Robert J. Marley

An improved musculoskeletal discomfort assessment tool

Abstract A self-report musculoskeletal assessment tool was adapted following field use by ergonomic analysis teams and was administered to 797 employees of a public utility company. Results were analyzed to determine if the self-reports could adequately predict whether or not an employee reportedly sought medical or therapeutic treatment for a work-related discomfort. A discriminant analysis was used to show that the ratings could identify those who had sought treatment. Tabulation of a joint frequency distribution of the ratings (Discomfort Level × Frequency of Discomfort) and discriminant function probabilities resulted in a convenient separation of the population into three “zones”. These zones were labeled: (1) “very likely”, (2) “somewhat likely”, and (3) “not likely” to seek treatment. This tool is not intended to be a diagnostic instrument since the criterion was not a specific cumulative trauma diagnosis. Rather, it can be utilized as an easily administered, proactive surveillance instrument to assist in early identification of ergonomic concerns and to help prioritize jobs for intervention. Relevance to industry An easy to administer, self-reporting discomfort tool was developed and validated based upon a large industrial population. It is anticipated that this tool will be useful in auditing and surveillance for musculoskeletal disorders. It may be particularly useful in prioritizing ergonomic intervention for these disorders.

Grip Strength as a Function of Forearm Rotation and Elbow Posture

An investigation was performed to assess the effect of forearm rotation (pronation and supination) and elbow orientation upon maximum grip strength of 10 male and 10 female subjects. Seven positions of forearm rotation which ranged from 90 degrees pronation to 90 degrees supination in both the 90 degree elbow flexion (arm adducted, forearm horizontal) and 0 degree flexion (shoulder flexed, whole-arm extended forward and horizontal) postures were examined. Thus a total combination of 14 postures were documented. Results indicate that maximum grip strength decreased significantly with forearm pronation, relative to the “neutral” forearm posture (p = 0.086). Other rotation postures did not yield significantly different grip strength from the neutral, but there was a clear decreasing trend in grip strength with forearm rotation away from neutral, particularly in pronation. The 0 degree elbow flexion showed the highest average grip strength values compared to 90 degree elbow flexion postures. Also, in the 90 degree elbow flexion posture, grip strength tended to increase with some supination from neutral rotation. It is recommended that for repetitive grasping activities, the arm and forearm postures should be considered in evaluating maximum grip strength. A regression model is presented to estimate maximum grip strength as a function of forearm rotation and elbow posture.

ErgoCAD: an ergonomic CAD system

Abstract E-CAFFS is a rule-based expert system for fixturing on a CAD system using flexible fixtures. It accomplishes the automatic layout of fixture models on a CAD/CAM system for given applications through an interative process. The final fixtured simulation is graphically represented as solid models on the screen of a computer-aided design system. This paper focuses on the fixturing of planar polyhedral workpieces for face-milling operations and predicts the feasibility of a generalized expert fixturing strategy on CAD systems. The software developed as a result of this research has decreased fixturing costs by a substantial amount and has successfully reduced fixturing down-time to a mere fraction.

Effects of industrial back supports on physiological demand, lifting style and perceived exertion

Abstract The industrial back support has seen widespread and increasing use in manual material handling activities in recent years. This paper reports the results of a laboratory investigation in which subjects performed manual lifting of 7 and 14 kg loads at frequencies of 3, 6, and 9 lifts/minute. The six lifting task combinations were repeated under both with-support and without-support conditions while a total of 17 physiological, kinematic, and psychophysical variables were recorded. Based upon analysis, several general conclusions were reached: (1) with the exception of blood pressure, industrial back supports did not affect physiological responses, including energy expenditure, during lifting; (2) significant increases in blood pressure (both systolic and diastolic) while wearing a back support may present long-term health concerns for some worker populations; (3) lifting style in the sagittal plane was not altered by the support; and (4) subjects did not perceive less effort in lifting with a back support versus without. Overall, these results suggest that the demands of lifting are not reduced with the use of an industrial back support. The lack of rationale for the use of these devices based upon ergonomic criteria should call into question the continued prescription of the devices under the presumption of hazard control.

Isokinetic strength characteristics in wrist flexion and extension

Abstract A laboratory experiment was conducted to measure strength characteristics in dynamic (isokinetic) wrist flexion and extension. Twenty four college-age males exerted their maximum torque in both concentric flexion and extension at 60, 120, and 180°/s of angular velocity through a ±60° range of deviation from wrist neutral. Results show that velocity and motion direction significantly effected both peak torque as well as the postural displacement of peak torque. The value of peak torque decreased with an increase in velocity and the wrist angle at peak torque generally moved to a more deviated, flexed posture (from neutral) with increasing velocity as well. Peak torque for all velocity and motion-type conditions tested occurred in a flexed posture relative to neutral. It is anticipated that these results may be of use as biomechanically based considerations in the evaluation and design of upper extremity tasks involving wrist flexion/extension as well as to perhaps give insight into functional characteristics of the wrist. Finally, regression equations were developed to aid in the prediction of peak torque based upon task, individual and/or population parameters. Relevance to industry Results from this study should enhance the overall understanding of wrist functioning. Specifically, motion type, velocity of movement and wrist posture are important ergonomic design considerations. These results can also be used to modify existing biomechanical models that do not consider wrist variables.

Isokinetic Wrist Strength of Females with Carpal Tunnel Syndrome

An experiment was conducted to determine isokinetic wrist flexion and extension strengths of females diagnosed with carpal tunnel syndrome (CTS). Static strength measures were also documented. These values were compared to values from a matched control group. Results show a significant reduction in isokinetic wrist flexion force, grip and tip pinch strengths within the CTS group compared to the controls. Range of motion in wrist flexion also showed a significant decrement for the CTS group. Finally, regression models were developed to predict isokinetic strength based upon static measures.

Lifting Physical Work Capacity as a Function of Frequency

A laboratory experiment using 15 male subjects was conducted to document lifting physical work capacity over the frequency range of 2 to 12 lifts per minute and to compare these values to bicycling physical work capacity. Results indicate that bicycling PWC is significantly higher than lifting PWC at the 0.05 level. A variation in lifting PWC as a function of frequency was observed. This could be attributed to lifting technique. Task design should, therefore, not only consider lifting PWC but also the frequency of lift.

A Study of Several Performance Measures of Workers with Carpal Tunnel Syndrome

Objective measures of anthropometry, strength, range-of-motion, muscle activity, and task performance, and subjective ratings of pain were observed in a group of individuals diagnosed with carpal tunnel syndrome (CTS). These measures were compared to a control population showing no symptoms of CTS. Results indicate that individuals with CTS had significantly lower values on some strength tests, less range of motion on several measures, and reduced performance on a simulated task than did the control group. Ratings of pain and distress for the CTS group were also significantly higher than the control group. Occupational and personality factors associated with the CTS group were also identified and discussed.

Work in progress: An International Engineering: Certificate: Incentivizing engineering students to pursue global experiences

An innovative, easy to implement International Engineering Certificate is introduced in this work-in-progress, innovative practice paper. The certificate enhances a four year engineering or computer science major without delaying the time to graduate. Other benefits include low cost, flexible structure, appeal to diverse audiences and potential for external support opportunities. The certificate is compared to four international opportunities provided by other engineering programs.

The Role of Physical Ergonomics in Litigation

The primary goal of the ergonomist is to develop systems and products that increase productivity, function intuitively, and minimize the user’s risk of injury and illness. Injuries occur when a system or product does not fit or was not designed for the capabilities of the user. The physical ergonomist plays an important role in litigation in reducing the risk of large damages or settlements through improved design. This article outlines three cases that demonstrate how a physical ergonomist uses established methods and techniques to analyze litigation cases.