Personal and occupational factors contributing to biomechanical risk of the distal upper limb among dairy workers in the Lombardy region of Italy.

Biomechanical overload in the wrist flexor and extensor muscles, together with awkward hand positions during work activities, can result in occupational wrist and hand disorders. Dairy workers, specifically those that work in the milking parlor, are exposed to highly repetitive and forceful exertions of the upper limb throughout their work shift. There are very few studies that have investigated the determinants that contribute to the risk of distal upper limb musculoskeletal disorders among dairy workers. The purpose of the present study was to identify the variables affecting the biomechanical overload of the distal upper limb among milking parlor workers, define risk profiles, and propose possible interventions to reduce the high physical loads to the distal upper limb during milking activities. Forty male workers from the three most common milking parlor systems in Lombardy Italy were recruited to participate in this study. Multiple correspondence analysis of personal characteristics and occupational risk factors, followed by cluster analysis, led to the identification of three distinct groups of workers. Low, medium and high risk profiles were assigned to each group based on the risk assessments performed using the Strain Index and electromyography of the distal upper limb. The main risk determinants were workstation characteristics, work organization and milking routine. A well-organized milking routine, milking cluster weight below 2.4 kg or the use of supporting arms for the milking cluster may reduce the risk of biomechanical overload.

Assessing the effects of biomechanical overload on dairy parlor workers' wrist: Definition of a study approach and preliminary results.

BACKGROUND: Dairy milking is a demanding work task that has been associated with hand and wrist musculoskeletal disorders. Clinical approaches to identify the early effects of musculoskeletal disorders among dairy parlor workers' wrist have not been well defined. OBJECTIVES: The purpose of this pilot study was to develop a study protocol that would assist in the identification and quantification of hand and wrist disorders among dairy workers that perform tasks in the dairy parlor. Additionally, such a study protocol was needed to perform relatively rapid assessments of the wrist/hand on large samples of dairy workers. METHODS: Fourteen dairy parlor workers were assessed for i) upper limb symptoms and work history through questionnaire, ii) a physical examination of the upper limb and in particular wrists and iii) wrist ultrasonography. An additional 21 unexposed paired participants (the control group) also participated in the data collection. RESULTS: The study results identified two ultrasound acoustic windows characterized by the highest predictive value for alteration of the wrist's structure. Study results indicated an impairment of the distal median nerve in structure and mobility and impairment of the distal tendon of the muscle extensor carpi ulnaris that included dislocation and frank damage. CONCLUSIONS: This study identified at least two acoustic windows that should be assessed with ultrasound studies on larger groups and in prospective periodical health surveillance of dairy workers. The study confirmed the wrist was at risk for biomechanical stress among workers conducting milking tasks in the dairy parlors.

Effect of concrete block weight and wall height on electromyographic activity and heart rate of masons.

Work-related musculoskeletal disorders (MSDs) are common among construction workers, such as masons. Few interventions are available to reduce masons' exposure to heavy lifting, a risk factor for MSDs. The purpose of this study was to determine whether one such intervention, the use of light-weight concrete blocks (LWBs), reduces physiological loads compared to standard-weight blocks (SWBs). Using a repeated measures design, 21 masons each constructed two 32-block walls, seven courses (rows) high, entirely of either SWBs or LWBs. Surface electromyography (EMG), from arm and back muscles, and heart rate was sampled. For certain muscles, EMG amplitudes were slightly lower when masons were laying LWBs compared to SWBs. Upper back and forearm extensor EMG amplitudes were greater for the higher wall courses for both block weights. There were no significant differences in heart rate between the two blocks. Interventions that address block weight and course height may be effective for masons.

The effect of overhead drilling position on shoulder moment and electromyography.

The effect of overhead drilling tasks on electromyographic (EMG) activity and shoulder joint moment was examined in this study. Twenty subjects simulated an overhead drilling task using a close, middle and far reach position while standing on either a lower or a higher step of a stepladder. Root mean square amplitude (AMP) of EMG activity from the dominant side anterior deltoid, biceps brachii and triceps brachii muscles was used to determine muscular load. Digital video was used to determine shoulder joint moment using 2-dimensional static link segment modelling in the sagittal plane. The results demonstrated that, compared to the far reach position, using the close reach position significantly decreased anterior deltoid AMP and biceps brachii AMP and moment, but increased triceps brachii AMP. Compared to the lower step, using the higher step significantly decreased anterior deltoid AMP and triceps AMP and moment, while increasing biceps AMP in the close position. There was no significant change noted in EMG median frequency indicating that fatigue was minimized. Moment increased monotonically with AMP. The findings indicated that workers performing overhead tasks should work close to their body in order to minimize shoulder forces. The implications of this recommendation are discussed.

Musculoskeletal disorders among construction apprentices in Hungary.

The purpose of this study was to determine the prevalence of occupationally related musculoskeletal disorder (MSD) symptoms and carpal tunnel syndrome (CTS) among construction apprentices in Hungary. Symptoms of occupational MSDs and the job factors contributing to the symptoms were determined through an administered symptom and job factors survey. The prevalence of CTS was based on a case definition that included hand symptoms and nerve conduction studies of the median nerve across the carpal tunnel. The participation rate was 96% among the 201 eligible construction apprentices. More than 50% of the apprentices reported occupationally related musculoskeletal symptoms in the previous 12 months. Job tasks that required awkward postures and working in a static position were the two factors that contributed most to MSD symptoms. No cases of CTS were found in this sample of apprentices. Although disorders of the musculoskeletal system are more prevalent among experienced construction workers, this study indicated that symptoms of MSDs are present among young construction workers. Assessing the magnitude and nature of occupational related MSDs is the first step in promoting a healthier, safer, and more efficient workforce.

The use of participatory action research and ergonomics in the prevention of work-related musculoskeletal disorders in the newspaper industry.

The newspaper industry is one of many in which employees are reported to be at risk for work-related musculoskeletal disorders of the upper extremities and low back. The purpose of this 18-month demonstration project was to assess the usefulness of a participatory ergonomics process as a strategy to reduce the risk factors associated with musculoskeletal disorders at a metropolitan newspaper company. The company involved had 455 employees and a daily circulation of 75,200. Employees from both office and production areas participated. The participatory action research approach utilized required investigators to work collaboratively with the study population. Using a five-step continuous improvement process, the ergonomics committee identified and evaluated jobs having ergonomic risk factors. This was followed by the development, implementation, and evaluations of interventions aimed at reducing risk factor exposure. The committee's productivity and participant feedback were used as measures of the committee's effectiveness. During the project period, interventions were implemented in 11 of 12 targeted departments. Participant ratings of effectiveness for different aspects of the ergonomics process were generally favorable. The mean and median cost for ergonomic interventions were $376 and $25, respectively. This project demonstrated that participatory action research could be used to develop and implement ergonomic solutions that reduce the risk factors associated with work-related musculoskeletal disorders.

Electromyographic effects of ergonomic modifications in selected meatpacking tasks.

This project evaluated the feasibility of a new method of collection of electromyographic (EMG) data during working conditions in industry, and quantified the effects of specific job modifications on the EMG activity of selected upper extremity muscle groups. Average root mean square (RMS) surface EMG activity, calibrated to force equivalent units, was collected on 20 workers from three pork processing tasks before and after ergonomic modifications to their tasks. Significant reductions in muscle effort were detected in the biceps and/or wrist and finger flexors after modification for two of the three tasks. This EMG measurement technique can be used to objectively validate reduced muscle effort with ergonomic modifications.

Sensory nerve recovery following median nerve provocation in carpal tunnel syndrome.

The purpose of this study was to evaluate the recovery of median nerve sensory nerve action potentials (SNAP) following median nerve provocation in hands with carpal tunnel syndrome (CTS). Repeated nerve conduction measurements were performed before and after wrist flexion combined with resisted finger flexion in 35 hands with a clinical diagnosis of CTS and in 25 asymptomatic control hands. Orthodromic sensory median nerve potentials were recorded over an 8 cm segment between the palm and wrist. Hands with CTS had significant reductions in nerve potential amplitude and latency following median nerve provocation. Hands with mild to moderate CTS, had the greatest reductions in nerve potential amplitude and the longest amplitude recovery times following median nerve provocation. Determination of changes in amplitude and amplitude recovery time of the median nerve SNAP following median nerve provocation has the potential to improve the accuracy of the electrophysiological diagnosis of CTS.

Prevalence of abnormal median nerve conduction in applicants for industrial jobs.

There has been much debate regarding the work relatedness of carpal tunnel syndrome (CTS) and whether workers diagnosed with CTS had pre-existing disease at the time they were hired. To elucidate the latter issue, we examined the prevalence of abnormal median nerve conduction within the carpal tunnel in applicants for industrial jobs. Nerve conduction studies (NCS) were performed on both hands of 1,021 applicants following a conditional offer of employment. Each applicant completed a self-administered symptom survey specific to the upper extremity. Applicants had worked previously for an average of 4.4 (range 0-33) years and had a mean age of 30.1 (S.D. 8.9) years. Nerve conduction studies were performed in a private medical clinic. Sensory palmar latencies were determined over an 8 cm segment for the median and ulnar nerves. The difference between the median and ulnar sensory latencies was the primary electrophysiologic measurement used to determine median neuropathy. Using a very conservative criterion for abnormal median nerve conduction, 17.5% of the applicants were classified with neuropathy in at least one hand. Despite the relatively high prevalence of median neuropathy, relatively few (10%) with positive NCS acknowledged symptoms associated with CTS. Males had a higher percentage of median neuropathy than did females. We conclude that a large percentage of industrial workers have objective evidence of abnormal median nerve conduction within the carpal tunnel when hired. The high prevalence of abnormal median nerve conduction without corresponding symptoms may suggest a subclinical entity associated with CTS.

Work-related musculoskeletal disorders among physical therapists.

BACKGROUND AND PURPOSE: Increasing evidence suggests that musculoskeletal disorders are common in workers in the United States health care industry. Physical therapists, who commonly treat patients with these disorders, are also at risk for work-related musculoskeletal disorders (WMD) in the upper limbs and low back. The purpose of this study was to determine the prevalence of WMD during a 12-month period and the job factors that may be associated with these disorders in physical therapists. SUBJECTS: A four-page questionnaire was mailed to physical therapists (N = 1,160) who attended The University of Iowa between 1943 and 1993. Nine hundred twenty-eight questionnaires were returned (80% response rate) from physical therapists in 46 states. METHODS: Based on a literature review and pilot study of physical therapists, a survey instrument was constructed consisting of a symptom survey, a job-factor survey, and various demographic information. RESULTS: The highest prevalences of WMD among physical therapists were in the following anatomical areas: low back (45%), wrist/hand (29.6%), upper back (28.7%), and neck (24.7%). The job factor rated most likely to contribute to job-related musculoskeletal disorders was "lifting or transferring dependent patients." The prevalence of WMD in physical therapists also was affected by work setting, practice specialty, age of patient, and gender of therapist. CONCLUSION AND DISCUSSION: Specific strategies should be developed to reduce WMD in the practice of physical therapy.

Effectiveness of a physical therapy regimen in the treatment of tension-type headache.

Twenty patients with diagnosis of muscle contraction headache were treated for pain relief in a physical therapy clinic once a week for six visits. The previous 3-week period of no treatment served as a control period during which patients recorded by diary their headache frequency, duration, and intensity using a numeric pain scale. Activity level, as measured by the Sickness Impact Profile, and verbal reports of headache frequency, duration, and intensity were recorded at four points during a 1-year period. Measurements were recorded at precontrol, pretreatment, posttreatment, and 12-month follow-up. Treatment included education for posture at home and work place, isotonic home exercise, massage, and stretching to the cervical spine muscles. Results indicated frequency of headaches and Sickness Impact Profile scores were significantly improved (P < 0.001) over the course of treatment. These benefits were maintained after 12 months.

Work-related musculoskeletal symptoms among construction workers in the pipe trades.

Workers in the construction trades experience high rates of injuries and illnesses, including work-related musculoskeletal disorders. As the basis for formulating and implementing ergonomic changes to reduce musculoskeletal disorders among workers in the pipe trades, a cross-sectional survey was conducted. The survey instrument assessed the prevalence of work-related musculoskeletal symptoms and identified job factors that may contribute to those symptoms. A two-page questionnaire was mailed out to members of three plumber and pipe/steamfitter unions. Results from 526 (40% response rate) apprentices and journeymen indicated that the highest work-related symptoms and reported lost work time due to those symptoms, were in the back, neck, and knees. Awkward postures and working in the same position for long periods were identified as the leading causes of work-related musculoskeletal symptoms. These results can be used to formulate appropriate intervention strategies for the reduction of musculoskeletal symptoms for construction workers in the pipe trades.

Vibration sensibility testing in the workplace. Day-to-day reliability.

Loss of vibration sensibility has been suggested as an early indicator of peripheral compression neuropathy, including carpal tunnel syndrome. Although vibration sensibility has been used frequently to evaluate carpal tunnel syndrome, the day-to-day reliability of vibration measurements in an industrial population measured at the workplace has not been assessed. Vibration sensibility testing was performed at the university ergonomics laboratory on 50 volunteers (100 hands) and at a newspaper company on 50 workers (100 hands). Vibration perception and disappearance thresholds were measured on two occasions separated by 3 to 5 days. Student's t tests indicated no significant differences between the first and second tests or between the two groups. Pearson product-moment correlations for test-retest reliability were lower in the industry group but were relatively high despite the less than optimal testing conditions. Our findings suggest that vibration sensibility measurements are reliable from day to day not only in the laboratory but also in the workplace.

Active surveillance for the control of cumulative trauma disorders: a working model in the newspaper industry.

Health and risk factor surveillance is a critical aspect of an effective ergonomics process. Physical therapists are becoming increasingly involved in many components of the ergonomics process, including health and risk factor surveillance. The purpose of this study was to develop and implement a multistaged active surveillance program for the management and control of cumulative trauma disorders. The surveillance program was established at three newspaper companies consisting of 1,150 employees. This study focused on the first three stages of the multistage surveillance model, which incorporates the use of symptom and job factor questionnaires, specific anatomical surveys, and clinical detection tests. The results of the study indicated that 1) musculoskeletal symptoms in the back, neck, and hands accounted for the majority of reported missed work among the newspaper workers; 2) production workers had a higher prevalence of musculoskeletal symptoms than office workers; and 3) the prevalence of probable carpal tunnel syndrome among the newspaper workers was 1.5%.

Reliability of distal sensory latency measures of the median nerve using an electroneurometer.

Measurements of distal sensory latency are often used to support the clinical diagnosis of carpal tunnel syndrome (CTS). Currently, there is little research that documents the reliability of measuring distal sensory latency in adult populations. The purpose of this study was to determine intraexaminer and interexaminer reliability of antidromic distal sensory latency of the median nerve in normal subjects (n=37). Using a two factor design, three examiners obtained a total of six distal sensory latency measures using a supramaximal stimulus from each subject. Analysis consisted of intraclass correlation coefficients (ICC) for intraexaminer and interexaminer reliability, which were 0.89 and 0.83, respectively. The results indicate that this method of measuring median nerve sensory latency has a high degree of reliability and agreement within and between examiners.

Comparison of a digital electroneurometer and standard nerve conduction studies for the measurement of median nerve sensory latency.

The purpose of this study was to determine the validity of measuring median nerve distal sensory latency with a portable digital electroneurometer. The results from the digital electroneurometer were compared to standard nerve conduction studies in 51 subjects (40 asymptomatic hands and 12 hands with probable carpal tunnel syndrome). There was a high correlation (r=0.92) between the latencies obtained from the electroneurometer and the onset latencies measured by standard nerve conduction studies. The mean difference between distal sensory latencies for matched pairs of latency measurements was 0.09 (+/-0.21) ms. The use of the digital electroneurometer for obtaining distal sensory latencies proved to be objective and valid. The electroneurometer would be useful in a variety of occupational and clinical settings for screening of peripheral neuropathy where standard nerve conduction equipment may be unavailable or impractical.

Kinematic analysis of lower-limb movement during ergometer pedaling in hemiplegic and nonhemiplegic subjects.

The purpose of this descriptive study was to examine bicycle pedaling as a model for studying motor control dysfunction in persons with hemiplegia. Results of a kinematic analysis of the involved lower extremity of 10 hemiplegic patients were compared with the lower-extremity kinematic data of 10 "normal" (nonhemiplegic) subjects. Subjects pedaled at a constant work load at two pedaling rates. Hip, knee, and ankle angular-displacement variables were studied. Statistical comparisons for variables at the hip and knee were not significantly different between groups or between pedaling speeds. Ankle dorsiflexion and total ankle excursion were significantly different across pedaling speeds, but not between groups. Phase-plane analyses of angular-displacement and angular-velocity variables revealed that the most striking difference between the hemiplegic and the normal subjects was the control of ankle displacement and velocity of the lower extremity during pedaling.

Reliability of a digital electroneurometer for the determination of motor latency of the median nerve.

Measurement of distal motor latencies of the median nerve are often part of electrodiagnostic studies used to verify a diagnosis of peripheral neuropathy. Since electrodiagnostic studies are time consuming, expensive, and impractical for large-scale screening of at-risk individuals, a portable digital electroneurometer was developed for measuring motor latencies as a screening tool for early detection of nerve compression syndromes, including carpal tunnel syndrome. The purpose of this study was to determine the intertester and intratester reliability of a digital electroneurometer in subjects with (n=12) and without (n=20) clinical signs of carpal tunnel syndrome. This study addressed only the reliability and not the validity of this device. Using a repeated measures design, three evaluators performed two distal motor latency tests on the median nerve of each of the subjects. Pearson product-moment correlations for intratester reliability ranged from 0.94 to 0.99, and the intraclass correlation coefficient for intertester reliability was 0.96. Two examiners obtained statistically larger latency values on the second test, although these differences are judged to be clinically insignificant. Use of an electroneurometer may expand motor latency testing to a wider variety of settings.

A comparison of isometric strength and dynamic lifting capacity in men with work-related low back injuries.

Job classification, return to work status, and job placement are determined by the results of lifting capacity tests. Lifting capacity is often assessed by maximum static or dynamic physical exertions. The purpose of this study was to compare maximum isometric lifting strength with maximum dynamic lifting capacity in subjects with work-related low back injury. Twenty-seven men performed five dynamic lifting tasks and two isometric strength tests. The mean Pearson product-moment correlation between maximum isometric lifting strength measurements and maximum dynamic lifting capacity measurements was .51 with a range of .30-.73. The results indicate low to moderate associations between isometric strength measurements and lifting capacity suggesting that estimates of functional lifting capacity should not be based on static measurements alone. Dynamic lift tests are often a better simulation of the task being assessed and may be more appropriate for a back-injured population.