PRIMARY OBJECTIVE: The primary objective of this study was to determine the extent and severity o... more PRIMARY OBJECTIVE: The primary objective of this study was to determine the extent and severity of the musculoskeletal problems in office workers in a telecommunication company.RESEARCH DESIGN: A questionnaire survey was conducted to assess the prevalence of musculoskeletal disorders' symptoms, their perceived intensity and interaction with ability to work among office workers.METHODS AND PROCEDURES: The Cornell Musculoskeletal Discomfort Questionnaire and Cornell Hand Discomfort Questionnaire developed by the Human Factors and Ergonomics Laboratory at Cornell University were used on a sample of 140 office workers in a telecommunication company.MAIN OUTCOMES AND RESULTS: Discomfort/pain/ache at the wrist level was reported by 86.5% for the left side and 95.5% for the right side. Additionally, discomfort/pain/ache was reported by 77.5% of the sample for neck and 31% of the sample for the left and 50% for the right shoulder region. At the hand site, the area in the distal proximity of the wrist was the most affected site being indicated in 90% of cases for left side and 95% of cases for the right side.CONCLUSIONS: An overview of problems associated with the body parts in office work may allow targeted prevention and intervention.
To determine the functional capability in asymmetric trunk motion, isometric and isokinetic later... more To determine the functional capability in asymmetric trunk motion, isometric and isokinetic lateral flexion and axial rotation strengths of a normal and patient samples were measured. Seventy-three normal asymptomatic subjects (41 males and 32 females) and ten patients (9 males and 1 female) were tested. The dual objectives of the study were to develop a database for isometric and isokinetic lateral flexion and axial rotation strength capabilities of a normal sample and to determine the functional impairment of a sample of patients. More than 60% of low back injuries are associated with trunk twisting. Asymmetric motions are important risk factors. However, strength capability data for axial rotation are sparse and those for lateral flexion nonexistent. To achieve the objectives of the study, two devices were designed and fabricated. Isometric lateral flexion was tested bilaterally in neutral posture and at 10 degrees, 20 degrees, and 30 degrees of lateral bending. Isometric axial rotation was tested bilaterally in neutral posture and at 5 degrees, 10 degrees, 15 degrees, and 20 degrees of axial rotation. Isokinetic lateral flexion and axial rotation strengths were tested bilaterally starting from the neutral posture. The strength invariably declined progressively for all groups with increasing postural asymmetry. The strength in isokinetic activities ranged between 60% to 70% of the strength measured in isometric activities. All groups were significantly stronger in lateral flexion compared with axial rotation. The female sample ranged between 60% to 70% values of males for all activities studied. The patient group was weakest, ranging between 45% to 55% for isometric and 52% to 58% for isokinetic activities of their control group.
Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have s... more Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have suggested that dental professionals may suffer from musculoskeletal disorders (MSDs) of the low back and neck as well as other MSDs. This survey aimed to look deeper into MSDs among orthodontists and provide a starting point to direct ergonomic intervention. The standardized Nordic questionnaire was
To determine the functional capability in asymmetric trunk motion, isometric and isokinetic later... more To determine the functional capability in asymmetric trunk motion, isometric and isokinetic lateral flexion and axial rotation strengths of a normal and patient samples were measured. Seventy-three normal asymptomatic subjects (41 males and 32 females) and ten patients (9 males and 1 female) were tested. The dual objectives of the study were to develop a database for isometric and isokinetic lateral flexion and axial rotation strength capabilities of a normal sample and to determine the functional impairment of a sample of patients. More than 60% of low back injuries are associated with trunk twisting. Asymmetric motions are important risk factors. However, strength capability data for axial rotation are sparse and those for lateral flexion nonexistent. To achieve the objectives of the study, two devices were designed and fabricated. Isometric lateral flexion was tested bilaterally in neutral posture and at 10 degrees, 20 degrees, and 30 degrees of lateral bending. Isometric axial rotation was tested bilaterally in neutral posture and at 5 degrees, 10 degrees, 15 degrees, and 20 degrees of axial rotation. Isokinetic lateral flexion and axial rotation strengths were tested bilaterally starting from the neutral posture. The strength invariably declined progressively for all groups with increasing postural asymmetry. The strength in isokinetic activities ranged between 60% to 70% of the strength measured in isometric activities. All groups were significantly stronger in lateral flexion compared with axial rotation. The female sample ranged between 60% to 70% values of males for all activities studied. The patient group was weakest, ranging between 45% to 55% for isometric and 52% to 58% for isokinetic activities of their control group.
Isometric and isokinetic trunk flexion-extension strengths were studied among 73 subjects (41 mal... more Isometric and isokinetic trunk flexion-extension strengths were studied among 73 subjects (41 males and 32 females) and 10 patients (9 males and 1 female). The isometric strengths were measured in four postures of trunk flexion. The isokinetic trunk strengths were measured through the range of these postures. The study had two objectives: to develop a database for isometric flexion-extension strength at different levels of trunk flexion and isokinetic strength at corresponding angles and to determine the decrement in strength characteristics among patients of idiopathic low back pain. Though flexion-extension strength among normal subjects and patients has been studied, its variation due to standardized postural change has not been reported extensively. The influence of postural deviation on flexion-extension ratios are also largely unknown. To achieve the objectives of the study, a device flexion-extension-lateral flexion tester (FELT) was designed and fabricated. The male and female subjects performed isometric flexion and extension at 0 degree, 20 degrees, 40 degrees and 60 degrees of trunk flexion; and isokinetic flexion starting at neutral posture, and isokinetic extension starting at 60 degrees of trunk flexion. The patients performed isometric flexion and extension in neutral posture only; and isokinetic flexion-extension similar to normal sample. The average strength in each activity was between 70 and 80% of the corresponding peak strength. The isokinetic activity strengths ranged between 60 and 70% of the corresponding isometric activities in each group. The strength of females ranged between 60 and 70% of males. The ANOVA revealed that posture had a significant effect on strength. The multiple regression explained 73% of variance in isometric and 34% in isokinetic modes. A patient's strength profile should be determined in a posture that simulates activities of daily living to determine impairment and plan rehabilitation.
It is generally acknowledged that compensation payments (WCB) influence rehabilitation outcome in... more It is generally acknowledged that compensation payments (WCB) influence rehabilitation outcome in a negative manner. Patients receiving WCB have more treatment over a longer time period than their non compensated (NWCB) cohorts. It is not clear whether therapists (PT) perceive WCB clients as being more impaired and expect them to have a worse outcome than clients without WCB. The purpose of this study was to determine whether PTs' clinical judgments are influenced by the knowledge of a patients WCB status and whether this knowledge influences their assessment findings or prognostic judgments. A convenience sample of 69 physical therapists (PTs) participated. Each PT viewed three videotaped assessments, of patients with low back pain (LBP) that differed in severity. The PT was provided with a brief history of the patient. Included in the history was a statement that the patient was (WCB group), or was not (NWCB group) in receipt of workers compensation benefits (WCB). The third group of PTs was given no information (control group) about the patient. PTs recorded physical assessment findings and made prognostic judgments about the patients. Data for the physical assessment findings and prognoses recorded by the PTs was analyzed across information groups using ANOVA. Knowledge of compensation status did not influence the PTs' physical assessment findings but did influence prognostic judgments. WCB status was deemed to have a negative effect on outcome in patients with mild LBP. Additionally, NWCB status was deemed to have a positive influence on outcome in patients with severe LBP. The differences were most marked in the short term (1 month). It was concluded that PTs expectations of outcome are influenced by prior knowledge of compensation status.
International Journal of Industrial Ergonomics, 2003
So far, many different studies have examined possible implications of typing related posture and ... more So far, many different studies have examined possible implications of typing related posture and activity on carpal tunnel syndrome (CTS) incidence. Although they tend to present the findings as very apparent ones, assessing the complex relationships between the different causal factors implicated in keyboarding and in the usage of pointing devices, on the one hand, and work related upper extremity disorders (WRUED), especially CTS, on the other hand, is problematic. The aim of this review paper is to outline relevant information about CTS risk factors present in data entry task and their implications, with a special emphasis on different extreme postures determined by conventional and alternate keyboards, pointing devices and their role in the development of CTS. Secondly, a comparison of several keyboards with respect to design of keyswitch to reduce force and its effect on carpal tunnel pressure (CTP) is provided. This review critically considers the factors implicated in the occurrence of CTS due to computer work, analysing the determining factors from a well-considered perspective instead of considering them separate entities. Many ''ergonomic'' keyboards change the musculoskeletal region exposed to risk, instead of eliminating hazardous postures. The ergonomic assessment of new devices should precede their introduction and not follow it. Future research should be directed to establish a comprehensive understanding of what combinations of trigger factors should be eliminated or modified, to assess the impact of workstation redesign and to uncover the interrelationships between different factors that contribute to the development of CTS.
International Journal of Industrial Ergonomics, 2002
Theoretical assumptions become valid only when they are tested empirically. Whenever measurement ... more Theoretical assumptions become valid only when they are tested empirically. Whenever measurement instruments are used one needs to be sure that they yield accurate information for the construct of interest. This article outlines the measurement instruments properties and their impact on research as well as the differences and similarities between biases that could occur in different measurement and data collection procedures. Important criteria that must be met when developing a new measuring tool are presented in detail. The purpose of this review paper is to gather and organize the relevant information regarding measurement bias in research. It outlines important steps that will lead to a decreased error in measurement and data collection. As more and more ergonomic decisions are taken, based on the research outcome, the impact of the quality of measurement in various intervention programs becomes increasingly critical.
International Journal of Industrial Ergonomics, 2004
Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have s... more Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have suggested that dental professionals may suffer from musculoskeletal disorders (MSDs) of the low back and neck as well as other MSDs. This survey aimed to look deeper into MSDs among orthodontists and provide a starting point to direct ergonomic intervention. The standardized Nordic questionnaire was
International Journal of Industrial Ergonomics, 1994
Ten normal young adult females (mean age 26.8 years, mean weight 50.9 kg, mean height 165.9 cm) p... more Ten normal young adult females (mean age 26.8 years, mean weight 50.9 kg, mean height 165.9 cm) performed maximal and subjectively graded exertions of the stoop lift, hand grip, and finger pinch. The levels of graded exertion required were 80%, 60%, 40% and 20% of maximal voluntary contraction (MVC). The sequences of all conditions were fully randomized. Each of the randomized conditions was tried three times in succession. The entire experiment was carried out on four different days at the same time of the day on Monday, Wednesday, Friday of one week and Friday of the next week. The data obtained were subjected to descriptive and statistical analysis with t-test, analysis of variance, and correlation and regression. There were significant differences in the effort produced in three different activities (p < 0.01). The levels of exertion from 20% to 80% were all significantly different from each other (p < 0.01). However, there were no significant differences between the three trials of any given condition and the exertions produced on four different days. The 80% and 60% of exertions were overestimated and 20% was underestimated compared to the objective values based on MVC (p < 0.01). At 40% effort there was no significant difference between the objective level of exertion and subjectively gauged and produced effort for all three activities. The reliability of perception among the female subjects was similar for finger pinch, hand grip, and stoop lift activities.
International Journal of Industrial Ergonomics, 1991
Industrial activities are mediated through strength application. Physically demanding tasks are k... more Industrial activities are mediated through strength application. Physically demanding tasks are known to precipitate overexertion injuries. Therefore, this study was conducted to investigate the effect of posture on torque producing capability of the back. Fourteen volunteers (5 male students with mean age 25.4 yrs, mean height 178.3 cm and mean body weight 73.9 kg; 9 female students with mean age 20.8 yrs, mean height 165.9 cm and mean body weight of 56.1 kg) exerted their maximal isometric torque in lying, seated and upright postures. The lower body (hip down) was stabilized at the same places -hip, above and below knee, and at the ankle in all three postures. The subjects exerted their maximal voluntary effort for 5 seconds in attempted flexion, extension, and left and right lateral flexion. The sequence of test conditions was randomized. The torque produced in lying posture was significantly lower than those in standing or sitting postures (p < 0.01). They represented 35% to 61% of the standing posture in males and 46% to 53% among females. In all postures among both sexes extension torque was highest except men's standing flexion. The torque producing capability in lying posture was significantly less ( p < 0.01). The trunk torques of females ranged between 42% to 69% of males. Due to a large effect of posture on strength, a standardization of test postures is suggested for screening of industrial workers.
Postural and therefore biomechanical standardization in strength testing has not been rigorously ... more Postural and therefore biomechanical standardization in strength testing has not been rigorously and consistently applied. To develop a quantitative relationship between strength and posture (body position, symmetry, and reach) 30 normal subjects (18 male and 12 females) were required to stoop and squat lift or exert in the relevant posture against a standardized instrumented handle. The isometric lifting efforts and isokinetic lifts were studied. The isokinetic lifts were done at a linear velocity of 50cm/s of the hand displacement from the floor to the knuckle heights of the respective subjects in stoop and squat postures. The isometric stoop lifting efforts were exerted in two standardized postures: (a) with 60 degrees hip flexion; and (b) with 90 degrees hip flexion. The isometric squat lifting efforts were also exerted in two standardized postures: (a) with 90 degrees knee flexion; and (b) with 135 degrees knee flexion. All isometric lifting efforts and isokinetic lifts were performed at half, three-quarters, and full horizontal reach in sagitally symmetrical, 30 degrees left lateral, and 60 degrees left lateral planes. Isometric stoop and squat lifting efforts were also measured in self-selected optimal postures. These 56 conditions were tested in random order. The analysis of variance revealed that the gender, the mode of lifting, the postural asymmetry and reach of lifting affected the strength significantly (p less than 0.0001). Most two-way and three-way interactions were significant (p less than 0.01). Of 108 prediction regression equations, 103 were significant with up to 90% of the variation explained by anthropometric variables and sagittal plane strength. The reach affected the strength most profoundly followed by postural asymmetry and the mode of lifting.
Musculoskeletal disorders of back and neck among orthodontists are prevalent. Due to low instanta... more Musculoskeletal disorders of back and neck among orthodontists are prevalent. Due to low instantaneous load they have not been investigated. The present study aimed to quantify and compare instantaneous and cumulative loads on low back and neck in orthodontists. The sample included nine graduate orthodontic students from the University of Alberta and one practicing orthodontist to validate the generalization from student to professional group. The subjects were videotaped performing regular duties and the recorded postures were printed for biomechanical analysis of compression and shear loads and exposure time. Instantaneous loads were calculated using a biomechanical model developed specifically for this study and cumulative loads were calculated from the resultant loads. The average instantaneous low back compression loads for men and women were found to be 1383 N and 936 N respectively. The average daily cumulative load on the other hand were found to be 16.2 MNs and 9.9 MNs for males and females respectively. The study demonstrates that smaller loads cannot be ignored due to their magnitude if their duration is long because the time dependent properties of the tissues become modulating factor. Thus the measurement of instantaneous loads on tasks in orthodontists is not indicative of the amount of cumulative stress experienced by them.
Journal of Occupational Rehabilitation, Dec 1, 2001
This paper reviews the current state of knowledge regarding the tools used in evaluating the work... more This paper reviews the current state of knowledge regarding the tools used in evaluating the workplace and worker in hopes of preventing low-back injury. Information regarding the current state of expenditure and trends toward ergonomic intervention are discussed. Acknowledgment is made of the increasing shift of responsibility from Compensation Boards to industry, and a review proactive preventative strategies and medical knowledge is included. Current ergonomic assessment tools are reviewed and the role of the Physical Ergonomist is introduced. Suggestions are made regarding the value of current and future approaches in prevention and direction of research.
... Human muscle strength definitions, measurement, and usage" Part II -The scientific basis... more ... Human muscle strength definitions, measurement, and usage" Part II -The scientific basis (knowledge base) for the guide Anil MitaP'*, Shrawan Kumar ba Ergonomics and Engineering Controls Research Laboratory, College of Engineering, University of Cincinnati, Cincinnati ...
Http Dx Doi Org 10 1080 00140130500435595, Feb 20, 2007
The objective of this study was to determine the best variable, if any, to indicate the level of ... more The objective of this study was to determine the best variable, if any, to indicate the level of localized muscle fatigue. Six male and six female subjects were studied while they exerted their maximal voluntary contraction and 40% of maximal voluntary contraction of spinal extensors in an isometric lifting activity. The electromyography (EMG) of erectores spinae at thoracic and lumbar levels was measured bilaterally. Also, the muscle bed blood volume, level of blood oxygenation to erector spinae at L3 level and heart rate were measured. The initial and final values of subjective feelings of fatigue through visual analogue score, rate of perceived exertions and body part discomfort rating were recorded. The mean maximal voluntary contraction forces for males and females were 899 (238) N and 431 (135) N respectively. The mean durations of hold in maximal voluntary fatiguing contraction were 68.1 (39.9) s and 72.3 (37.0) s for men and women respectively. By the end of the hold the force declined to 52% for males and 62% for females. The EMG amplitudes and median frequencies also progressively declined (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). ANOVA revealed that the task percentile values of all variables were significantly different (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Gender had a significant main effect (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). The correlation coefficients between force and other individual variables were weak to modest, but significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). None of the single variables predicted fatigue reliably for either gender and levels of contraction. The regression equations developed were highly significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) and they explained 96 to 98% of variance in both genders and contractions.
Http Dx Doi Org 10 1080 00140139208967362, May 31, 2007
Despite numerous efforts to control occurrences of work-related low back pain, it continues to be... more Despite numerous efforts to control occurrences of work-related low back pain, it continues to be a significant problem. Since the causation of low back pain is under multifactorial control, it is suggested that the factor most vulnerable at any given time will determine the safety. Epidemiological, biomechanical, physiological, and psychophysical information presented in published literature has been analysed. The data available are related to injuries and the projected margin of safety. This paper therefore, is an integrative, inferential synthesis of the published work to discern the margin of safety. An attempt has been made to conclude, on the basis of objective evidence, an all encompassing criterion to ensure the safety of the back. The psychophysical approach appears to integrate biomechanical and physiological variables on a short term basis in the studies surveyed. However, it remains to be proven that the sensory conditioning due to prolonged and repetitive occupational tasks will remain responsive to cumulative load and fatigue failures.
International Journal of Occupational Safety and Ergonomics Jose, Feb 1, 2008
Two types of computer input devices, a conventional mouse and a roller bar one, were studied in t... more Two types of computer input devices, a conventional mouse and a roller bar one, were studied in terms of muscular activity in m. trapezius dexter, m. deltoideus anterior dexter and m. extensor digitorum dexter, and comfort rating. Fifteen university students and employees participated in this study. The order of the devices was random. While a task was performed, electromyography (EMG) data were recorded for each test. Muscular activity was found to be significantly lower for the roller bar mouse than for the conventional one. Comfort rating indicated there was a significant difference in moving a cursor with the conventional mouse compared to the roller bar one. It is concluded that a roller bar mouse allowed the subjects to work closer to the body compared to the conventional one, thus the former can be recommended as a general means of reducing upper extremity musculoskeletal disorders.
PRIMARY OBJECTIVE: The primary objective of this study was to determine the extent and severity o... more PRIMARY OBJECTIVE: The primary objective of this study was to determine the extent and severity of the musculoskeletal problems in office workers in a telecommunication company.RESEARCH DESIGN: A questionnaire survey was conducted to assess the prevalence of musculoskeletal disorders' symptoms, their perceived intensity and interaction with ability to work among office workers.METHODS AND PROCEDURES: The Cornell Musculoskeletal Discomfort Questionnaire and Cornell Hand Discomfort Questionnaire developed by the Human Factors and Ergonomics Laboratory at Cornell University were used on a sample of 140 office workers in a telecommunication company.MAIN OUTCOMES AND RESULTS: Discomfort/pain/ache at the wrist level was reported by 86.5% for the left side and 95.5% for the right side. Additionally, discomfort/pain/ache was reported by 77.5% of the sample for neck and 31% of the sample for the left and 50% for the right shoulder region. At the hand site, the area in the distal proximity of the wrist was the most affected site being indicated in 90% of cases for left side and 95% of cases for the right side.CONCLUSIONS: An overview of problems associated with the body parts in office work may allow targeted prevention and intervention.
To determine the functional capability in asymmetric trunk motion, isometric and isokinetic later... more To determine the functional capability in asymmetric trunk motion, isometric and isokinetic lateral flexion and axial rotation strengths of a normal and patient samples were measured. Seventy-three normal asymptomatic subjects (41 males and 32 females) and ten patients (9 males and 1 female) were tested. The dual objectives of the study were to develop a database for isometric and isokinetic lateral flexion and axial rotation strength capabilities of a normal sample and to determine the functional impairment of a sample of patients. More than 60% of low back injuries are associated with trunk twisting. Asymmetric motions are important risk factors. However, strength capability data for axial rotation are sparse and those for lateral flexion nonexistent. To achieve the objectives of the study, two devices were designed and fabricated. Isometric lateral flexion was tested bilaterally in neutral posture and at 10 degrees, 20 degrees, and 30 degrees of lateral bending. Isometric axial rotation was tested bilaterally in neutral posture and at 5 degrees, 10 degrees, 15 degrees, and 20 degrees of axial rotation. Isokinetic lateral flexion and axial rotation strengths were tested bilaterally starting from the neutral posture. The strength invariably declined progressively for all groups with increasing postural asymmetry. The strength in isokinetic activities ranged between 60% to 70% of the strength measured in isometric activities. All groups were significantly stronger in lateral flexion compared with axial rotation. The female sample ranged between 60% to 70% values of males for all activities studied. The patient group was weakest, ranging between 45% to 55% for isometric and 52% to 58% for isokinetic activities of their control group.
Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have s... more Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have suggested that dental professionals may suffer from musculoskeletal disorders (MSDs) of the low back and neck as well as other MSDs. This survey aimed to look deeper into MSDs among orthodontists and provide a starting point to direct ergonomic intervention. The standardized Nordic questionnaire was
To determine the functional capability in asymmetric trunk motion, isometric and isokinetic later... more To determine the functional capability in asymmetric trunk motion, isometric and isokinetic lateral flexion and axial rotation strengths of a normal and patient samples were measured. Seventy-three normal asymptomatic subjects (41 males and 32 females) and ten patients (9 males and 1 female) were tested. The dual objectives of the study were to develop a database for isometric and isokinetic lateral flexion and axial rotation strength capabilities of a normal sample and to determine the functional impairment of a sample of patients. More than 60% of low back injuries are associated with trunk twisting. Asymmetric motions are important risk factors. However, strength capability data for axial rotation are sparse and those for lateral flexion nonexistent. To achieve the objectives of the study, two devices were designed and fabricated. Isometric lateral flexion was tested bilaterally in neutral posture and at 10 degrees, 20 degrees, and 30 degrees of lateral bending. Isometric axial rotation was tested bilaterally in neutral posture and at 5 degrees, 10 degrees, 15 degrees, and 20 degrees of axial rotation. Isokinetic lateral flexion and axial rotation strengths were tested bilaterally starting from the neutral posture. The strength invariably declined progressively for all groups with increasing postural asymmetry. The strength in isokinetic activities ranged between 60% to 70% of the strength measured in isometric activities. All groups were significantly stronger in lateral flexion compared with axial rotation. The female sample ranged between 60% to 70% values of males for all activities studied. The patient group was weakest, ranging between 45% to 55% for isometric and 52% to 58% for isokinetic activities of their control group.
Isometric and isokinetic trunk flexion-extension strengths were studied among 73 subjects (41 mal... more Isometric and isokinetic trunk flexion-extension strengths were studied among 73 subjects (41 males and 32 females) and 10 patients (9 males and 1 female). The isometric strengths were measured in four postures of trunk flexion. The isokinetic trunk strengths were measured through the range of these postures. The study had two objectives: to develop a database for isometric flexion-extension strength at different levels of trunk flexion and isokinetic strength at corresponding angles and to determine the decrement in strength characteristics among patients of idiopathic low back pain. Though flexion-extension strength among normal subjects and patients has been studied, its variation due to standardized postural change has not been reported extensively. The influence of postural deviation on flexion-extension ratios are also largely unknown. To achieve the objectives of the study, a device flexion-extension-lateral flexion tester (FELT) was designed and fabricated. The male and female subjects performed isometric flexion and extension at 0 degree, 20 degrees, 40 degrees and 60 degrees of trunk flexion; and isokinetic flexion starting at neutral posture, and isokinetic extension starting at 60 degrees of trunk flexion. The patients performed isometric flexion and extension in neutral posture only; and isokinetic flexion-extension similar to normal sample. The average strength in each activity was between 70 and 80% of the corresponding peak strength. The isokinetic activity strengths ranged between 60 and 70% of the corresponding isometric activities in each group. The strength of females ranged between 60 and 70% of males. The ANOVA revealed that posture had a significant effect on strength. The multiple regression explained 73% of variance in isometric and 34% in isokinetic modes. A patient&#39;s strength profile should be determined in a posture that simulates activities of daily living to determine impairment and plan rehabilitation.
It is generally acknowledged that compensation payments (WCB) influence rehabilitation outcome in... more It is generally acknowledged that compensation payments (WCB) influence rehabilitation outcome in a negative manner. Patients receiving WCB have more treatment over a longer time period than their non compensated (NWCB) cohorts. It is not clear whether therapists (PT) perceive WCB clients as being more impaired and expect them to have a worse outcome than clients without WCB. The purpose of this study was to determine whether PTs&#39; clinical judgments are influenced by the knowledge of a patients WCB status and whether this knowledge influences their assessment findings or prognostic judgments. A convenience sample of 69 physical therapists (PTs) participated. Each PT viewed three videotaped assessments, of patients with low back pain (LBP) that differed in severity. The PT was provided with a brief history of the patient. Included in the history was a statement that the patient was (WCB group), or was not (NWCB group) in receipt of workers compensation benefits (WCB). The third group of PTs was given no information (control group) about the patient. PTs recorded physical assessment findings and made prognostic judgments about the patients. Data for the physical assessment findings and prognoses recorded by the PTs was analyzed across information groups using ANOVA. Knowledge of compensation status did not influence the PTs&#39; physical assessment findings but did influence prognostic judgments. WCB status was deemed to have a negative effect on outcome in patients with mild LBP. Additionally, NWCB status was deemed to have a positive influence on outcome in patients with severe LBP. The differences were most marked in the short term (1 month). It was concluded that PTs expectations of outcome are influenced by prior knowledge of compensation status.
International Journal of Industrial Ergonomics, 2003
So far, many different studies have examined possible implications of typing related posture and ... more So far, many different studies have examined possible implications of typing related posture and activity on carpal tunnel syndrome (CTS) incidence. Although they tend to present the findings as very apparent ones, assessing the complex relationships between the different causal factors implicated in keyboarding and in the usage of pointing devices, on the one hand, and work related upper extremity disorders (WRUED), especially CTS, on the other hand, is problematic. The aim of this review paper is to outline relevant information about CTS risk factors present in data entry task and their implications, with a special emphasis on different extreme postures determined by conventional and alternate keyboards, pointing devices and their role in the development of CTS. Secondly, a comparison of several keyboards with respect to design of keyswitch to reduce force and its effect on carpal tunnel pressure (CTP) is provided. This review critically considers the factors implicated in the occurrence of CTS due to computer work, analysing the determining factors from a well-considered perspective instead of considering them separate entities. Many ''ergonomic'' keyboards change the musculoskeletal region exposed to risk, instead of eliminating hazardous postures. The ergonomic assessment of new devices should precede their introduction and not follow it. Future research should be directed to establish a comprehensive understanding of what combinations of trigger factors should be eliminated or modified, to assess the impact of workstation redesign and to uncover the interrelationships between different factors that contribute to the development of CTS.
International Journal of Industrial Ergonomics, 2002
Theoretical assumptions become valid only when they are tested empirically. Whenever measurement ... more Theoretical assumptions become valid only when they are tested empirically. Whenever measurement instruments are used one needs to be sure that they yield accurate information for the construct of interest. This article outlines the measurement instruments properties and their impact on research as well as the differences and similarities between biases that could occur in different measurement and data collection procedures. Important criteria that must be met when developing a new measuring tool are presented in detail. The purpose of this review paper is to gather and organize the relevant information regarding measurement bias in research. It outlines important steps that will lead to a decreased error in measurement and data collection. As more and more ergonomic decisions are taken, based on the research outcome, the impact of the quality of measurement in various intervention programs becomes increasingly critical.
International Journal of Industrial Ergonomics, 2004
Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have s... more Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have suggested that dental professionals may suffer from musculoskeletal disorders (MSDs) of the low back and neck as well as other MSDs. This survey aimed to look deeper into MSDs among orthodontists and provide a starting point to direct ergonomic intervention. The standardized Nordic questionnaire was
International Journal of Industrial Ergonomics, 1994
Ten normal young adult females (mean age 26.8 years, mean weight 50.9 kg, mean height 165.9 cm) p... more Ten normal young adult females (mean age 26.8 years, mean weight 50.9 kg, mean height 165.9 cm) performed maximal and subjectively graded exertions of the stoop lift, hand grip, and finger pinch. The levels of graded exertion required were 80%, 60%, 40% and 20% of maximal voluntary contraction (MVC). The sequences of all conditions were fully randomized. Each of the randomized conditions was tried three times in succession. The entire experiment was carried out on four different days at the same time of the day on Monday, Wednesday, Friday of one week and Friday of the next week. The data obtained were subjected to descriptive and statistical analysis with t-test, analysis of variance, and correlation and regression. There were significant differences in the effort produced in three different activities (p < 0.01). The levels of exertion from 20% to 80% were all significantly different from each other (p < 0.01). However, there were no significant differences between the three trials of any given condition and the exertions produced on four different days. The 80% and 60% of exertions were overestimated and 20% was underestimated compared to the objective values based on MVC (p < 0.01). At 40% effort there was no significant difference between the objective level of exertion and subjectively gauged and produced effort for all three activities. The reliability of perception among the female subjects was similar for finger pinch, hand grip, and stoop lift activities.
International Journal of Industrial Ergonomics, 1991
Industrial activities are mediated through strength application. Physically demanding tasks are k... more Industrial activities are mediated through strength application. Physically demanding tasks are known to precipitate overexertion injuries. Therefore, this study was conducted to investigate the effect of posture on torque producing capability of the back. Fourteen volunteers (5 male students with mean age 25.4 yrs, mean height 178.3 cm and mean body weight 73.9 kg; 9 female students with mean age 20.8 yrs, mean height 165.9 cm and mean body weight of 56.1 kg) exerted their maximal isometric torque in lying, seated and upright postures. The lower body (hip down) was stabilized at the same places -hip, above and below knee, and at the ankle in all three postures. The subjects exerted their maximal voluntary effort for 5 seconds in attempted flexion, extension, and left and right lateral flexion. The sequence of test conditions was randomized. The torque produced in lying posture was significantly lower than those in standing or sitting postures (p < 0.01). They represented 35% to 61% of the standing posture in males and 46% to 53% among females. In all postures among both sexes extension torque was highest except men's standing flexion. The torque producing capability in lying posture was significantly less ( p < 0.01). The trunk torques of females ranged between 42% to 69% of males. Due to a large effect of posture on strength, a standardization of test postures is suggested for screening of industrial workers.
Postural and therefore biomechanical standardization in strength testing has not been rigorously ... more Postural and therefore biomechanical standardization in strength testing has not been rigorously and consistently applied. To develop a quantitative relationship between strength and posture (body position, symmetry, and reach) 30 normal subjects (18 male and 12 females) were required to stoop and squat lift or exert in the relevant posture against a standardized instrumented handle. The isometric lifting efforts and isokinetic lifts were studied. The isokinetic lifts were done at a linear velocity of 50cm/s of the hand displacement from the floor to the knuckle heights of the respective subjects in stoop and squat postures. The isometric stoop lifting efforts were exerted in two standardized postures: (a) with 60 degrees hip flexion; and (b) with 90 degrees hip flexion. The isometric squat lifting efforts were also exerted in two standardized postures: (a) with 90 degrees knee flexion; and (b) with 135 degrees knee flexion. All isometric lifting efforts and isokinetic lifts were performed at half, three-quarters, and full horizontal reach in sagitally symmetrical, 30 degrees left lateral, and 60 degrees left lateral planes. Isometric stoop and squat lifting efforts were also measured in self-selected optimal postures. These 56 conditions were tested in random order. The analysis of variance revealed that the gender, the mode of lifting, the postural asymmetry and reach of lifting affected the strength significantly (p less than 0.0001). Most two-way and three-way interactions were significant (p less than 0.01). Of 108 prediction regression equations, 103 were significant with up to 90% of the variation explained by anthropometric variables and sagittal plane strength. The reach affected the strength most profoundly followed by postural asymmetry and the mode of lifting.
Musculoskeletal disorders of back and neck among orthodontists are prevalent. Due to low instanta... more Musculoskeletal disorders of back and neck among orthodontists are prevalent. Due to low instantaneous load they have not been investigated. The present study aimed to quantify and compare instantaneous and cumulative loads on low back and neck in orthodontists. The sample included nine graduate orthodontic students from the University of Alberta and one practicing orthodontist to validate the generalization from student to professional group. The subjects were videotaped performing regular duties and the recorded postures were printed for biomechanical analysis of compression and shear loads and exposure time. Instantaneous loads were calculated using a biomechanical model developed specifically for this study and cumulative loads were calculated from the resultant loads. The average instantaneous low back compression loads for men and women were found to be 1383 N and 936 N respectively. The average daily cumulative load on the other hand were found to be 16.2 MNs and 9.9 MNs for males and females respectively. The study demonstrates that smaller loads cannot be ignored due to their magnitude if their duration is long because the time dependent properties of the tissues become modulating factor. Thus the measurement of instantaneous loads on tasks in orthodontists is not indicative of the amount of cumulative stress experienced by them.
Journal of Occupational Rehabilitation, Dec 1, 2001
This paper reviews the current state of knowledge regarding the tools used in evaluating the work... more This paper reviews the current state of knowledge regarding the tools used in evaluating the workplace and worker in hopes of preventing low-back injury. Information regarding the current state of expenditure and trends toward ergonomic intervention are discussed. Acknowledgment is made of the increasing shift of responsibility from Compensation Boards to industry, and a review proactive preventative strategies and medical knowledge is included. Current ergonomic assessment tools are reviewed and the role of the Physical Ergonomist is introduced. Suggestions are made regarding the value of current and future approaches in prevention and direction of research.
... Human muscle strength definitions, measurement, and usage" Part II -The scientific basis... more ... Human muscle strength definitions, measurement, and usage" Part II -The scientific basis (knowledge base) for the guide Anil MitaP'*, Shrawan Kumar ba Ergonomics and Engineering Controls Research Laboratory, College of Engineering, University of Cincinnati, Cincinnati ...
Http Dx Doi Org 10 1080 00140130500435595, Feb 20, 2007
The objective of this study was to determine the best variable, if any, to indicate the level of ... more The objective of this study was to determine the best variable, if any, to indicate the level of localized muscle fatigue. Six male and six female subjects were studied while they exerted their maximal voluntary contraction and 40% of maximal voluntary contraction of spinal extensors in an isometric lifting activity. The electromyography (EMG) of erectores spinae at thoracic and lumbar levels was measured bilaterally. Also, the muscle bed blood volume, level of blood oxygenation to erector spinae at L3 level and heart rate were measured. The initial and final values of subjective feelings of fatigue through visual analogue score, rate of perceived exertions and body part discomfort rating were recorded. The mean maximal voluntary contraction forces for males and females were 899 (238) N and 431 (135) N respectively. The mean durations of hold in maximal voluntary fatiguing contraction were 68.1 (39.9) s and 72.3 (37.0) s for men and women respectively. By the end of the hold the force declined to 52% for males and 62% for females. The EMG amplitudes and median frequencies also progressively declined (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). ANOVA revealed that the task percentile values of all variables were significantly different (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Gender had a significant main effect (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). The correlation coefficients between force and other individual variables were weak to modest, but significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). None of the single variables predicted fatigue reliably for either gender and levels of contraction. The regression equations developed were highly significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) and they explained 96 to 98% of variance in both genders and contractions.
Http Dx Doi Org 10 1080 00140139208967362, May 31, 2007
Despite numerous efforts to control occurrences of work-related low back pain, it continues to be... more Despite numerous efforts to control occurrences of work-related low back pain, it continues to be a significant problem. Since the causation of low back pain is under multifactorial control, it is suggested that the factor most vulnerable at any given time will determine the safety. Epidemiological, biomechanical, physiological, and psychophysical information presented in published literature has been analysed. The data available are related to injuries and the projected margin of safety. This paper therefore, is an integrative, inferential synthesis of the published work to discern the margin of safety. An attempt has been made to conclude, on the basis of objective evidence, an all encompassing criterion to ensure the safety of the back. The psychophysical approach appears to integrate biomechanical and physiological variables on a short term basis in the studies surveyed. However, it remains to be proven that the sensory conditioning due to prolonged and repetitive occupational tasks will remain responsive to cumulative load and fatigue failures.
International Journal of Occupational Safety and Ergonomics Jose, Feb 1, 2008
Two types of computer input devices, a conventional mouse and a roller bar one, were studied in t... more Two types of computer input devices, a conventional mouse and a roller bar one, were studied in terms of muscular activity in m. trapezius dexter, m. deltoideus anterior dexter and m. extensor digitorum dexter, and comfort rating. Fifteen university students and employees participated in this study. The order of the devices was random. While a task was performed, electromyography (EMG) data were recorded for each test. Muscular activity was found to be significantly lower for the roller bar mouse than for the conventional one. Comfort rating indicated there was a significant difference in moving a cursor with the conventional mouse compared to the roller bar one. It is concluded that a roller bar mouse allowed the subjects to work closer to the body compared to the conventional one, thus the former can be recommended as a general means of reducing upper extremity musculoskeletal disorders.
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