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Ergonomics and Body Mechanics in the Work Place
Abstract
Ergonomics in the work place has become more critical in recent years, both from a sedentary and a dynamic perspective. As mentioned, overall work-place injuries have decreased, but carpal tunnel disease has risen steadily. It is essential that health care providers understand the basis of ergonomics to ensure quality of care to the injured worker as well as to promote safe work practices.
The field of ergonomics has had more concrete scientific evidence from which to draw conclusions than body mechanics. Health care providers are able to make an assessment of a work station and have clear scientific evidence to support their rationale to change that work station.
The controversy still goes on regarding the correct position the spine should assume when one attempts to lift. Only with continued basic scientific research will we solve that dilemma.
... Pain management � Utilization of techniques such as posture and body mechanics education, ergonomic modifications, heat/cold therapy, and electrical stimulation � Aims to reduce inflammation, promote healing, and provide relief from discomfort [110][111][112][113] Functional mobility and independence � Assessment and addressing of limitations in mobility, strength, and endurance � Enables individuals to regain independence in activities of daily living (ADLs) and instrumental activities of daily living (IADLs) such as dressing, bathing, cooking, and household chores [114][115][116] Ergonomic adaptations � Evaluation of work and home environments to identify risk factors that may exacerbate sciatica symptoms � Provides recommendations for ergonomic modifications such as proper seating, workstation adjustments, and assistive devices to reduce strain and promote proper body mechanics [117][118][119][120] Activity modification and pacing � Guidance for individuals in modifying activities to accommodate their limitations and gradually increase participation � Education on pacing techniques to prevent overexertion and manage fatigue [121,122] Education and self-management � Education on body mechanics, posture, stress management, and lifestyle modifications � Empowerment of individuals with knowledge and self-management strategies to prevent future flare-ups and promote overall health [123] Psychosocial support � Addresses the psychosocial aspects of chronic pain conditions like sciatica � Offers coping strategies, stress management techniques, and support to enhance overall well-being and quality of life [124][125][126] THAKUR ET AL. ...
Sciatica is a severe form of pain caused by compression of the sciatic nerve that radiates from the back toward the hip and outer side of the leg. Conventional treatments for sciatica include pain medication, physical therapy, and surgery in severe cases. However, these approaches can be invasive and costly and may not provide long‐term relief. Occupational therapy refers to the intentional and strategic application of various activities associated with daily life, work, education, and leisure to address functional impairments. Focusing on targeted exercises, manual techniques, and ergonomic modifications to alleviate symptoms and improve function, it offers a promising alternative to medical treatments. Occupational therapy interventions for sciatica can reduce pain, increase mobility, and enhance the overall quality of life. As an empowering approach, such techniques aid symptom management and functional independence. This article explores occupational therapy‐based assessments, interventions, outcomes, progress tracking, pharmacotherapy, challenges owing to surgical approaches, and devices for sciatic pain rehabilitation, with assessments aimed at improving the overall quality of life for individuals affected by this condition. Future research should focus on developing and validating new assessment tools and outcome measures specific to sciatica, enabling more accurate evaluation and progress monitoring.
... This way of life is directly related to the increased risk of developing the disease, the most common of which is the degeneration of the musculoskeletal system (11). Regardless of the work performed at the workplace, each position of the body or extremity causes a certain load of the corresponding physiologic functions of the worker (12). In the sitting position, due to the long-lasting static contraction of the spinal cord extender muscle, their excessive fatigue occurs and the end result is the spasm of the muscles and severe pain (13). ...
Aim To determine a degree of change in the bones of workers who spend their full time job in sitting position and to find a correlation between smoking and changes in bone structure. Methods Examinees were 213 female workers who worked full time sedentary work in front of computer. Each worker was subjected to physical examination and ultrasonic osteodensitometry of calcaneus.
Results The average age of patients was 45.4 years. Changes in bone density were found in 110 (51.64%) workers. Correlation between smoker and non-smoker groups was positive, but “r“ was higher in smokers than in non-smokers. It is worrying that 10 out of 22 persons in the group up to 30 years of age have osteopenia.
Conclusion Recommendation for regular annual control of bone density of the working group at risk regardless of age should be followed. Prescribing exercise for the working group at risk should be a significant part of preventive work in clinics of occupational medicine and sports.
... Thus, there is a need for physiotherapists to create awareness and offer prevention measures of back injury to the general population. The approach of patient education should also include ergonomic principle and body mechanics in work place 11 . This knowledge for health care providers can provide the basis of ergonomics to ensure quality care. ...
Low back pain (LBP) is a major medical and social problem associated with disability and work absenteeism. Since the effect on unawareness on back care among hospital staff may affect the smooth running of the services to the public and patients, it is the objective of this study to identified the awareness of back care among nurses so that preventive measures can be taken. About 80 nurses working in the outpatient clinic was survey using self addressed questionnaires which were adapted from Zutphen Physical Activity Questionnaire at Queen Elizabeth Hospital, Kota Kinabalu. Demographic analysis demonstrated that among the eighty nurses that responded, 37.5% (n=30) are Malays, 25% (n=25) Chinese and 37.5% (n=30) (to include other Sabahan tribes). Their age group varies between 23 to 55 years of age. A total of 72 nurses, both agreed (45%,n=36) and strongly agreed (45%,n=36) that understanding good postures is important to prevent LBP. They felt strongly (55%, n=44) about the importance of correct lifting techniques, and having a well-designed workplace (50%,n=40). Regarding factors that cause LBP, 55% (n=44) of them strongly agreed that good lifting technique can prevent LBP while 56 (70%) agreed that prolong sitting doing computer work can cause LBP. About 60% (n=48) also agreed that LBP can cause stress and that 45% (n=36) of them strongly agreed that being overweight than average can worsen LBP. However, 40% (n=32) provide a neutral answer to whether height have any influence on LBP while 50% (n=40) agreed that weak back muscles can worsen the backache further. However, 45% (n=36) agreed that games that involved back movement have high risks and 55% (n=44) agreed that swimming helps to strengthen back muscle. The environmental factors addresses issues of footwear and soft mattress where 60%(n=48) agreed while 15%(n=12) strongly agreed that good footware and appropriate use of soft mattresses 60% (n=48) can prevent LBP. This study have demonstrated that the nurses that participated had a clear understanding and knowledge on back care even though a wider study need to be carried out to ensure validity of study finding.
... However, to effectively manage these problems, it is important to understand all of the factors including age, presence of systemic disease, physiologic predisposition, work behaviors, type of job, and ergonomic design of equipment. 7 Musculoskeletal disorders in health professionals have been extensively documented. By far the largest body of work related to MSDs and health care professionals is in the dental and laparoscopic surgery fields. ...
... Correct strategies in body mechanics should be used while lifting, pushing, pulling or transferring a mass, such as an object or person. Numerous studies have attempted to define the optimal ergonomic arrangements and body mechanics during these functional tasks (Gassett, Hearne, & Keelan, 1996;Luepongsak, Krebs, Olsson, Riley, & Mann, 1997;Sparto, Parnianpour, Reinsel, & Simon, 1997;Wollenberg, 1989). ...
Thesis (Ph. D.)--Texas Tech University, 2002. Includes bibliographical references (leaves 179-203).
... He also noted the use of a-mouse has been shown to increase time in static and in extreme posture, and has increased biomechanical torques (Karlquist, 1996). Gassett et al. (1996) recommended the computer mouse be located at the level of the keyboard, close to the body, and the operator's proximal (shoulder) muscles move the forearm while maintaining a neutral wrist position. Pascarelli and Kella (1993;Pascarelli, 1999).) ...
There is a high risk of musculoskeletal discomfort and injury due to the lack of professional guidance and training in caregiving postures. This study aimed to develop a risk assessment and visualization method by analyzing caregiving postures. Participants with (n = 8) and without (n = 10) caregiving experience were recruited to simulate patient transfer from bed to wheelchair. The Rapid Entire Body Assessment (REBA) method lacked sensitivity in distinguishing the experienced and inexperienced groups. We found that the visualization of the center of gravity (COG) trajectory could represent distinct posture differences between the two groups. Based on this finding, we considered a modified REBA method combining the COG trajectory, load-bearing time, and asymmetric load parameters, named the Caregiving-REBA (C-REBA) method. Our results demonstrated that C-REBA could effectively distinguish experienced and inexperienced caregivers, especially in caregiving task Stages 2–4. In conclusion, the present work explored adjusting to the parameters of the REBA method. The proposed C-REBA method could be easily imbedded into the Internet of Things (IoT) device to assess the caregiving posture for providing visual guidance and warning of the risk of discomfort or injury.
Microscope work is straining both the visual and the musculoskeletal systems. Many ergonomic risk factors are presented in the microscope work for musculoskeletal system complaints. Awkward and static posture, high repetition, contact stresses and working for a prolonged time are the risk factors. A survey investigating musculoskeletal pain and ergonomic arrangement was developed and sent to pathologists who work in various hospitals in İzmir and the cities nearby to investigate the frequency of musculoskeletal problems and its relationship with some ergonomic factors and duration of work in pathologists. Neck, upper back and finger pain was significantly higher in subjects who worked more than 4 hours a day when compared with subjects who work less than 4 hours. The effects of microscope work on the occurrence of musculoskeletal disorders should be taken seriously in pathologists.
Erudition of clinical "skills" used by manually trained physical therapists involves the complex domain of cognitive, affective, and psychomotor concepts. The purpose of the study was to obtain consensus among manual therapy educators regarding stand-alone skills required during competent application of manual therapy and to distill these stand-alone skills into smaller but more homogeneous skill sets. Eighty manual therapy educators in entry-level and post-entry-level educational programs completed a three-round Delphi survey aimed at developing consensus among experts in the field regarding the stand-alone skills that are important to a learners' development of manual therapy competencies. From the Delphi outcomes, a principal component factor analysis distilled eight component skill sets that were associated with orthopedic manual therapy (OMT) proficiency: (1) manual joint assessment, (2) proficiency of fine sensorimotor characteristics, (3) manual patient management, (4) bilateral hand-eye coordination, (5) manual gross characteristics of the upper extremity, (6) manual gross characteristics of the lower extremity, (7) control of self and patient movement, and (8) discriminate touch. Manual joint assessment comprised 46% of the factor analysis variance and contained the majority of stand-alone descriptor statements from a Delphi survey. This study found that despite the disparate backgrounds among respondents, the eight skill sets were identified as important to OMT competency and application. By identifying the key skill sets required for OMT competency and application, OMT educators may more effectively identify teaching methods associated with improved educational outcomes.
The objective of this study was to evaluate the effects of regular stretching exercises on pain associated with working at a computer workstation, and to ascertain whether the type of media used for exercise instruction had an effect on outcomes.
Sixty-eight volunteers were divided into three equivalent groups. All of the subjects worked at computers for prolonged periods of time and reported that their pain had been a source of distress for at least three weeks prior to the intake evaluation.
A pretest-posttest-control group design with cluster randomization was used to evaluate the effect of a stretching program on pain. Thirty-six different stretches were performed by the subjects for 15-17 work days. Two intervention groups were directed to stretch once every six minutes. One group (n=22) was reminded to stretch via a computer program, the second group (n=23) by using a hard copy version of the stretches with pictures and written instructions, and a third group received no intervention.
ANOVA analysis found a significant reduction in pain of 72% (p < 0.001) for the computer-generated stretching program, and of 64% (p < 0.001) using the hardcopy version of the intervention. The control group had an increase in pain of 1%.
Both software and hard copy stretching interventions contributed to a decrease in pain without making any changes to workstation ergonomics and there was no significant statistical difference in the outcomes of either intervention. The subjective evaluation of pain using both visual analog scales and a newly created "pain spot" assessment technique yielded similar results.
Thesis (doctoral)--Wageningen Universiteit, 2001.
This article describes the magnitude, extent, and economic consequences of some of the more common, work-related musculoskeletal disorders. In addition, it provides a brief historic overview of the state-federal vocational rehabilitation program in the United States. It identifies and considers a constellation of risk factors for work-related disability because of musculoskeletal disorders, and it discusses phases of physical rehabilitation as that process relates to injured workers. The shifting disability paradigm is examined, and attention is given to terminology that has become fashionable since passage of the landmark Americans with Disabilities Act of 1990. Finally, various factors and conditions that often become barriers to an injured person's successful return to the workforce are briefly discussed.
This work evaluates the imposition of managed care techniques on the rate of claims and surgeries utilizing a pre- versus post-program analysis. The purpose was to ascertain whether managed care techniques--specifically, an ergonomic program, medical treatment guide-line, nurse case management, and utilization of a preferred provider organization consisting of academic physicians--would reduce the rate of the claims and surgery in a population of predominantly health care and university workers. The claims frequency rate and surgical frequency rates per 1,000 employees and per 1,000 claims was significantly lower during the managed care period than during the year prior to the initiation of managed care. The distribution of surgical procedures, as well as the duration of disability in the years of injury, after the initiation of managed care (1993-1997) were different from those same parameters in the fiscal years prior to the initiation of managed care (1990-1992). The results suggest that even in the workers' compensation environment, where financial incentives encourage a higher claims and surgical frequency rate than do the fee-for-service or prepaid medical environments, managed care techniques can be successfully utilized. A unique feature of the study was the use of university-based physicians as a specific managed care technique to influence surgical rates.
We studied the contribution of physical load in daily activities, including activities in work, housekeeping, and leisure time, to the burden of low back problems (LBP) in the population.
Logistic regression models were used to calculate the association between physical load and several LBP parameters as assessed by questionnaire in a cross-sectional study on 22,415 randomly selected men and women in The Netherlands, controlling for well-known LBP determinants. The population attributable risk (PAR) percentage was estimated with the elimination method using the logistic model.
Half of the population reported LBP during the past year and 19% chronic LBP. Activities characterized by an awkward posture, by the same posture for a long time, or by often bending and rotating the trunk increased the risk for LBP, with ORs between 1.1 and 1.6. More than 13% of the 1-year prevalence of LBP could be contributed to these activities. This PAR was higher for those belonging to the working population, for women, and for the more severe LBP parameters.
Because LBP present such a large public health problem, the estimated potential impact of eliminating (the unhealthy effect of) physical load is substantial. To assess the real health gain, more insight is necessary into the causality of the relationship and into effective preventive measures.
{\it Objectives:} The purpose of this study was to determine whether individuals with work-related injuries receiving worksite analysis would have less lost workdays than individuals not receiving worksite analysis. Therapeutic management of work-related injuries in a hospital and a university setting were also compared.
{\it Study design:} Over a one-year period, employees who sustained an upper extremity work-related injury were issued questionnaires regarding their injury, treatment, functional status and pain level. Participants were divided into three groups: group 1 consisted of hospital employees (N=14) who underwent worksite analysis, group 2 included university employees (N=15) who underwent worksite analysis whereas group~3 included university employees (N=14) who underwent no analysis.
{\it Results:} All groups were similar in demographics, functional status, and pain level. Satisfaction with the worksite analysis was similar for groups one and two.
{\it Conclusion:} A pattern of less absenteeism but greater modified duty days was associated with those individuals undergoing worksite analysis.
Work related conditions caused by overexertion or repeated trauma affect millions of American workers. These conditions can result in time off from work, decreased productivity, and high financial costs, not to mention impairment of the worker. According to the Occupational Safety and Health Act (OSHAct) of 1970 [26], employers are required to provide hazard free workplaces for their employees. Fortunately resources exist to help employers set up on-site ergonomic programs to reduce the hazards that contribute to cumulative trauma disorders (CTDs) or other injuries. Companies that have implemented comprehensive ergonomic programs have reported benefits, most significantly, decreased injuries, and cost savings. A model is described for industry on starting and managing a successful on-site ergonomic program.
The use of hand-held power tools can result in absorption of significant vibration energy by the worker's hand and arm, and is a causal factor in the development of various muskuloskeletal disorders (MSD's) such as carpal tunnel syndrome (CTS) and hand-arm vibration syndrome (HAYS). A novel brace incorporating vibration damping materials is proposed that could reduce this energy absorption, resulting in lower incidence of vibration-related occupational MSD's. The National Occupational Research Agenda (NORA) has identified this type of injury as a priority research area. The proposed brace will have utility in the top three NORA-sponsored areas for research tools and approaches: clinical assessment of exposure to environmental vibration; practical use as improved personal protective gear; and evaluating the effects of reduced vibration exposure on MSD incidence. Clinical test results for prototype braces on human volunteers are reported: splints with piezoelectric material showed a median improvement of 12% in vibration damping as compared to otherwise identical nonpiezoelectric splints (median allowable error of +/- 1.5%). The use of these splints to further study how the hand-arm system absorbs vibration energy is also discussed.
Training programmes in handling have been one of the most used means of preventing work-related backache. The effectiveness of these programmes has not yet been demonstrated however, since they have rarely been evaluated. The purpose of this study was precisely to assess one of these programmes in the hospital sector which specifically dealt with the handling of patients. A field study was conducted and handling methods used by 32 trained orderlies were characterized using an observational grid developed and validated specifically to describe patient handling operations. The extent to which these orderlies used the handling methods taught was determined, and the observed deviations from these methods were characterized and interpreted. The results show that the handling principles taught (working with a straight back using the legs) were not frequently used in the workplace. Furthermore, the use of training was closely related to the type of handling carried out. In handling operations in which the effort includes a horizontal component (mainly those carried out in bed) the training was hardly used, while in vertical handling operations the taught principles were more frequently used. These results suggest that actual training is not well adapted to the handling of patients, particularly to horizontal handling carried out in the bed. Two main deficiencies in the actual programmes are pointed out. First, it is shown that, for reasons of physical constraints, training could not always be applied; second, the rationale of the taught principles could also be questioned, particularly the emphasis given to the use of the legs.
The aim of this 12-month follow-up study was to evaluate the effect of the Swedish-type back school in chronic low back pain. 188 subjects completed the study (95 in the treatment group and 93 in the control group). The following were assessed: 1) subjective scores of pain and disability; 2) clinical measurement and evaluation including spinal mobility and strength measurement; 3) number and length of sick-leaves. At 12 months, subjective scores of pain and disability, and mobility of the lumbosacral section of the spine showed differences in the favour of the treatment group. There was no difference, however, in the number or the length of sick-leaves after the back school. It was concluded that patients with chronic or recurrent low back pain may get relief of subjective symptoms of low back pain from the back school. In addition to chronicity, there may be other factors affecting the outcome of treatment.
Repetitive trauma disorders of the upper extremity are a major cause of lost work in many hand-intensive industries. Reported risk factors include repetitive and forceful exertions, certain postures, mechanical stress, low temperatures, gloves, and vibration. Risk factors can be identified with job analysis procedures based on traditional work-methods analysis. Risk factors can be controlled through reallocation of work, balancing of tools, selection of alternative tool designs, work relocation, selection of suitable hand protection, and elimination of hand exposure to low temperatures and vibration. Drawing-board manikins are used with computer-aided design systems to estimate the best work location for a given task.
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Those who suffer peripheral vascular disease (PVD) frequently require lower-limb amputation. To prevent further difficulties with circulation, the socker and support system of the resulting artificial leg should be arranged so as to prevent impairment of blood flow. The mechanical stress factors tending to impede flow and cause stasis are investigated. An assessment is made of the relative importance of the two types of strees, normal and shear, in reducing the flow within a simulated vessel surrounded by a model flesh.
The paper presents a review of the literature on the prevention of low back injuries in industry and discusses the approach of designing the job to fit the worker by describing seven studies of lifting, lowering, pushing, pulling, carrying and walking. Among the variables investigated were the height, distance and frequency of the task; the size and weight of the object; the differences in worker sex, age, and physical physique; and the effects of heat stress.
This article provides a literature review of the ergonomic design of handheld tools. Too often the handle of the tool that connects the worker to his or her work becomes the cause of cumulative trauma within industry. With increasing costs of workers’ compensation, increasing work-related injuries, and increasing need for biomechanical alterations of work station designs, industries are developing new strategies. Safety and personnel managers are now more likely to ask for budgets that include work-station analysis to reduce the incidence of cumulative trauma. This article presents the correct ergonomic design of tools and work stations for work analyses.
An industrial accident/injury primary prevention program similar to traditional "back school" training, but based upon educational psychology principles such as "transfer appropriate processing" and the use of "critical tasks," was conducted for a group of 110 workcrs at a major grocery distribution center. Occupational therapy prevention principles of environmental modification, work simplification, and proper body mechanics were emphasized. Workers and supervisors were trained in very small groups (4-6 persons) at their actual work stations. Results of the program were positive, and the program has continued to expand into a comprchensive accidentlinjury prevention project within the company.
For the past 40 years it has been widely advocated that all lifting be carried out with a “squat lifting posture” (bend at the knees, back erect). The presumed basis for this has been to reduce the compressive force on the low back. Detailed biomechanical evaluations show that the more common “stooped lifting posture” (bend at the waist) may in fact be superior to the recommended squat method on this basis, even when the load can be placed close to the body. The compressive force on the lumbosacral disc is estimated to be equal or slightly lower for loads greater than 5 kg when the load is lifted using the stooped lift posture. This should not be viewed as sufficient evidence to reject conven- tional wisdom. The compressive force with the stooped-lift posture may in turn lead to a non-uniform distribution of pressure over the disc, thus enabling a smaller compressive force to produce rupture. Thus, there is no clear biomechanical rationale for deciding between the two postures. Using metabolic energy expenditure rate, on the other hand, as a basis for comparison suggests lifting with a stooped lift posture is preferred. It is further concluded that lifting heavy loads at slower paces is physically less taxing (in a metabolic sense) to the worker than lifting light loads at faster paces. The resulting trade-offs between the two criteria are discussed.
In order to ascertain which muscles and muscle groups are engaged in various standing work positions an electromyographic study was performed.About twenty muscles or muscle groups were examined. Both coaxial needle electrodes and surface electrodes were employed.The analysis of the muscle activity for different postures was based on action potentials recorded in a normal symmetric standing rest position. Among the different postures the rest position appears to require the least muscular effort for counterbalancing the effect of gravity on the various parts of the body. This state of equilibrium seems to be maintained by certain muscle groups, referred to hero a.s the “ prime postural muscles ”. Only a part of the potential power of the postural muscles is utilized in maintaining the standing symmetric rest position. Some persons engage other muscles besides the prime postural muscles, possibly because they stand in such a way that the load distribution is not optimal, or thoy havo weak prime postural muscles or because of poor muscular co-ordination as a consequence of “ non-physiologic” postural habits.When changing from the rest position to most of the other standing positions the load on the prime postural muscles is increased, and in many cases other muscle groups arc activated as well. The sacrospiualis appears to be particularly susceptible to change in the load distribution. The muscles of the lower leg, which control the foot articulation, are also very susceptible to changes in body posture. However, a change in the position of the- trunk need not result in an appreciable increase in the load on the muscles of the lower legs if the displacement of the centre of gravity of the trunk is compensated by a postural adjustment at the ankle, such that the point of intersection of tho line of gravity of the body and the supporting area will be the same as in the symmetric standing rest position.A change in posture of the hip- and knee-joints does not result in such a wide variation in activity of the muscles rogulating the position of these joints as a postural change in the foot articulation and the vertebrae.
The intervertebral disc pressure in the third lumbar disc, the intraabdominal pressure, and the myoelectric activity of several muscles of the back were recorded simultaneously in 4 healthy subjects. The studies comprised static pulling against a fixed resistance with the back either straight or flexed, dynamic lifting, and holding of a weight at various distances to the body. The distance between the weight and the body was found to influence the stress on the back much more than the method used to lift.
(C) Lippincott-Raven Publishers.
Though worker training is often chosen as a means to reduce the risk of low back pain if involved in lifting activities, the effect on a worker's lifting posture is rarely reported. This paper describes a video analysis method of recording lifting postures and the results of one evaluation of a training program specifically designed to modify lifting postures. It is concluded that a four-hour training program had beneficial but minor effects on the lifting techniques used by healthy workers in a warehouse when handling relatively light to moderate loads (i.e., 85% of loads lifted were below 30 pounds).
Magnitudes and correlates of stress were investigated among 248 office workplace VDT users and 85 nonuser counterparts using field survey and objective physical measurement techniques. Other than a tenuous indication of increased eyestrain and reduced psychological disturbances among users, the two groups were largely undifferentiated on job-attitudinal, affective, and somatic manifestations of stress. However, aspects of working conditions were judged less favorably by VDT users. Stress mechanisms were much the same for both groups, involving psychosocial as well as physical environmental job attributes. For VDT users, the chair and workstation configuration were particularly important predictors of musculo-skeletal disturbances, as were corrective eyewear use and ambient lighting for visuo-ocular disturbances.
Sumario: As companies search for answers to their ergonomic problems, they must realize that "quick fixes" won't work in the long run. Job rotation should be designed by an ergonomist to make sure that a worker is moved to a job that requires the use of different muscle groups
Sumario: A comprehensive training program based on body mechanics, job procedures, and exercise saved this company
The purpose of this investigation was to compare the prevalence of soft tissue disorders in the neck, arms and hands between packers doing repetitive work and shop assistants with variable tasks. One hundred and fifty-two female assembly-line packers in a food production factory and 133 female shop assistants were interviewed about their symptoms and given a clinical examination of the neck and upper extremities. The number of cases of tension neck, cervical syndrome, scalenus syndrome, and humeral epicondylitis did not differ significantly between the two groups. The prevalence of tenosynovitis and humeral tendinitis was significantly higher for the assembly-line packers. The packing work consisted of static muscle work by the arms, grasping and maximal extensions of the fingers, and lateral deviations of the wrists. The movements numbered up to 25,000/workday. A relationship between some work load factors and some disorders of the upper extremities is probable.
The prevention of low back injuries in industry has traditionally been attempted by (1) careful selection of workers, (2) good training in safe lifting, and (3) designing the job to fit the worker (ergonomics). One hundred ninety-one low back injuries were analyzed to determine the effectiveness of each preventive approach. The results indicate that the common selection techniques, as they are being used today, are not an effective control for low back injuries. Similarly, training on safe lifting procedures, as it is being administered today, is not an effective control for low back injuries. It was determined that a worker is three times more susceptible to low back injury if exposed to excessive manual handling tasks. The ergonomic redesign of these tasks to reduce the manual handling exposure represents a partial control for low back injuries.
The myoelectric activity of some of the posterior muscles of the back was studied quantitatively using signal amplitude estimation and power spectrum analysis. Surface electrodes were placed on both sides of the trunk at T4, T8, L1, L3, and L5 levels. Four different angles of forward flexion were studied during external loading of the spine with 200 N. At 30 degrees of forward flexion studies were made when the load was increased from 0 to 300 N. Asymmetric loading was studied with the trunk erect, in lateral flexion, and in rotation.
The myoelectric activity increased when the angle of flexion increased and when the external load was increased at a fixed angle of flexion. During asymmetric loading, comparatively higher activity was found on the contralateral side in the lumbar region and on the ipsilateral side in the thoracic region.
The magnitude of the power spectrum changes correlated well with the amplitude of the myoelectric signal. Spectral changes increased when the signal amplitude increased, indicating localized muscle fatigue.
A survey of those features of hand tools relevant to the physical interaction between the implement and the human operator. Concepts basics to the optimization of forces are mentioned, followed by a description of some of the more common physiological problems and musculoskeletal complaints associated with improper hand tool and design and usage. An account of the distribution of contact pressures and possible consequences, if these are excessive, is followed by a description of the role of working gloves as related to ergonomic problems and their possible relationships to occupational diseases of the hand and wrist. Some aspects of anatomy and anthropometry pertinent to the optimization of posture, motion patterns and tool size precede a list of desirable features for power tools. A glossary is included as an aid to the reader. The concepts and situations described are applicable to the design and use of the vast majority of hand tools.
Populations untrained in postural principles and retaining the ability to squat and sit cross legged for prolonged periods suffer litte if any back strain and demonstrate a greatly diminished incidence of disc degeneration. Western populations have lumbar discogenic problems and a high incidence of lumbar disc degeneration. Pathogenesis of disc degeneration incriminates Western posture and treatment by postural correction eases pain. Therefore, as a prophylactic measure, we could stop promoting Western posture and use postural correction in treatment.
The double crush hypothesis suggests that serial constraints to axoplasmic flow, each of which is insufficient to cause changes in function by itself, can be additive in causing ultimate dysfunction of the nerve. Careful clinical examination will be required to localize the significant levels of nerve compression. Frequently, patients will be asymptomatic in the nonprovoked position. A comparison of neurological testing "at rest" and then subsequent to provocation of the patient's symptoms may be the only mechanism by which the surgeon will be able to quantity an abnormality that corresponds to the patient's symptoms. Surgical intervention, especially when the etiologic factor is work-related, is always postponed until maximum job modification has been carried out. Surgical management of these patients without a significant change in the patient's work habits that provoked the compression neuropathies in the first instance will frequently be associated with a recurrence of symptoms when the work is resumed.
Ulnar nerve compression about the elbow is common. If diagnosed and treated early, satisfactory results can be expected. Severe chronic nerve compression may lead to permanent nerve damage. The diagnosis can be made by careful history, physical examination, knowledge of the nerve anatomy, and sometimes electrodiagnosis. Cubital tunnel syndrome must be differentiated from TOS and ulnar tunnel syndrome. Double-crush syndrome should be ruled out. Nonoperative treatment must be attempted first, whereas surgical treatment is indicated in severe and chronic cases. Satisfactory results can be achieved after surgery if nerve damage is absent and careful attention to technical details and gentle handling of the nerve are exercised.
Compression neuropathies of the median nerve in the proximal forearm are unusual lesions. Many patients have vague symptoms for many months or even years prior to confirming the diagnosis of either pronator syndrome or anterior interosseous syndrome of the forearm. Serial examinations clinically and electrodiagnostically may be necessary at intervals of 6 to 8 weeks as required for the evaluation of the patient’s symptoms. As with other compression neuropathies, the diagnosis is solely dependent on the diagnosis of neuropathy of the median nerve using whatever parameter satisfies the surgeon’s diagnostic criteria and then having made that diagnosis, localizing the site of that neuropathy by physical examination or electrodiagnosis with the support of radiographic techniques as appropriate.
Surgical exploration of proximal median nerve compression is normally followed by prompt and predictable recovery from the median neuropathy and clinical symptoms between 8 and 12 weeks after surgical exploration. Prolonged symptom complexes after surgical exploration of the proximal median nerve are, in my experience, due to either (1) extremely severe median nerve injury secondary to pronator syndrome with prolonged recovery and distal nerve axomnetic recovery into the hand, or (2) sensory nerve dysesthesis of the small sensory nerves on the proximal volar surface of the forearm. The symptoms of either of these postoperative findings normally improve with time.
The physician responsible for the evaluation and treatment of athletes must include nerve compression injury in the differential diagnosis of upper extremity pain and dysfunction. Careful history and physical examination, along with selective objective testing, should be diagnostic. Treatment and prevention methods implemented under the supervision of knowledgeable trainers and coaches may allow for complete resolution of symptoms and, more importantly, prevent recurrence. Adolescents and novice athletes in many sports may be at the highest risk for this type of overuse injury.
Cumulative trauma disorders are frequently responsible for the development of occupational neuropathy. Predisposing factors in the workplace are identified, and ergonomic principles to minimize these risks are presented.
Fifty-eight subjects, 23 female and 35 male, 19-62 years of age employed by four local industries, participated in one of three different Back Injury Prevention Programmes offered by a community hospital. Group A, 31 males, received two 1.5 hr classes of informational and exercise instruction plus mandatory 10-min daily exercise participation. Group B received three 1-hr mandatory classes of informational and exercise instruction with no follow-up daily exercise, and Group C received 1 hr of information and exercise demonstration only. Differences in body mechanic performance between the three groups were examined using Body Mechanic Questionnaire (BMQ) scores. The BMQ consists of 11 Likert-type questions developed by the researcher which were administered pre-, 1-week post-, and 3-months post-class instruction. At final post-testing, Group A showed a 12.9% improvement over pre-test scores; Group B, a 5.1% increase; and Group C, a 13.3% increase. These findings are discussed in terms of mandatory, continued reinforcement and Pender's Health Promotion Model.
In a prospective trial, 222 adults with low-back pain of at least 2 weeks' duration in a Health Maintenance Organization (HMO) were randomly assigned to usual care (UC), a 4-hour back school psychoeducational session (LBS), or the same back school plus a 1-year "compliance package" program designed to encourage appropriate self-management for back pain (CP). Sixty-four percent of LBS and CP subjects attended their back school sessions. Follow-up measurement of pain level (using the Visual Analogue Scale), functional status (using the Sickness Impact Profile), and various other indicators of health status showed no measurable effect of either treatment condition (LBS or CP) compared with UC at 3, 6, 12, and 18 months after entry into the study. Initial disability resolved by 3 months in most patients, and a minority of subjects (10-15%) showed residual or recurrent functional impairment 1 year after entry. Health care utilization tended to be slightly higher after intervention in the CP group. With or without follow-up encouragement, back school instructions given in a single 4-hour session had no measurable impact on the comfort or functional status of the majority of patients with new onset back pain in this HMO.
Ninety-two chronic low back pain patients were randomly allocated to two groups to evaluate the effectiveness of a back school compared with an exercise-only regimen according to specified outcome variables. The data from 78 patients with 7 years mean duration of symptoms was analyzed. Three assessments were made: before treatment and 6 and 16 weeks after treatment. Changes in patients' levels of pain, functional disability, and other related variables were compared in the two groups. Almost all variables showed an improvement at 6 weeks. At 16 weeks, functional disability and pain levels showed a significant difference. Back school patients continued to make an improvement. This method of managing low back pain makes maximal use of limited resources and appears to be effective, especially in the longer term.
Two phases of a back injury prevention program were studied using 2035 accident reports filed between 1979 and 1984. Phase 1, Personnel Program, was designed to decrease the duration of wage-loss claims by increasing the effectiveness of the existing procedures used to process these claims. This program significantly lowered the proportion of high-hour claims (P less than .05) and significantly reversed a trend of increasing accident rates (P less than .05). Phase 2, Back Program, was designed to lower the incidence of back injuries through a feedback-oriented educational program. The Back Program itself could not demonstrate a significant reduction in back injuries primarily due to the powerful and confounding effect of the Personnel Program. The combination of the Personnel Program and the Back Program significantly lowered back injuries for nurses when compared with a similar group of injuries that occurred at geriatric hospitals (P less than .001). The large effect of the Personnel Program and the small effect of the Back Program have design implications for any injury prevention program.
It appears possible to control back pain by reducing the probability of the initial episode, reducing the length of the disability, and reducing the change of recurrence. Progress toward these goals may be possible with a combination of job design, job placement and education/training.
Because back pain is a widespread and costly condition that tends to recur, treatment must focus on both the amelioration of acute symptoms and prevention over the long term. This paper reports a longitudinal evaluation of a program from a community hospital that emphasizes both these aspects. One hundred twenty patients routinely admitted to this program were randomly assigned to treatment and control groups. These groups were assessed for differences in demonstrated physical strength, mobility, body mechanics, and self-care knowledge, and in levels of self-reported exercise, anxiety, and pain. There were significant immediate gains on physical measures of fitness and in observed body mechanics; patients also reported significant gains in physical capabilities at home and in leisure activities. Self-care knowledge also improved. When assessed one year later, original gains in physical strength and mobility were being maintained, and self-reported physical capabilities also remained high. Although demonstrated knowledge of correct body mechanics declined over this period, it was still significantly greater than before the program. In light of these results, we believe that outpatient programs like the one reported here merit careful consideration in an era of concern about rising costs for primary health care.
A survey of supermarket checkers was undertaken early in 1986 to assess the prevalence of symptoms of carpal tunnel syndrome (CTS). Following three mailings, 83% of the 1,345 checkers had responded. The analysis, which was restricted to female workers aged 18 to 49 years, showed an overall prevalence of self-reported CTS symptoms of 62.5%. Prevalence rates were related to use of laser scanners, age, years worked as a checker, and average number of hours worked per week. The findings were similar when more restrictive criteria of CTS symptoms were used. Use of estrogens was not positively related to reported CTS symptoms.
This article illustrates the use of a simple questionnaire in identifying those sections of a work force at risk for musculoskeletal disorders and chronic discomfort of the upper extremities. Two research studies are described. The first, conducted in a chicken-processing factory, illustrates the use of self-administered questionnaires in the assessment of the musculoskeletal health of the work force and in the identification of groups of workers who may be at increased risk and for whom ergonomic reappraisal of the tasks performed may be beneficial. A second study of retail trade staff suggests that chronic musculoskeletal discomfort is widespread. The article further considers the importance of such data for those persons concerned with the allocation of health care. The need to consider the broader spectrum of musculoskeletal health from discomfort to clinical disorder is stressed.
Over the past 10 years, Ethicon, Inc., has developed a successful program for the management of cumulative trauma disorders. The program is based on a multidisciplinary approach created through the existence of an ergonomics task force. Various functions of the task force and examples of its operations are described.
Incorrect hand tool designs can cause a variety of cumulative trauma disorders. Design elements of size, shape, texture, purpose, ease of operation, shock absorption, and weight must be properly applied in the design process to fulfill the physical safety needs of consumers and working people and to prevent the appearance of pathologic changes in the tissues of the hand and wrist.
Skin forms a link through which the forces required to hold and manipulate objects are transmitted from the musculoskeletal system to the objects; while these forces are necessary for most work, excessive forces can be injurious. This paper discusses some of the mechanical properties of skin and discusses how they are important in manual work. Recommendations for the design of hand-held objects and for future research are given.
The deep layers of the transversospinal back muscles were studied in 25 healthy human subjects. Bipolar fine wire electrodes were inserted bilaterally at the level of the sixth thoracic and the third lumbar spinous processes. Activity was registered simultaneously in sitting and standing, and during movements while in these positions. It was shown that the same muscle group displayed different patterns of activity in the thoracic compared to the lumbar level. Variations in the pattern of activity during forward flexion, extension and axial rotation suggest that the transversospinal muscles adjust the motion between individual vertebrae. The experimental evidence confirms the anatomical hypothesis that the multifidi are stabilizers rather than prime movers of the whole vertebral column.
An experiment was designed using muscle electromyography to determine if an optimum cylindrical handle size exists. The experiment had two phases. One phase was concerned with an experimental task of gripping a cylindrical handle and performing a simple task routine to evaluate the optimum handle size. The other phase was concerned with a fatigue test utilizing the same cylindrical handles. The experimental variables wore: hand size, weight resistance, and cylindrical handle diameter.Findings indicate that generally the 20 in. diameter handle showed lowest EMG activity. The 1-5 in. diameter handle was found to be the optimum handle size based on the ratio between force applied and the EMG activity measured. The 1.5 in. diameter handle was found to provide the maximum number of completed task cycles before the onset of fatigue.
— The coefficient of friction has been determined for skin and various materials. It has been established that the behaviour of skin is not portrayed by the simple laws of friction, but by a more complex relationship of the type F =μWn. This is probably because skin is subject to viscoelastic rather than purely plastic deformation. Friction may be altered by the type of material in contact with skin and is further influenced by surface lubrication. Dry talcum powder reduces friction slightly for certain materials against skin, but increases friction when it becomes wetted.