prospective validation of a low-back disorder risk model and assessment of ergonomic interventions associated with manual materials handling tasks.

The evaluation of low-back disorder risk associated with materials handling tasks can be performed using a variety of assessment tools. Most of these tools vary greatly in their underlying logic, yet few have been assessed for their predictive ability. It is important to document how well an assessment tool realistically reflects the job's injury risk, since only valid and accurate tools can reliably determine whether a given ergonomic intervention will result in a future reduction in back injuries. The goal of this study was to evaluate how well a previously reported low-back disorder (LBD) risk assessment model (Marras et al. 1993) could predict changes in LBD injury rates as the physical conditions to which employees are exposed were changed. Thirty-six repetitive materials handling jobs from 16 different companies were included in this prospective cohort study. Of these 36 jobs, 32 underwent an ergonomic intervention during the observation period, and four jobs in which no intervention occurred served as a comparison group. The trunk motions and workplace features of 142 employees performing these jobs were observed both before and after workplace interventions were incorporated. In addition, the jobs' LBD rates were documented for these pre- and post-intervention periods. The results indicated that a statistically significant correlation existed between changes in the jobs' estimated LBD risk values and changes in their actual low-back incidence rates over the observation period. Linear and Poisson regression models also were developed to predict a change in a job's incidence rate and the number of LBD on ajob respectively, as a function of the job's risk change using this assessment model. Finally, this prospective study showed which ergonomic interventions consistently reduced the jobs' mean low-back incidence rates. These results support use of the LBD risk model to assess accurately a job's potential to lead to low-back injuries among its employees.

Adult↗

PubMed1999

Regression models for predicting peak and continuous three-dimensional spinal loads during symmetric and asymmetric lifting tasks.

Most biomechanical assessments of spinal loading during industrial work have focused on estimating peak spinal compressive forces under static and sagittally symmetric conditions. The main objective of this study was to explore the potential of feasibly predicting three-dimensional (3D) spinal loading in industry from various combinations of trunk kinematics, kinetics, and subject-load characteristics. The study used spinal loading, predicted by a validated electromyography-assisted model, from 11 male participants who performed a series of symmetric and asymmetric lifts. Three classes of models were developed: (a) models using workplace, subject, and trunk motion parameters as independent variables (kinematic models); (b) models using workplace, subject, and measured moments variables (kinetic models); and (c) models incorporating workplace, subject, trunk motion, and measured moments variables (combined models). The results showed that peak 3D spinal loading during symmetric and asymmetric lifting were predicted equally well using all three types of regression models. Continuous 3D loading was predicted best using the combined models. When the use of such models is infeasible, the kinematic models can provide adequate predictions. Finally, lateral shear forces (peak and continuous) were consistently underestimated using all three types of models. The study demonstrated the feasibility of predicting 3D loads on the spine under specific symmetric and asymmetric lifting tasks without the need for collecting EMG information. However, further validation and development of the models should be conducted to assess and extend their applicability to lifting conditions other than those presented in this study. Actual or potential applications of this research include exposure assessment in epidemiological studies, ergonomic intervention, and laboratory task assessment.

Adult↗

PubMed1998

The role of complex, simultaneous trunk motions in the risk of occupation-related low back disorders.

STUDY DESIGN: Simultaneous trunk kinematic variables of industrial workers performing jobs with varying degrees of low back disorder risk were quantified, by using a three-dimensional electrogoniometer. OBJECTIVES: To assess the distinguishing patterns of simultaneous multidimensional (complex) motion parameters of workers performing manual material handling jobs with varying degrees of low back disorder risk. SUMMARY OF BACKGROUND DATA: There is significant epidemiologic and biomechanical evidence that implicates simultaneously occurring or combined motions and loading as important risk factors follow back disorder. However, the specific levels or magnitudes and patterns of these complex motions at which risk of low back disorder is increased are still unknown. METHODS: An industrial database of 126 workers and jobs was used to quantify the complex trunk motions of groups with varying degrees of low back disorder risk. Three groups, low-, medium-, and high-risk, were defined on the basis of retrospective injury records of the corresponding jobs. The jobs were further classified into five cells of weight-lift rate combinations. Within each weight-lift rate cell, the three-dimensional trunk motion patterns of workers were analyzed. Bivariate distributions and cumulative distribution functions were used to compare the simultaneous occurrence of complex dynamic motions among risk groups. RESULTS: High- and medium-risk groups exhibited complex trunk motion patterns involving high magnitudes of combined velocities, especially at extreme sagittal flexion; whereas the low-risk group did not. Postural trunk information alone did not provide a consistent pattern of distinguishing among risk groups. CONCLUSIONS: Elevated levels of complex simultaneous velocity patterns were unique to groups with increased low back disorder risk. Knowledge of these complex trunk velocity patterns in combination with key workplace factors provides a more sensitive means for identifying low back disorder occupational risk factors than does mere postural information.

Back Injuries↗

PubMed1998

An assessment of complex spinal loads during dynamic lifting tasks.

STUDY DESIGN: An electromyogram-assisted free-dynamic lifting model was used to quantify the patterns of complex spinal loads in subjects performing various lifting tasks. OBJECTIVES: To assess in vivo the three-dimensional complex spinal loading patterns associated with high and low risk lifting conditions that matched those observed in industrial settings. SUMMARY OF BACKGROUND DATA: Combined loading on the spine has been implicated as a major risk factor in occupational low back disorders. However, there is a void in the literature regarding the role of these simultaneously occurring complex spinal loads during manual lifting. METHODS: Eleven male subjects performed symmetric and asymmetric lifting tasks with varying speed and weight. Reactive forces and moments at L5-S1 were determined through the use of electrogoniometers and a force plate. An electromyogram-assisted model provided the continuous patterns of three-dimensional spinal loads under these complex lifting tasks. RESULTS: The results showed that complex dynamic motions similar to those observed in risky industrial tasks generated substantial levels of combined compressive and shear loads. In addition, higher loading rates were observed under these conditions. Unlike loading magnitudes, loading rate was a better indicator of dynamic loading because it incorporated both the duration and magnitude of net muscle forces contributing to total spinal loading during the lifting conditions. CONCLUSIONS: Quantification of spinal combined motions and loading in vivo has not been undertaken. This study provided a unified assessment of the effects of combined or coupled motions and moments in the internal loading of the spine. Dynamic lifting conditions similar to those observed in risky industrial situations generated unique complex patterns of spinal loading, which have been implicated to pose a higher risk to the spinal structure. The higher predicted loading and loading rate during asymmetric lifting conditions can be avoided by appropriate ergonomic workplace modifications.

Adult↗

PubMed1997

Challenges in assessing risk factors in epidemiologic studies on back disorders.

In epidemiologic studies on musculoskeletal disorders, some risk factors, especially physical load, cannot be determined independently from the worker. Posture, movement and external load are the result both of physical work requirements forced on the worker and of the worker's capacity to adopt particular techniques. Risk factors are also adjusted in relation to the worker's health. This paper presents a dynamic model that links exposure to risk factors for back pain and disability. Its aim is to help identify core elements in exposure assessment strategies for epidemiologic studies on back disorders. In this dynamic model, risk factors are determined relative to health status in order to distinguish between etiological and prognostic factors. Measurement techniques for various risk factors are classified into self-reports, observations, and direct instrumentation. Features of commonly used techniques are discussed with respect to feasibility, accuracy, and precision. In addition, consideration is given to the optimum allocation of measurements taking into account the effects of random and systematic variation in exposure due to tasks, workplaces, and workers.

Back Pain↗

PubMed1997

A method for measuring external spinal loads during unconstrained free-dynamic lifting.

Biomechanical lifting models often require the knowledge of the applied trunk moments and forces for model validation purposes and/or to determine loading levels experienced at various joints of the body. Trunk kinetic data under dynamic exertions are commonly difficult to attain without restrictive anatomic/anthropometric assumptions and cost or constraining body motion. The main objectives of the study were to present a new technique for determining continuous three-dimensional forces and moments about the L5/S1 spinal joint, and to validate the technique and assess its applicability under lifting situations. A combination of a force plate and two electrogoniometers facilitated the determination of trunk kinetics about L5/S1. An apparatus was devised to allow the application of various actual moments that were compared to their corresponding predicted moments. The results showed that, over all the conditions considered, the average percent error in estimating the actual applied moment(s) was about 4% (2.3 S.D.), with a test-retest reliability approaching unity. Given such agreement, along with the relative ease and directness of the method, it is believed that this approach should be applicable under most lifting conditions. The technique offers a fairly accurate measure of trunk moments without the need for constraining the motion of any body joint.

Biomechanical Phenomena↗

PubMed1996

A method for measuring external loads during dynamic lifting exertions.

Biomechanical analyses of lifting exertions often require measured values of applied trunk moments and forces as baseline or validation data. Accurate measures of the trunk kinetic data are difficult to achieve from dynamic exertions without significant approximation, cost, or motion constraints. The purpose of this effort was to develop and validate a means to directly measure multi-dimensional, trunk moments which occur during dynamic lifting exertions. Force plate reaction loads coupled through a lower-body isolation structure designed to fasten the hips and legs into a known static position, were employed to compute the moment vectors about the lumbar spine. Results demonstrate the applied moments about the lumbo-sacral junction of the spine can be accurately measured from a single force plate, allowing biomechanical evaluation of dynamic lifting exertions without constraining the motions of the upper body.

Adult↗

PubMed1995

Biomechanical risk factors for occupationally related low back disorders.

A continuing challenge for ergonomists has been to determine quantitatively the types of trunk motion and how much trunk motion contributes to the risk of occupationally-related low back disorder (LBD). It has been difficult to include this motion information in workplace assessments since the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of LBD during occupational lifting in industry. Over 400 industrial lifting jobs were studied in 48 varied industries. The medical records in these industries were examined so that specific jobs historically categorized as either low, medium, or high risk for occupationally-related LBD could be identified. A tri-axial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers worked at these low, medium, or high risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model indicated that a combination of five trunk motion and workplace factors predicted well both medium risk and high risk occupational-related LBD. These factors included lifting frequency, load moment, trunk lateral velocity, trunk twisting velocity, and trunk sagittal angle. Increases in the magnitude of these factors significantly increased the risk of LBD. The analyses have enabled us to determine the LBD risk associated with combined changes in the magnitudes of the five factors. The results indicate that by suitably varying these five factors observed during the lift collectively, the odds of high risk group membership may decrease by over ten times. These results were related to the biomechanical, ergonomic, and epidemiologic literature. The five trunk motion and workplace factors could be used as quantitative, objective measures to redesign the workplace so that the risk of occupationally-related LBD is minimized.

Biomechanical Phenomena↗

PubMed1995

Diurnal variation in trunk kinematics during a typical work shift.

Diurnal variation in trunk flexibility, defined as changes in range of motion, has been previously observed and quantified. Prior studies have shown that decreased disk height occurs as the day progresses and allows the spinal ligaments to slacken, resulting in an increase in the range of motion (flexibility) and a possible reduction in the risk of injury. This risk may be accentuated under dynamic motions of the spine. This study was conducted to observe the change in dynamic trunk mobility as a function of time of the day. Trunk motions of 21 men were observed at three specific times of the day using a triaxial electrogoniometer. No variation in trunk range of motion in any of the cardinal planes was observed. However, velocity and acceleration in the sagittal plane showed significant variations, suggesting the reexamination of the "slack ligaments" hypothesis. This study asserts that identifying flexibility by only its static component, range of motion, gives only partial information about the diurnal variation experienced by the spine. Industrial injuries occurring in the early morning hours may be a result of insufficient trunk mobility. This study indicates that risk associated with diurnal variation is far more complex than originally thought.

Acceleration↗

PubMed1993

The role of dynamic three-dimensional trunk motion in occupationally-related low back disorders. The effects of workplace factors, trunk position, and trunk motion characteristics on risk of injury.

Current ergonomic techniques for controlling the risk of occupationally-related low back disorder consist of static assessments of spinal loading during lifting activities. This may be problematic because several biomechanical models and epidemiologic studies suggest that the dynamic characteristics of a lift increase spine loading and the risk of occupational low back disorder. It has been difficult to include this motion information in workplace assessments because the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of low back disorder during occupational lifting in industry. More than 400 repetitive industrial lifting jobs were studied in 48 varied industries. Existing medical and injury records in these industries were examined so that specific jobs historically categorized as either high-risk or low-risk for reported occupationally-related low back disorder could be identified. A triaxial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers lifted in these high-risk or low-risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model was developed, based on biomechanical plausibility, and indicated that a combination of five trunk motion and workplace factors distinguished between high and low risk of occupationally-related low back disorder risk well (odds ratio: 10.7). These factors included 1) lifting frequency, 2) load moment, 3) trunk lateral velocity, 4) trunk twisting velocity, and 5) the trunk sagittal angle. This analysis implies that by suitably varying these five factors observed during the lift collectively, the odds of high-risk group membership may decrease by almost 11 times. The predictive power of this model was found to be more than three times greater than that of current lifting guidelines. This study, though not proving causality, indicates an association between the biomechanical factors and low back disorder risk. This model could be used as a quantitative, objective measure to design the workplace so that the risk of occupationally-related low back disorder is minimized.

Biomechanical Phenomena↗