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Biomedical subjects

D B Chaffin

Publications and source records attributed to D B Chaffin.

At least 73 records · Page 4Linked to original sources
PubMed1984

A dynamic biomechanical evaluation of lifting maximum acceptable loads.

A biomechanical evaluation of the job-related stresses imposed upon a worker is a potential means of reducing the high incidence rates of manual material handling injuries in industry. A biomechanical model consisting of seven rigid links joined at six articulations has been developed for this purpose. Using data from cinematographic analysis of lifting motions the model calculates: (1) body position from articulation angles, (2) angular velocities and accelerations, (3) inertial moments and forces, and (4) reactive moments and forces at each articulation, including the L5/S1 joint. Results indicated effects of the common task variables. Larger load and box sizes increased the rise times and peak values of both vertical ground reaction forces and predicted L5/S1 compressive forces. However, boxes with handles resulted in higher L5/S1 compressive forces than for boxes without handles. Also, in lifting the larger boxes the subjects did not sufficiently compensate with reduced box weights in order to maintain uniform L5/S1 compressive forces. Smoothed and rectified EMG of erector spinae muscles correlated significantly with L5/S1 compressive forces, while predicted and measured vertical ground reaction forces also correlated significantly, indicating the validity of the model as a tool for predicting job physical stresses.

Humans↗
PubMed1983

Quantification of human performance circadian rhythms.

The quantification of worker performance changes during a shift is critical to establishing worker productivity. This investigation examined the existence of circadian rhythms in response variables that relate most meaningfully to the physiological and neurological state of the body for three subjects maintaining a resting posture for 25 hours on five separate occasions. Significant circadian variation ranging from 3% to 11% of the mean value was detected for elbow flexion strength, physiological tremor, simple reaction time, information processing rate and critical eye-hand tracking capacity.

Adult↗
PubMed1981

Functional assessment for heavy physical labor.

It is proposed that assessment of a worker who performs manual labor must include specific tests of physical capability. Such tests must meet certain criteria to be accepted as medically, economically and legally justified. The medical and economic justification for such tests is recognized by all concerned with controlling the excessive costs and human suffering associated with over-exertion strain/sprain injury and illness in industry. The legal basis for such tests is not well established and will not exist until a documented history of success or failure is developed in the courts for different types of tests. It is hoped that as various tests are developed by medical departments the criteria stated in the first part of this article will be of assistance. As to the status of isometric strength testing for employee selection and placement, it is being implemented as part of the medical examination in a number of large industries as an experimental medical procedure. Data are being continually gathered to further validate and refine the procedures. It is discussed in this contest as one of several methods which needs to be considered and evaluated to reduce musculoskeletal injury and illness in industry.

Accidents, Occupational↗
PubMed1980

Static work elements and selected circulatory responses.

It has been recommended that circulatory responses be used as measures of circulatory stress and as a basis of work-rest scheduling. The purpose of this paper is to show how statistical models can be developed and used to describe selected circulatory responses associated with static work elements. Heart rate, mean arterial pressure and cardiac work were modeled as functions of work duration and intensity for four subjects performing sustained static group exertions to exhaustion at 12.5%, 25%, 50% and 75% of maximum strength. Examples and considerations of predicted circulatory responses to static work elements are discussed.

Blood Pressure↗
PubMed1980

Establishing an industrial strength testing program.

This study was performed to develop and evaluate a scheme for matching the strength of workers to the strength demands of their jobs. Biomechanical analyses were performed on production jobs in an aluminum reduction plant to identify and quantify strength demands. These data were used to design a set of nine strength tests which simulated job activities with the greatest strength requirements. A cross section of plant employees assigned to these jobs was strength tested and monitored for medical incidents for a period of over two years. Significant relationships were found among job strength requirements, worker strengths, and medical incidents. Workers with strength abilities (as determined by the tests) less than job strength requirements suffered a higher rate of medical incidents than workers whose strength abilities matched or exceeded job demands. It was concluded that strength testing can be used to identify workers who would be at increased risk of suffering medical incidents if placed on jobs which exceeded their strength abilities.

Adolescent↗
PubMed1980

Isometric strength testing as a means of controlling medical incidents on strenuous jobs.

This investigation was performed to determine if isometric strength tests can be used to select workers for strenuous jobs and to reduce occupational injuries which are caused by a mismatch between worker strength and job strength requirements. Twenty jobs in a tire and rubber plant were studied biomechanically to identify critical strength-demanding tasks. Four strength tests were designed to simulate these tasks, and performance criteria were established for passing the tests. New applicants were administered the tests during their preplacement examinations to determine if they possessed sufficient strength to qualify for the jobs. The medical incidence rate of employees who were selected using the strength tests was approximately one-third that of employees selected using traditional medical criteria. It was concluded that isometric strength tests can be used to reduce occupational injuries and should be considered for implementation in industries with strenuous jobs.

Accidents, Occupational↗
PubMed1979

Carpal tunnel syndrome and selected personal attributes.

Carpal tunnel syndrome has been reported to occur between two and ten times as frequently in women as in men. It also has been reported that this syndrome is often associated with the performance of certain manual tasks. Such cases can be considered an occupational disease. This study was addressed to the question: Why do some people develop carpal tunnel syndrome while others do not? Two matching female populations, one with a known history of carpal tunnel syndrome and one without a known history of carpal tunnel syndrome, were selected and differences in hand size and work methods were studied. Both populations were employed in the same production sewing jobs. While differences in hand size were not found, use of forceful exertions and of deviated wrists and pinch hand position - particularly during forceful exertions - were found to be associated with carpal tunnel syndrome.

Adult↗
PubMed1978

Prediction of metabolic rates for manual materials handling jobs.

A mew approach for estimating metabolic rates for manual materials handling jobs is presented. This approach was applied to 48 different jobs. The model validation showed a correlation coefficient of 0.95 between the measured and predicted metabolic rates. The coefficient of variation (standard error/sample mean) was 10.2 percent.

Adult↗
PubMed1978

Evaluation of workers exposed to elemental mercury using quantitative tests of tremor and neuromuscular functions.

Workers exposed to metallic mercury vapor were subjects for tremor, EMG, and psychomotor tests. Regression analysis revealed statistically significant trends in these test results related to workers' urine mercury histories. Effects were subclinical, functionally insignificant and most associated with those workers whose urine mercury had exceeded 0.5 mg/L in the previous year. In agreement with previous reports, effects were reversible upon reduction of mercury exposure.

Adult↗
PubMed1978

Personalized, electro-kinematic, neuromuscular model of a human forearm.

Electromyography, the recording of muscular activity, is of importance in industrial, biomechanical, and sports research as well as in medical diagnoses. When a muscle is activated, an electric potential in the order of microvolts (muV) is generated. This potential can be picked up, amplified, and displayed on an oscilloscope or strip chart recorder. Researchers have developed ways of analyzing these signals in terms of their characteristics. A numerical index, which reflects the basic characteristics of the electromyogram, mainly amplitude, frequency, and duration, can be used to provide quantitative information. The method used in this work for EMG processing consisted of filtering, rectification, and integration over very small intervals of time. Both analog and digital filtering proved necessary. Angular accelerometer and rotational potentiometer data were used in conjunction with limb inertia parameters obtained from existing biochemical models for the individual tested for obtaining the torques as a function of time. A system parameter identification method was used to determine the muscle parameters, such as occur in the single muscle Hill model, of four muscle groups for a human arm. The main results consist of personalized arm muscle group models. It was concluded that the method provided excellent (fit) personalized arm muscle group models under dynamic conditions. This method could lead to fundamental scientific information about a living muscle group from experiments in vivo.

Electromyography↗