The effect of individually adjusted workstations on upper quadrant posture and muscle activity in school children

Evidence suggests there is increasing use of computers by children and poor workstation designs for children. This laboratory study investigated the effect of adjusting computer display height and desk height on upper quadrant posture and muscle activity. Thirty three children aged 4-17 years worked on a desktop computer at a standard school workstation and at a workstation adjusted to the individual, typically consisting of a lower display and desk height. The adjustments resulted in increased head tilt, neck flexion, gaze angle, cervical erector spinae activity and a trend for lower right upper trapezius activity. The recent evidence that suggests more head and neck flexion is not necessarily worse is discussed and normative values for children's head tilt and neck flexion presented. The role of forearm support in decreasing trapezius activity is also discussed.     

The effects of a continuous passive motion device on myoelectric activity of the erector spinae during prolonged sitting at a computer workstation

Continuous passive motion (CPM) has been proposed as a method to help individuals with low back pain cope with prolonged sitting. The purpose of this study was to investigate the effects that a commercially available CPM device had on lumbar and thoracic erector spinae (ES) muscle activation (using surface electromyography, "EMG"), and on subjective discomfort during prolonged seated computer work with and without the use of the CPM device. There were no significant differences in average ES muscle activation levels, amplitude probability distribution functions, and EMG gaps number and length when sitting with the CPM device was compared to sitting normally. Subjective ratings of discomfort were also not significantly different between the two sitting conditions. The results indicated that there were no clear mechanisms by which the CPM device may reduce ES muscle pain and fatigue for the tasks and pain-free individuals studied.     

Level of self-reported neck/shoulder pain and biomechanical workload in cleaners

The aim of the present study was to investigate the relation between self-reported pain, muscular activity and postural load during cleaning tasks. Eighteen cleaners performed usual cleaning tasks in both a laboratory and a lecture room. The level of perceived pain in the neck-shoulder region during the last 7 days was recorded. Bipolar surface electromyography (SEMG) was recorded bilaterally from upper trapezius and erector spinae muscles during cleaning. Root mean square (RMS) and permutation entropy (PE) values representing amplitude and complexity of SEMG time-series were estimated. A tri-axial accelerometer package was mounted on the low back (L5-S1) to measure postural changes during cleaning tasks. The 10th, 50th and 90th percentiles of the angular distributions were computed to characterize postures and movements. Pain tended to play a significant role on RMS of left/right trapezius and left erector spinae muscles (P≤0.08). Cleaners with low pain level exhibited higher muscular activity during cleaning. Pain played or tended to play a significant role on PE of left and right erector spinae muscles (P≤0.08). Pain played a significant role on the 10th, 50th and 90th percentile (P<0.05) of lateral flexion angle (side bending). The present study emphasizes biomechanical adaptations occurring in presence of neck-shoulder pain during cleaning tasks.     

Stationarity test of electromyographic signals during isokinetic trunk exertions

The aim of this study is to investigate the stationarity of the electromyographic (EMG) signals during isokinetic exertions of the trunk muscle. Six healthy subjects participated in this study. The erector spinae muscles were used to collect the signals. In order to simulate the isokinetic exercises of the trunk, a Cybex system with a trunk modular component was used. All subjects performed sustained exertions with a combination of load (25%, 50% MVC) and angular velocity (0, 15, 30 degree/s). The stationarity of the signals was tested by the reverse arrangements test and modified reverse arrangements test. In the results, the signal stationarity was high in all conditions in the reverse arrangements test. However, in the modified reverse arrangements test it was relatively low at about the 30 degree/s angular velocity. In the analysis of variance, the effect of angular velocity was statistically significant at the 0.05 significance level in the modified reverse arrangements test and Tukey's HSD grouping showed that the stationarity of 30 degree/s angular velocity was significantly different from 0, 15 degree/s condition. These results indicate that the stationarity of the EMG signals showed no difference between isometric and isokinetic conditions when the angular velocity was equal to 15 degree/s.     

Application of discriminant analysis-based model for prediction of risk of low back disorders due to workplace design in industrial jobs

The occupational exposure limits of different risk factors for development of low back disorders (LBDs) have not yet been established. One of the main problems in setting such guidelines is the limited understanding of how different risk factors for LBDs interact in causing injury, since the nature and mechanism of these disorders are relatively unknown phenomena. Industrial ergonomists' role becomes further complicated because the potential risk factors that may contribute towards the onset of LBDs interact in a complex manner, which makes it difficult to discriminate in detail among the jobs that place workers at high or low risk of LBDs. The purpose of this paper was to develop a comparative study between predictions based on the neural network-based model proposed by Zurada, Karwowski & Marras (1997) and a linear discriminant analysis model, for making predictions about industrial jobs according to their potential risk of low back disorders due to workplace design. The results obtained through applying the discriminant analysis-based model proved that it is as effective as the neural network-based model. Moreover, the discriminant analysis-based model proved to be more advantageous regarding cost and time savings for future data gathering.     

Assessment of physical exposures and comparison of exposure definitions in a repetitive sawmill occupation: trim-saw operator

This paper describes the physical exposures required to perform a sawmill job associated with a high incidence of upper extremity musculoskeletal injury. Exposure variables are described by multiple posture, exertion and frequency definitions and the comparability of those definitions are examined. Effective industrial prevention efforts require an accurate assessment of risk. Surface electromyography and electrogoniometry were used to quantify the physical exposures of 29 trim-saw operators in four sawmill facilities. Average wrist ranges of motion of 32, 57 and 58 degrees in wrist radial/ulnar deviation, flexion/extension and pronation/supination respectively were required to perform the job. Defining wrist range of motion by the peak postures observed versus those required to perform the primary task resulted in significantly different ranges of motion (p<0.05). Job performance required an average of 33% of maximum voluntary contraction. Repetitions per day ranged from 3,549 to 14,460. Percentage of maximum voluntary contraction was not associated with psychophysical measures of exertion.     

Spinal disc hydration status during simulated stooped posture

Stooped work has been shown to be associated with the development of low back disorders, particularly those that affect the spinal intervertebral discs. Although several studies have been conducted to evaluate the effects of physical factors on disc health, little research has focused on the effect of prolonged stooped work on disc hydration- a critical component of disc health. The purpose of this study is to explore the connection between stooped work and low back pain through controlled mechanical loading and quantitative analysis of disc hydration during in vitro simulated stooped and erect loading conditions of porcine discs. The results showed that stooped postures exhibit significantly decreased overall water content relative to erect postures. Since as disc hydration forms the foundation for overall disc health and proper function, these results have implications for the injury mechanisms associated with stooped work.     

Ergonomic evaluation in a values transportation company in Venezuela

The objective was to analyze the work activity and identify risk factors that could account for musculoskeletal disorders in the upper extremities, shoulder and neck of workers of a transport values company in Venezuela. The methods used were: collective interview, tasks observation, evaluation of posture with RULA method and evaluation of repetitive motions with the OCRA method. Five workstations were evaluated. Main problem perceived by workers was: exposure to chemical and biological hazards when handling paper money and coins; inadequate chairs and close supervision. The postures level risk was 1 or 2 for the RULA scale. Only two workstations showed ligth and medium risk level by OCRA method. Conclusion: The factors identified that could explain the musculoskeletal changes were: wrist repetitive flexion and extension, shoulder elevation, lifting weight above shoulder height, elbow repetitive flexion and extension, neck flexion, extended work journey, work overload, high responsibility and strict supervision by a video camera.     

Postural assessment of school children: an input for the design of furniture

During the last decades of the previous century, school desks with a tilt top have disappeared. The chairs have been designed for sitting upright, with the hip, knees and ankles all at right angles. However, the erect posture cannot be maintained for more than one or two minutes, after which it will result in fatigue, discomfort or poor posture. The main aim of project is to identify the type of furniture that most effectively contribute to adequate neck and back postures of the school children, by carrying out a postural analysis of a sample of school pupils when using three different types of furniture. The postures adopted by school pupils were monitored by video during several activities, such as reading, writing and painting tasks, copying from a blackboard and listening the teacher. Additionally, the characteristics of the adopted postures were assessed by registering the head tilt, flexion of the neck, trunk and hips position. All these aspects were classified and the results were recorded for future analysis. The obtained results seem to point out that the use of a school desk with a tilted table surface resulted in a reduction in trunk and neck flexion, preserving the natural lordosis in the lumbar and cervical regions. Accordingly, it can be concluded that there are alternatives to consider in the furniture design in order to eliminate tensions and, consequently, to improve children's wellbeing.     

Elbow torque ellipses: investigation of the mutual influences of rotation, flexion, and extension torques

Most strength tests are restricted to measuring joint torques only in main directions like flexion or pronation. However, for an advanced strength prediction model, information about maximum possible joint torques in intermediate directions also has to be known. This paper concentrates on obtaining functions for maximum joint torques in arbitrary directions in the elbow. Therefore, isometric joint torque measurements have been conducted with 20 young males applying joint torques in eight different directions in one posture (90 degrees elbow flexion, 0 degrees shoulder flexion, neutral forearm rotation). It turns out that the appearance of the resulting shape can be best predicted using ellipse segments. Furthermore, a standardized ellipse could be obtained for the measurement posture. This helps to predict maximum joint torques in any other direction by knowing only one of the main joint torques.     

Biomechanical modelling and evaluation of construction jobs for performance improvement

Occupational risk factors, such as awkward posture, repetition, lack of rest, insufficient illumination and heavy workload related to construction-related MMH activities may cause musculoskeletal disorders and poor performance of the workers, ergonomic design of construction worksystems was a critical need for improving their health and safety wherein a dynamic biomechanical models were required to be empirically developed and tested at a construction site of Tata Steel, the largest steel making company of India in private sector. In this study, a comprehensive framework is proposed for biomechanical evaluation of shovelling and grinding under diverse work environments. The benefit of such an analysis lies in its usefulness in setting guidelines for designing such jobs with minimization of risks of musculoskeletal disorders (MSDs) and enhancing correct methods of carrying out the jobs leading to reduced fatigue and physical stress. Data based on direct observations and videography were collected for the shovellers and grinders over a number of workcycles. Compressive forces and moments for a number of segments and joints are computed with respect to joint flexion and extension. The results indicate that moments and compressive forces at L5/S1 link are significant for shovellers while moments at elbow and wrist are significant for grinders.     

Occupational lifting tasks as a risk factor in low back pain: a case-control study in a Mexican population

The objective of this study was to quantify and assess whether lifting tasks in the workplace are a risk factor in lumbar spondyloarthrosis etiology. A case-control study was performed with 231 workers, 18-55 years old, insured by the Mexican Social Security Institute (IMSS, according to its designation in Spanish). A multivariate analysis using conditional logistical regression showed that lifting tasks, combined with driving tasks, are associated with this illness (OR = 7.3; 95% CI 1.7-31.4). The daily frequency of lifting as it interacts with work as a driver resulted in a greater risk (OR = 10.4; 95% CI 2.0-52.5). The load weight, daily task-hours and cumulative time showed a dose-response relationship. The attributable risk for lifting tasks was 0.83, suggesting that 83% of lumbar spondyloarthrosis development could be prevented if risk factors were eliminated by ergonomic redesign of the task.     

Prevalence of the metabolic syndrome and its relationship with diabetes mellitus by aging

Abstract

Introduction.?It is important to make a prompt diagnosis of metabolic syndrome (MetS) in order to prevent the development of cardio-/cerebro- vascular diseases and diabetes mellitus (DM). The authors estimated the risk of development of DM by the presence/absence of MetS and age groups.

Methods.?A cross-sectional study of subjects undergoing intensive health examination was conducted (3149 men aged 30–69 years). Diagnosis of MetS was based on the criteria of the National Cholesterol Education Program Expert Panel (NCEP).

Results.?The prevalence of DM occurring in association with MetS increased with age; it was 11.9% in subjects with MetS in their 30s, it was 19.8% in subjects with MetS in their 60s. The prevalence of DM among subjects who had one or two components of MetS also increased with age. There was a significant progressive increase of the odds ratio in subjects in their 30s, 40s, 50s and 60s who were judged as having MetS; significant increase of the odds ratio was seen in subjects in their 60s, even in those who were not judged as having MetS.

Conclusions.?Subjects with MetS show a high prevalence of DM, and the prevalence increased with age in the subjects.     

The effects of distance and individual differences in arousability on nonverbal involvement: A test of discrepancy-arousal theory

Mutual influence in human interaction refers to the tendency for persons to alter their verbal, vocal, and kinesic behaviors in response to the intensity, frequency or duration of those behaviors emitted by their partners. Numerous explanations of these processes have been put forward involving principles of approach-avoidance conflict, arousal, reward, and cognitive processes. These explanations are reviewed with special attention given to an arousal based theory, discrepancy-arousal. This theory holds that mutual influence is primarily the result of arousal changes due to the degree of discrepancy of partner's behavior from the receiver's expectation.The theory predicts that persons who differ in reaction to arousal should also differ in their response to a partner's immediacy. This hypothesis was tested on high and low sensation seekers under conditions of near and normal distances during an interview. Several different behavioral responses were coded, including eye gaze, posture and orientation, smiles and laughter, object- and body-focused gestures, vocalization, pauses, and latencies to respond. The hypothesized interaction did not materialize with a median split on sensation seeking. A measure of state-trait sensation seeking (STSS) was developed. The interaction between distance and a median split on the state-trait measure was significant for eye gaze and posture and orientation, with the high STSS subjects compensating less than the low STSS subjects.     

Suicide risk and exposure to mobbing

The aim of this study was to study suicide risk in subjects exposed to mobbing, that is, systematic psychological harassment in the workplace. Such psychological harassment, unique to the workplace, threatens both the emotional well-being and professional ability of its victims. The items of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) that assess suicide risk were studied in 102 individuals who were exposed to mobbing. The results indicated that individuals exposed to mobbing had clear differences on the MMPI-2 from normative samples. In addition, those who appeared to be at risk for suicide differed in their scores from those not at risk. Implications for psychopathology and suicide preventions are discussed.     

Motivational Factors Affecting Patient Attrition in a Weight Reduction Program

Abstract

The study hypothesizes that the greater the satisfaction of a patient's basic motivational needs, the greater the likelihood that the patient will complete the program. Patients were given a self-report questionnaire to assess the strength of their basic motivational needs as they entered the program; and a Likert-type questionnaire concerning satisfaction of needs as they left the program. The results show that those who completed the program experienced greater satisfaction of needs than those who did not complete the program. Analysis of covariance of completion of the program and need satisfaction was significant (p < .01) thus supporting the hypothesis.

“Long-term Oral Contraceptive Use and the Risk of Breast Cancer,” THE CENTERS FOR DISEASE CONTROL CANCER AND STEROID HORMONE STUDY. Using oral contraceptives for long periods or using them when one has other risk factors has been hypothesized to increase the risk of breast cancer. To study these issues, we analyzed data from a multicenter, case-control investigation—the Centers for Disease Control's Cancer and Steroid Hormone Study. All women 20 to 54 years old with a first diagnosis of breast cancer ascertained by eight population-based cancer registries are study subjects; controls are selected at random from the general population of these eight areas. Analysis of the first 689 cases and 1,077 controls studied showed that women who had used oral contraceptives at some time in their lives had a relative risk of 0.9 compared with never-users (95% confidence interval, 0.8 to 1.2). Neither duration of oral contraceptive use nor time since first use altered a user's risk of breast cancer; women whose first use was more than 15 years ago and who used oral contraceptives for 11 years or more had a relative risk of 0.8 (0.5 to 1.4). Oral contraceptive use did not increase the risk of breast cancer among women with benign breast disease or a family history of breast cancer. Oral contraceptive use before a woman's first pregnancy did not increase her risk of breast cancer significantly more than other methods of delaying first pregnancy. This study provides no support to the hypothesis that oral contraceptive use increases a woman's risk of breast cancer. (Journal of the American Medical Association 1983;249:1591–1595.)

“Oral Contraceptive Use and the Risk of Ovarian Cancer,” THE CENTERS FOR DISEASE CONTROL CANCER AND STEROID HORMONE STUDY. Since oral contraceptives have been used by more than 40 million American women, an association between oral contraceptives and ovarian cancer could have a substantial public health impact. The Centers for Disease Control, Atlanta, is studying this relationship as part of a multicenter, case-control study—the Cancer and Steroid Hormone Study. During the first ten months of the study, we enrolled 179 women aged 20 to 54 years who had been ascertained to have newly diagnosed ovarian cancer by eight population-based cancer registries. From the general population of those eight areas, we selected as controls 1,642 women with intact ovaries. Users of oral contraceptives had an age-adjusted risk of ovarian cancer developing of 0.6 relative to those who had never used them (95% confidence interval, 0.4 to 0.9). The risk of ovarian cancer decreased with increasing duration of oral contraceptive use and remained low long after cessation of use. These results were not accounted for by parity, infertility, or other potentially confounding factors. We estimate that more than 1,700 cases of ovarian cancer are averted each year by past and current oral contraceptive use among women in the United States. (Journal of the American Medical Association 1983;249:1596–1599.)     

Relationship between construction workers' musculoskeletal disorders and occupational health service activities

Construction work consists of numerous factors that influence workers' occupational health and that load the musculoskeletal system in particular. Musculoskeletal disorders are responsible for over a third of all sick leaves lasting over nine days in the construction industry. Occupational health services (OHS) were organized for 85% of the construction workers in our study. The proportion of construction workers who had suffered from chronic or repetitive neck and shoulder, shoulder or arm, or low-back disorders was 55.6%, 44.8% and 42.1%, respectively. Those who felt that they had received enough information, advice or guidance from OHS concerning work posture, work performance or work tools were more often those who had not suffered from shoulder or arm disorders (60.9% vs. 39.1%, p=.024, respectively) or low-back disorders (63.6% vs. 36.4%, p=.034, respectively) during the last month than those who had. Those who had received enough support from OHS concerning maintenance of work ability were more often workers who had not suffered from low-back disorders during the last month than those who had (63.3% vs. 36.7%, p=.004, respectively). OHS should focus more on workers who would really benefit from their activities at a particular time and in a particular situation (primary, secondary or tertiary prevention) and who are themselves devoted to improving their health.     

Notebook computer use with different monitor tilt angle: effects on posture, muscle activity and discomfort of neck pain users

This study aimed to evaluate the posture, muscle activities, and self reported discomforts of neck pain notebook computer users on three monitor tilt conditions: 100°, 115°, and 130°. Six subjects were recruited in this study to completed typing tasks. Results showed subjects have a trend to show the forward head posture in the condition that monitor was set at 100°, and the significant less neck and shoulder discomfort were noted in the condition that monitor was set at 130°. These result suggested neck pain notebook user to set their monitor tilt angle at 130°.     

Musculoskeletal symptoms among dentists in relation to work posture

OBJECTIVE: To determine the effect of work posture on musculosketal complaints in Israeli dentists. METHODS: The population included 60 male dentists mean age was 46.0 (+/- SD 8.66), 30 worked in sitting position and 30 were altering positions. Study population completed the standardized Nordic questionnaire and informative form concerning recipient's practice of dentistry, bio-demographic variables and questions about workloads. RESULTS: Musculoskeletal symptoms in the last 12 months were localized primarily in the lower back and in the neck (55% and 38.3% respectively). There was a significant correlation between the time spent sitting and the severity of low back pain (r = 0.41, p = 0.01). On the other hand there was no significant correlation between time spent sitting and other musculoskeletal complaints (r = - 0.16). CONCLUSIONS: Dentists who work in the sitting position have more severe low back pain than do those who alternate between sitting and standing despite the fact that those who sat at least 80% of the time worked less hours and had less of a workload during their working hours. This suggests that altering position should be recommended to dentists. An intervention study, however, is needed to demonstrate that changing posture will decrease the prevalence of low back pain in dentists.     

Heart disease risk perception in college men and women

The authors sought to assess the perception of risks for coronary heart disease (CHD) in college men and women. They surveyed 470 undergraduates from 2 major 4-year institutions who completed a questionnaire that measured perceived risks for heart disease. Sixty-eight percent of the respondents rated their risks as lower or much lower than those of their peers, indicating a clear optimistic bias. The research also revealed that the students who exercised regularly rated their risk of coronary disease lower than those who did not do so. In addition, women perceived a number of risk markers to be more potent or causative factors than men did. A significant number of participants did not comprehend commonly understood causal relationships associated with heart disease risk. The findings in this preliminary investigation suggest that college men and women do not accurately perceive their risks for developing heart disease.