Biomedical subjects

Patrick G Dempsey

Publications and source records attributed to Patrick G Dempsey.

18 recordsLinked to original sources

PubMed2006

Cross-sectional investigation of task demands and musculoskeletal discomfort among restaurant wait staff.

A cross-sectional study of task demands and musculoskeletal discomfort among a sample of 100 wait staff in ten casual dining restaurants was conducted. In addition to answering a questionnaire about musculoskeletal discomfort and symptoms experienced in the past 12 months and attributed to work, subjects were asked about various aspects of their jobs, such as shift length, number of shifts per week and safety training. The managers of the restaurants were also interviewed to gather basic information on factors such as work hours, alternative duty availability and safety practices. When asked to rank the three most important causes of injuries, the responses of both managers and wait staff were congruent with Bureau of Labor Statistics (USA) data for 1999 on the nature of injuries and attributed exposures, with slips and falls, musculoskeletal disorders and acute injuries (e.g. burns, cuts) highlighted. Of the 100 subjects, 42% reported experiencing musculoskeletal symptoms in the past year, with the lower back area (18%) and shoulder (11%) with the most frequent symptoms reported in the responses. Although many of the materials handling tasks were not excessive, the heavier tray lifts and carries are a cause for concern. There are also slip and fall issues that influence the risks of these tasks. Future research needs, including addressing the mismatch between more common materials handling assessment tools and the nature of food serving tasks, are discussed.

Accidental Falls↗

PubMed2005

Handle displacement and operator responses to pneumatic nutrunner torque buildup.

The objective of this study is to investigate the workstation and tool effects on the responses of the powered hand tool operator reacting against the impulsive reaction forces that may be associated with upper extremity musculoskeletal disorders. The study demonstrated a means of direct measurement of force at the interface between the tool and the operator. Fifteen experienced male operators performed three independent work configurations: pistol grip and right angle tools used on the horizontal surface and pistol grip tools used on the vertical surface, in the laboratory. A full factorial experiment consisting of 36 conditions was designed to examine the effects of working height, distance, tool, and fastener joint hardness on handle displacement and grip forces. The results indicate that operator responses were affected by different factors depending on the work configuration. When pistol grip tools were used on the vertical surface, the mean handle displacement decreased from 9.9 degrees to 7.3 degrees as the working height increased from 30 cm below shoulder to 30 cm above shoulder. When right angle tools were used, the greatest handle displacement (51.1mm) and grip force (84.7% MVC) during torque reactions were measured at 30 cm below elbow and 40% forward reach away from the operator. This study provides quantitative information that can be used for workstation design and tool selection to reduce the torque reaction experienced by powered nutrunner operators.

Adult↗

PubMed2005

On the evolution of task-based analysis of manual materials handling, and its applicability in contemporary ergonomics.

The industrial revolution significantly changed the way work was organized and analyzed by the introduction and widespread implementation of the division of labor philosophy. This philosophy has continued to dominate work design, and has evolved beyond the factory to include many facets of service industries, and even professional occupations. The analysis of manual work, particularly materials handling tasks, remains an active domain of ergonomics research and practice. Many of the task-analytic tools used for workplace analysis are rooted in the philosophy of dividing work into elements, analyzing the individual elements, and synthesizing the results into conclusions about the entire job, including the risk of contracting musculoskeletal disorders (MSDs). The authors discuss the notion that the nature of modern work, which is characterized by multiple tasks in a complex time pattern, and the complex nature of MSDs, which are influenced by biomechanical as well as psychological, political, and economic factors, may limit the effectiveness of classical task analytic techniques in preventing MSDs.

Ergonomics↗

PubMed2005

A survey of tools and methods used by certified professional ergonomists.

A survey of Certified Professional Ergonomists (CPEs) was conducted to gather information on the types of basic tools, direct and observational measurement techniques, and software used by practitioners. The motivation for the survey was to better understand what types of tools and methods practitioners use, their opinions of these tools, and to potentially gain an understanding of the constraints or preferences that influence this selection. Reasons for using or not using a selection of tools were also surveyed. Of 578 surveys that were delivered to CPEs and Associate Ergonomics Professionals, 308 were returned for a response rate of 53%. The respondents tended to be biased towards physical ergonomics, as the survey primarily focused on this area of ergonomics. A high percentage of respondents reported using tape measures, video cameras, stopwatches and digital cameras. The most commonly used observational methods were those involving manual materials handling, whereas the most commonly used direct measurement tools were pinch and grip dynamometers and push/pull gauges. The frequency and type of checklists, software, and anthropometric data used are summarized.

Certification↗

PubMed2005

A technique for field measurement of knife sharpness.

Knife sharpness can affect the productivity of meatpacking operations as well as the forces to which meat cutters are exposed. This report describes the development and evaluation of a "sharpness tester" designed to meet the criteria that the system be portable for field use at meatpacking plants, requires no special skills to operate, provides a non-destructive test of the entire blade edge, and incorporates a test motion that is representative of meat cutting. The system was bench tested for sensitivity to incremental changes in blade sharpness; suitability of the test material as a surrogate for red meat; and ability to detect variations in sharpness along the length of the blade. A graphical presentation showed that changes in cutting forces measured with the system correspond to changes in blade sharpness. Measurements made with both the test material and with red meat showed good correlation (r = 0.89). The system demonstrated the capacity to detect differences in sharpness in regions of a knife edge as well as providing visual evidence of defects along the edge of a knife blade.

Equipment Design↗

PubMed2005

Task-based estimation of mechanical job exposure in occupational groups.

OBJECTIVES: This study examined the validity of a common belief in epidemiology with respect to work-related musculoskeletal disorders, that individual mechanical job exposure is better estimated from tasks performed in the job than from the mean exposure of the occupational group. METHODS: Whole-day recordings of upper trapezius electromyography were obtained from 24 cleaners and 23 office workers. Trapezius activity was analyzed in the level (gap time) and frequency (jerk time) dimensions. On the same day, the job of each person was divided into periods of active work and breaks by means of continuous observations. The bootstrap re-sampling technique was used with this database to compare task-based job exposure estimates with estimates based on the occupational mean. For a particular person, the task-based estimate was obtained by combining the average work and break exposures in the occupation with the personal time proportions of the two tasks in the job. RESULTS: The task-based estimates were, in general, equivalent to, or less correct than, occupation-based estimates for both exposure parameters in both occupations and for individual exposures, as well as for group means. This was the result in spite of significant and consistent exposure differences between work and breaks, in particular among the cleaners. CONCLUSIONS: Even if task exposure contrasts are large, task-based estimates of job exposures can be less correct than estimates based on the occupational mean. Since collecting and processing task information is costly, it is recommended that task-based modeling of mechanical exposure be implemented in studies only after careful examination of its possible benefits.

Bias↗

PubMed2005

[Isometric muscle strength measurements and assessment: a pilot study].

OBJECTIVE: To determine the anthropometric parameters and the isometric muscle strength in a working population sample in China, and to investigate the relationship between muscle strength and individual attributes, such as age, gender, height and weight. METHODS: The study population consisted of 146 male and 47 female people including workers, administrators and college students. Four types of muscle strength, i.e., handgrip, arm lift, shoulder lift, and torso pull, were measured. RESULTS: Left handgrip, right handgrip, arm lift, shoulder lift and torso pull of male workers were (42.07 +/- 7.20), (43.92 +/- 7.14), (26.79 +/- 4.64), (33.79 +/- 6.88), (88.56 +/- 17.98) kg, respectively while those of female workers were (21.29 +/- 5.09), (23.26 +/- 5.47), (13.29 +/- 3.37), (18.52 +/- 4.01), (41.06 +/- 12.04) kg, respectively. The female's strength was about 50% lower than the male's. The strength in the 40 approximately years old group was higher than that in other age groups. There were significant positive correlation between the gender and the isometric strength as well as between the body weight and the isometric strength. If the body weight served as the corrected parameter, there was no significant difference in the handgrip among the groups (P < 0.05), but the torso pull of male workers > college students > administrators. All relative muscle strengths except the torso pull were similar for all age groups. CONCLUSION: The body weight as the independent variable can be used for establishing the predictive equation of the muscle strength. Calculation of the relative muscle strength can relieve the interference of the body weight for the muscle strength.

Adolescent↗

PubMed2004

The effect of blade finish and blade edge angle on forces used in meat cutting operations.

Meat cutting causes a much greater incidence of upper extremity disorders than industry averages. Grip forces and cutting moments in meat cutting operations can be very high. Recently published studies indicate that the blade sharpness can significantly affect force exposure during meat cutting. Two attributes that have not been investigated with respect to force exposure during meat cutting are the effect of blade edge angle and blade finishing after sharpening (honing and polishing). This study investigated the effect of three blade edge angles and three post-sharpening finishing protocols on the grip forces and cutting moments exerted by professionals during two different meatpacking operations. A fine polish finishing protocol significantly reduced cutting time by 25.3%, mean grip force by 21.2%, and mean cutting moment by 28.4% over a coarser finishing protocol during one of the operations. No significant differences in the exposure variables were found between the blade edge angle conditions.

Adult↗

PubMed2004

Practical aspects of functional capacity evaluations.

Physicians, employers, insurers, and benefits adjudicators often rely upon functional capacity evaluations (FCEs) to determine musculoskeletal capacity to perform physical work, often with legal or occupational consequences. Despite their widespread application for several decades, a number of scientific, legal, and practical concerns persist. FCEs are based upon a theoretical model of comparing job demands to worker capabilities. Validity of FCE results is optimal with accurate job simulation and detailed, intensive assessments of specific work activities. When test criteria are unrelated to job performance, or subjective evaluation criteria are employed, the validity of results is questionable. Reliability within a subject over time may be adequate to support the use of serial FCE data collection to measure progress in worker rehabilitation. Evaluation of sincerity of effort, ability to perform complex or variable jobs, and prediction of injury based upon FCE data is problematic. More research, especially studies linking FCE results to occupational outcomes, is needed to better define the appropriate role for these evaluations in clinical and administrative settings.

Humans↗

PubMed2004

The effect of force distribution and magnitude at the hand-tool interface on the accuracy of grip force estimates.

The ability to accurately estimate grip force requirements may be important in exposure assessment, determining fitness for duty, or setting rehabilitation goals. This study investigates the effects of learning and experience, measurement system, and the nature of the task on grip force estimate accuracy. The grip forces applied during "pure" power grip tasks and simulated meat cutting tasks conducted in the laboratory, and during meat cutting operations at meat packing plants were measured with an instrumented tool handle. Estimates were recorded using the tool handle and a modified hand dynamometer. The results indicate that estimate accuracy varied greatly from individual to individual. No significant effect of learning on estimate accuracy was observed. The result of the meat cutting simulation and field study suggest that the force distribution at the hand-tool interface can markedly affect estimates. Great care must be taken in the collection of grip force estimates, as well as in the interpretation of the data. Improved understanding of the factors affecting estimates of grip force requirements should aid in the interpretation of functional capacity evaluations, and in the establishment of goals for rehabilitation.

Adult↗

PubMed2004

The effect of workstation and task variables on forces applied during simulated meat cutting.

The purpose of the study was to investigate factors related to force and postural exposure during a simulated meat cutting task. The hypothesis was that workstation, tool and task variables would affect the dependent kinetic variables of gripping force, cutting moment and the dependent kinematic variables of elbow elevation and wrist angular displacement in the flexion/extension and radial/ulnar deviation planes. To evaluate this hypothesis a 3 x 3 x 2 x 2 x 2 (surface orientation by surface height by blade angle by cut complexity by work pace) within-subject factorial design was conducted with 12 participants. The results indicated that the variables can act and interact to modify the kinematics and kinetics of a cutting task. Participants used greater grip force and cutting moment when working at a pace based on productivity. The interactions of the work surface height and orientation indicated that the use of an adjustable workstation could minimize wrist deviation from neutral and improve shoulder posture during cutting operations. Angling the knife blade also interacted with workstation variables to improve wrist and upper extremity posture, but this benefit must be weighed against the potential for small increases in force exposure.

Adolescent↗

PubMed2004

Investigation of a pork shoulder deboning operation.

An ergonomic investigation of force exertions during pork shoulder deboning was conducted. Nine male workers volunteered to participate in the study. Three cycles of the shoulder deboning task were measured for each worker, using an instrumented knife that provided direct measurements of grip forces and cutting moments applied to the knife. The average grip force values during the task were between 11 and 35% of the maximum voluntary grip force. A key finding was that there is high between-subject variation in exposure to integrated grip forces and cutting moments, which can have implications for exposure to risk for upper extremity musculoskeletal disorders. There was also high between-subject variation in cutting time. Measures of knife sharpness indicated that there is also variation in knife maintenance among workers during a 5-hour period. The implications of the results for training and further study are discussed.

Adult↗

PubMed2004

Study on musculoskeletal disorders in a machinery manufacturing plant.

Musculoskeletal disorders and related risk factors in machinery manufacturing were investigated using interviews, postural analysis, and the revised National Institute for Occupational Safety & Health lifting equation. Sixty-nine workers involved in manual materials handling (Job A) and 51 machinery workers less involved with manual material-handling tasks (Job B) were studied. Low back pain (LBP) (at least one episode lasting for 24 hours or more in past 12 months) prevalence rates were 63.8% and 37.3% for Jobs A and B, respectively. Prevalence rates of LBP every day for a week or more attributed to lifting were 26.09% and 5.88% for Jobs A and B, respectively. Multiple regression analysis revealed that lifting repetitiveness and work age contributed to the occurrence of LBP. The "composite load" (object weight x activity repetitiveness) had a significant adverse effect on LBP.

Adult↗

PubMed2003

The effect of technique and shaft configuration in snow shoveling on physiologic, kinematic, kinetic and productivity variables.

A repeated measures 2 x 2 factorial design using a psychophysical experimental methodology was performed to quantify the effect of shaft design (straight and bent shaft) and shoveling technique (forward and backward progression) on heart rate, perceived exertion, productivity, trunk kinematics and load kinetics. Ten male subjects performed four 8-min trials of snow shoveling on a paved asphalt surface. The most notable finding was significantly less trunk flexion with the bent shaft (41.4 degrees ) than with the straight shaft design (49.2 degrees ). The study results led to a recommendation of a bent-shaft shovel for the purpose of reducing trunk flexion. In the absence of any strong positive evidence and due to poor subjective response to backward progression while shoveling, this technique was not recommended.

Biomechanical Phenomena↗

PubMed2003

Cutting moments and grip forces in meat cutting operations and the effect of knife sharpness.

The force exposure associated with meat cutting operations and the effect of knife sharpness on performance and productivity have not been well documented. Specialized hardware was used to measure grip force and reactive moments with 15 professional meat cutters performing lamb shoulder boning, beef rib trimming and beef loin trim operations in a field study conducted in two meat packing plants. A system for measuring relative blade sharpness was developed for this study. Mean and peak cutting moments observed for the meat cutting operations, averaged across subjects were 4.7 and 17.2 Nm for the shoulder boning, 3.5 and 12.9 Nm for the rib trim, and 2.3 and 10.6 Nm for the loin trim, respectively. Expressed as percent of MVC, mean grip forces of 28.3% and peak grip forces of 72.6% were observed overall. Blade sharpness was found to effect grip forces, cutting moments and cutting time, with sharper blades requiring statistically significantly lower peak and mean cutting moments, and grip forces than dull knives. Efforts aimed at providing and maintaining sharp blades could have a significant impact on force exposure.

Abattoirs↗

PubMed2002

Usability of the revised NIOSH lifting equation.

Following the revision of the 1981 National Institute for Occupational Safety and Health (NIOSH) lifting equation, research needs related to the new equation were outlined. Aside from epidemiological studies, the need to evaluate the usability of the 1991 NIOSH equation in realistic work environments was expressed. This paper reports on extensive experiences with training users and application of the equation in varied work settings. Qualitative results from training sessions indicated that frequency, asymmetry and duration were the parameters that required relatively longer instruction periods and resulted in the most questions. Field applications indicated that the variable nature of lifting/lowering demands found in many jobs resulted in difficulty applying the equation. Approximately 35% of 1103 lifting and lowering tasks had at least one parameter outside of acceptable ranges, while a majority of workers (62.8%) reported other manual handling tasks that are counter to assumptions made in the development of the equation. The practical implications of the findings are discussed.

Guideline Adherence↗

PubMedDate not supplied

Bending the tool and the effect on human performance: further investigation of a simulated wire-twisting task.

A previous experiment by the authors investigated the effect of the design of pliers on productivity. A simulated wire-twisting task performed at five heights between 10 inches above and 10 inches below elbow height formed the basis of the comparison. Pliers designed according to the American National Standard for long nose and long reach pliers were compared to bent-handled pliers designed at the Western Electric (WE) Co. The WE pliers, designed to reduce ulnar deviation during a wire-twisting task, resulted in productivity decrements between 1.4 and 17% across the five heights studied. The current experiment was a continuation of that study, adding orientation of the workplace in the sagittal plane as an independent variable. Wrist deviation in two planes were additional dependent measures, and the experiment was performed by female subjects with a mean age of 48.1 years. The results did not indicate a significant difference between productivity levels for the two pliers designs. Work height and work orientation, as well as their interaction, tended to have the strongest effects on productivity and wrist deviation. In general, productivity was inversely related to measures of discomfort and postural deviation.

Adult↗

PubMedDate not supplied

Maximal acceptable torques of highly repetitive screw driving, ulnar deviation, and handgrip tasks for 7-hour workdays.

This study represents a continuation of a series of psychophysical studies on repetitive motions of the wrist and hand conducted at the Liberty Mutual Research Center for Safety and Health. The purpose of the study was to quantify maximum acceptable torques of six motions performed on separate days but within the context of the same experiment. The six motions were screw-driving clockwise with a 31-mm handle, a 40-mm handle, and a 39-mm yoke handle; screw-driving counterclockwise with a 31-mm handle; ulnar deviation with a power grip (similar to knife cutting), and a handgrip task (similar to a pliers task). A psychophysical methodology was used in which the subject adjusted the resistance on the handle, and the experimenter manipulated or controlled all other variables. Ten subjects performed the six tasks at repetition rates of 15, 20, and 25 motions per minute. Subjects performed the tasks for 7 hours per day, 5 days per week, for 4 weeks. The subjects were instructed to work as if they were on an incentive basis, getting paid for the amount of work they performed. Symptoms were recorded by the subjects during the last 5 min of each hour. The results revealed that mean maximum acceptable torques ranged from 0.33 to 0.65 Nm for screw driving, 1.08 to 1.13 Nm for ulnar deviation, and 4.80 to 4.85 Nm for the handgrip task. These values represent 14 to 24% (median of 17%) of maximum isometric torque depending on the frequency and motion. A table of maximum acceptable torques and forces of the six motions is presented for application in the field.

Adult↗