Working Postures of Dentists and Dental Hygienists

A joint study was conducted by a manufacturer of dental stools in the Midwest of the United States and Marquette University to measure the occupational postures of dentists and dental hygienists. The postures of 10 dentists and 10 dental hygienists were assessed using work sampling and video techniques. Postura! data of the neck, shoulders and lower back were recorded from video and categorized into 30-degree intervals: O (neutral posture of respective joint), 30, 60 and 90 degrees. Each subject\u27s postures were observed while they were treating patients during a four-hour period, during which 100 observations of postures were recorded at random times. Compared to standing, dentists and dental hygienists were seated 78 percent and 66 percent of the time, respectively. Dentists and dental hygienists flexed their trunk at least 30 degrees more than 50 percent of the time. They flexed their neck at least 30 degrees 85 percent of the time during the four-hour duration, and their shoulders were elevated to the side of their trunk (abducted) at least 30 degrees more half of the time. The postures of the trunk, shoulders, and neck were primarily static. This database of postures can be used by dental professionals and ergonomists to assess the risk dentists and dental hygienists are exposed to musculoskeletal disorders, such as low back pain or shoulder tenosynovitis, from deviated joint postures. They could use these data to select dental furniture or dental devices that promote good body posture, i.e., reduce the magnitude and duration of deviated joint postures, which, in theory, would decrease the risk of musculoskeletal disorders

Effect of Setup Configurations of Split Computer Keyboards on Wrist Angle

Alternative computer keyboards whose halves can be slanted toward each other can reduce a risk factor (ulnar deviation) for work-related musculoskeletal disorders (WMSDs) affecting the upper limbs. Two questions that computer keyboard operators face when using keyboards that can be separated into halves (split keyboards) are: (1) At what angle should the keyboard halves be opened? and (2) At what distance apart should the keyboard halves be placed? The objective of this study was to investigate the effects of the opening angle and separation distance between halves of a split keyboard on wrist ulnar deviation and typing efficiency. Methods. Eleven experienced computer keyboard operators participated in this study and used a split keyboard that was set up in a conventional (nonsplit) format and also in 3 alternative configurations: (1) centers of keyboard halves were separated at 20-cm distance, (2) keyboard halves were separated half of the distance of shoulder width, and (3) keyboard halves were separated at shoulder width distance. Results. The 3 alternative configurations resulted in ulnar deviation of both wrists that were less than ulnar deviation from typing on a conventional setup. There were no differences in ulnar deviations among the 3 alternative configurations. Discussion and Conclusion. The results of this research provide physical therapists and ergonomists with a set of configurations of a split keyboard that they can recommend to their patients or clients. All of the alternative configurations of the split keyboard are beneficial in promoting a neutral wrist position, which theoretically would decrease exposure to WMSDs such as tenosynovitis in the wrist and carpal tunnel syndrome. [Marklin RW, Simoneau GG. Effect of setup configurations of split computer keyboards on wrist angle. Phys Ther. 2001;81:1038 –1048.

Evaluation of Forearm Muscle Fatigue from Operating a Motorcycle Clutch

A laboratory experiment evaluated the effect of motorcycle clutch design on the electromyography (EMG) activity of the primary agonist finger flexor muscle in the forearm. The goal was to compare muscle fatigue resulting from operation of two different motorcycle clutches in simulated traffic. EMG activity from the flexor digitorum superficialis (FDS) muscle of 12 female and 11 males were recorded while each participant operated an existing motorcycle clutch (requiring 98 N peak force) as well as an alternate design (requiring 36 N peak force) during 60-minute simulations. Muscle fatigue was quantified by measuring the decrease in median frequency of the EMG signals. Compared to operating the existing clutch, male participants experienced a significant decrease in muscle fatigue between 14 to 31% when operating the alternate clutch. Females experienced a decrease of 27 to 49%. In addition to reduced muscle fatigue, the alternate clutch was overwhelmingly preferred by participants and was rated superior for ease of use and comfort. Results provide a better understanding of the effect of clutch design on riders’ muscular loading and implications for design improvements

Business Case for Implementing Two Ergonomic Interventions at an Electric Power Utility

Ergonomics analysis of line workers in the electric power industry who work overhead on utility poles revealed some tasks for which less than 1% of the general population had sufficient strength to perform. During a 2-year study, a large Midwestern US electric utility provided a university with a team of represented workers and management. They evaluated, recommended, and monitored interventions for 32 common line worker tasks that were rated at medium to high magnitude of risk factors for musculoskeletal disorders (MSDs). Two of the recommended ergonomic interventions—the battery-operated press and cutter—were selected by the team as having the greatest potential for reducing risk factors of MSDs. Only overhead distribution line worker tasks were evaluated. A business case was formulated that took into account medical injury and illness statistics, workers’ compensation, replacement worker and retraining costs. An outline of a business case formulation and a sample intervention payback calculation is shown. Based on the business case, the utility committed over $300,000 to purchase battery-operated presses and cutters for their overhead distribution line crews

A Shovel With a Perforated Blade Reduces Energy Expenditure Required for Digging Wet Clay

Objective: A shovel with a blade perforated with small holes was tested to see whether a worker would use less whole-body energy to dig wet clay than with a shovel with an opaque blade. Background: A perforated shovel is hypothesized to require less whole-body energy on the basis of adhesion theory; a smaller surface area would require less physical effort to dig and release soil from the blade. Method: The study involved 13 workers from an electric utility who dug wet clay with two 1.5-m long-handled point shovels, which differed only in blade design (perforated and opaque). Oxygen consumption was measured with a portable system while each worker dug wet clay at a self-regulated pace for 10 min. Results: There was no significant difference in number of scoops dug during the 10-min sessions, but workers dug 9.5% more weight of clay with the perforated shovel than with the conventional shovel (404 kg vs. 369 kg, respectively). Furthermore, stable oxygen uptake normalized to weight of participant and to the weight of clay dug revealed that participants expended 11.7% less relative energy per kilogram of clay dug with the perforated shovel. Conclusion: A point shovel with a perforated blade is recommended for digging and shoveling wet clay. However, the extra weight that workers chose to dig with the perforated shovel may increase the loading on the spine and may offset the metabolic advantages. Application: Manual shoveling is a common task, and workers may experience less whole-body and muscle fatigue when using a perforated shovel

Effect of Computer Keyboard Slope on Wrist Position and Forearm Electromyography of Typists Without Musculoskeletal Disorders

Positioning a computer keyboard with a downward slope reduces wrist extension needed to use the keyboard and has been shown to decrease pressure in the carpal tunnel. However, whether a downward slope of the keyboard reduces electromyographic (EMG) activity of the forearm muscles, in particular the wrist extensors, is not known. Subjects and Methods. Sixteen experienced typists participated in this study and typed on a conventional keyboard that was placed on slopes. Electromyographic activity of the extensor carpi ulnaris (ECU), flexor carpi ulnaris (FCU), and flexor carpi radialis (FCR) muscles was measured with surface electrodes, while the extension and ulnar deviation angles of the right and left wrists were measured with electrogoniometers. Results. Wrist extension angle decreased from approximately 12 degrees of extension while typing on a keyboard with a 7.5-degree slope to 3 degrees of flexion with the keyboard at a slope of –15 degrees. Although the differences were in the range of 1% to 3% of maximum voluntary contraction (MVC), amplitude probability distribution function (APDF) of root-mean-square EMG data points from the ECU, FCU, and FCR muscles varied across keyboard slopes. Discussion and Conclusion. Wrist extension decreased as the keyboard slope decreased. Furthermore, a slight decrease in percentage of MVC of the ECU muscle was noted as the keyboard slope decreased. Based on biomechanical modeling and published work on carpal tunnel pressure, both of these findings appear to be positive with respect to comfort and fatigue, but the exact consequences of these findings on the reduction or prevention of injuries have yet to be determined. The results may aid physical therapists and ergonomists in their evaluations of computer keyboard workstations and in making recommendations for interventions with regard to keyboard slope angle. [Simoneau GG, Marklin RW, Berman JE. Effect of computer keyboard slope on wrist position and forearm electromyography of typists without musculoskeletal disorders. Phys Ther. 2003;83:816–830.

Using Remote Access for Sharing Experiences in a Machine Design Laboratory

A new Machine Design Laboratory at Marquette University has been created to foster student exploration and promote “hands-on” and “minds-on” learning. Laboratory experiments have been developed to give students practical experiences and expose them to physical hardware, actual tools, and design challenges. Students face a range of real-world tasks: identify and select components, measure parameters (dimensions, speed, force), distinguish between normal and used (worn) components and between proper and abnormal behavior, reverse engineer systems, and justify design choices. The experiments serve to motivate the theory, spark interest, and promote discovery learning in the subject of machine design. This paper presents details of the experiments in the Machine Design Laboratory and then explores the feasibility of sharing some of the experiences with students at other institutions through remote access technologies. The paper proposes steps towards achieving this goal and raises issues to be addressed for a pilot-study offering machine design experiences to students globally who have access to the internet

Freehand Sketching for Engineers: A Pilot Study

This paper describes a pilot study to evaluate Freehand Sketching for Engineers, a one credit, five week course taught to undergraduate engineering students. The short-term goal of this course was to improve engineering students’ freehand sketching ability and to assess their progress with metrics. The long-term objective (desired learning outcome) of this course is to improve the creativity and innovation of student design projects by enhancing students’ ability to visualize their ideas with freehand sketches. The class met two days a week for 75 min per day. Students were taught to draw simple objects such as electrical boxes, with orthographic, isometric, and oblique views on 8 ½ x 11 in. sheets of blank paper (no grid lines) and wooden #2 pencils. No instruments, such as rulers and compasses, were allowed. The course required students to apply what they learned in the classroom and included many examples of hands-on, active and student-centered learning activities. Two assessments were performed to measure whether students improved their ability to freehand sketch. The first involved two outside reviewers (industrial designers) who evaluated each student’s sketch of a pipe fitting that was drawn in the first class (pre-test) and a sketch of the same pipe fitting in the eighth class (after 7 hours of instruction - post-test). Sketches were evaluated using a 1 (poor) to 7 (excellent) Likert scale. The second assessment consisted of an evaluation of the final projects, which were a collection of five sketches with different views of an engineered product. Evaluations of the pre- and post-test drawings and the final projects by outside reviewers and positive observations by engineering faculty suggest that this course has the potential to improve students’ ability to sketch objects. This paper discusses details of the course, provides examples of student sketches, and presents results of outside reviewer assessments. It includes suggestions for a more rigorous assessment of the course to determine its potential to improve students’ ability to sketch objects

Aquaponics: A Sustainable Food Production System That Provides Research Projects for Undergraduate Engineering Students

Aquaponics is a closed-loop, recirculating water system in which plants and fish grow together mutualistically. Aquaponics resembles a natural river or lake basin in which fish waste serves as nutrients for the plants, which in turn clean the water for the fish. Tilapia and salad greens or herbs are common fish and plants grown in an aquaponics system. The external inputs to an aquaponics system are fish food, minimal amount of water, and energy for lighting and heating the water for the fish and plants. Aquaponics is a sustainable, efficient system to raise fish protein and vegetables for human consumption. Aquaponics systems can be located anywhere in the world where there is adequate energy with a minimal amount of water. Aquaponics is particularly suited to arid climates because it uses much less water to grow plants than soil-based systems. In fact, the only water that is lost is evaporation and transpiration from the plants. Although the field of aquaponics is growing world-wide, the capital and operational costs of producing the plants and fish have not been quantified intensively in the peer-reviewed literature. The relationship between the amount of external energy (fish food plus energy for light and heat) to the output (weight of fish and plants) has not been measured well for aquaponics units in temperate climates. The lack of quantification of the input-output has suppressed aquaponics progress because it is difficult to compare the cost of fish and salad greens grown with aquaponics and conventional methods, such as aquaculture and soil-based methods. The diverse nature of aquaponics and the need to quantify the relationship between input-output presents opportunities for research projects for undergraduate engineering students in Mechanical, Electrical, and Civil Engineering. The following are examples: Sensors: What type of sensors are ideal to measure air and water temperature, water PH, dissolved O2, and nitrates? Thermodynamics: What type of water heating system is most efficient to maintain desirable water and air temperature? Water Quality: What are the optimal methods to filter out the solid fish waste (feces) and introduce necessary bacteria into the system? Hydraulics: What size of pump and diameter of pipe are needed to maintain optimal flow rate? System Design: What are the optimal ratios between fish tank volume and grow area volume? What is the optimal drop in water level between components to utilize the gravity system? Marquette University College of Engineering is building a laboratory to conduct aquaponics research. The design of the system along with the lessons learned will be presented, along with a detailed list of specific projects for engineering students. Lessons learned from this research will aid the development of aquaponics in temperate climates but also possibly in subtropical and tropical region

Measurement of Handle Forces for Crimping Connectors and Cutting Cable in the Electric Power Industry

Overhead and underground line work in the electric power industry is physically very strenuous and can expose workers to musculoskeletal disorders (MSDs), particularly in the upper extremity. Crimping compression connectors—such as sleeve connectors and lugs—and cutting cables are two of the most frequent tasks that line workers perform. Line workers at many utilities in the US crimp connectors and cut cable with long-handled manual tools. However, the actual magnitude of the forces applied to the handles of these tools is not known. The objectives of this laboratory study were to measure the forces applied to the handles of a manual press and a manual cutter in order to connect typical wire gauges and cut common cables, respectively. The handles of the manual press and cutter were attached to the drive cylinder and load cell of an Instrom Material Testing System, and peak forces exerted against the handles were measured. Results showed that the outer die of the manual press required about 50% more handle force than crimping connectors with the inner die location. The peak handle forces required to cut aluminum conductor cable as large as 2 cm diameter exceeded 500 N and were about 200 N greater than the peak forces to compress connectors manually. When the peak force data were compared to strength capabilities reported in the literature, less than 1% of the general population was found to have the maximum strength to manually make one crimp on a common overhead connector. Less than 1% and approximately 50% of the female and male general population, respectively, were found to have the maximum strength to manually cut a cable with a 2 cm diameter conductor. Handle force data from this study provide a biomechanical framework for explaining how the job demands of overhead and underground line workers could possibly cause MSDs. Relevance to industry Electric power utilities can review their work practices and tools in order to determine whether they can reduce the exposure of their workers to risk factors of MSDs, as well as reduce their cost of health care. Manufacturers of crimping and cutting tools can use the experimental approach in this study to measure the external forces required for their respective tools and then set quantitative force benchmarks to improve the design of their tools