Browsing by Subject "Lifting and carrying"
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Item A Computerized Dynamic Biomechanical Simulation model for Sagittal Plane Lifting Activities(Texas Tech University, 1995-08) Lin, Chiuhsiang JoeThe biomechanical approach provides estimation of various mechanical stresses acting on the body while a person manually handles an object. Today, photographical motion systems are available for dynamic biomechanical research; however, studies using such systems are mostly performed in the laboratory due to high cost of the equipment and the expertise required in using them. Industrial ergonomists do not have much access to dynamic analyses. To provide ergonomists with a computerized dynamic job analysis tool, a sagittal plane lifting biomechanical simulation model was developed. The model simulates the dynamic motion of lifting tasks for the five body joints: the elbow, shoulder, hip, knee, and ankle. The inputs of the model include initial and final joint postures; subject's sex, weight, and height; weight of load; lifting height; and box dimensions. On output, the angular trajectories of the five joints are predicted. The motion of the lift is completely predicted by the model without any video inputs. The simulation model contains three computation units, the dynamics computation, the trajectory formation, and the optimization unit. The dynamics unit calculates the kinematics and kinetics. The trajectory formation unit uses numerical techniques to generate smooth joint trajectories. The optimization unit consists of an objective function and several constraints that describe the behavior of the human lifting. The simulation model was validated using actual lifting data from five male and five female subjects. The lifting tasks included floor-to-knuckle and floor-to-shoulder height lifts. Comparisons were made between the actual lifting motion and predicted motion. The results showed that the simulated motion followed the actual motion closely Sensitivity analysis showed that the optimization constraints had significant effects on the prediction performance of the simulation model.Item A fuzzy sets based model of the interaction between stresses involved in manual lifting tasks(Texas Tech University, 1982-12) Karwowski, WaldemarThe primary objectives of this research were: 1. Development and testing of a mathematical, fuzzy sets based model for the acceptability of the stresses involved in lifting activity. 2. Evaluation of the hypothesis that a combination of the acceptability of the biomechanical and physiological stresses leads to an overall measure of lifting task acceptability, namely the acceptability of the psychophysical stress. 3. Development of a general criterion for establishing maximum permissible weights of load to be lifted safely. 4. Comparison and evaluation of existing recommendations versus this proposed general criterion. The group of acceptable weights of load that can be lifted safely was defined as a class with no sharp transition from membership to nonmembershlp. The acceptability measure of the stresses were associated with fuzziness, rather than randomness. Measures of acceptability were expressed by membership functions which describe the degree to which the stresses were acceptable for the human operator (with respect to the chosen design criteria). A synergistic effect was used as the basis to combine the biomechanical and physiological stresses into one category. The psychophysical methodology was used to carry out an experiment with nine male subjects to provide the data needed for the model development. An iterative procedure was used to generate conditions for membership functions which resulted in the minimum (or near-minimum) mean value of the Hamming distance between the acceptability measures of these stresses. The combined stress was then compared with the psychophysical one using the similarity measure between them. The conditions under which the acceptability of the psychophysical stress were similar to the acceptability of the combined stress were found. The points of reference for the biomechanical stress where the hypothesis holds true were also deterniined. A general criterion for the acceptability of the lifting task was proposed as one which considers the effect of both biomechanical and physiological stresses on the human operator's performance during manual lifting activities.Item A predictive model for the maximum permissible weight of lift from knuckle to shoulder height(Texas Tech University, 1973-05) Dryden, Robert DwayneNot availableItem A psychophysical Study of Bi-Manual Lifting(Texas Tech University, 1982-12) Fox, Robert RNot Available.Item A psychophysical study of high-frequency lifting(Texas Tech University, 1993-08) Fox, Robert RErgonomic research on worker lifting in industry has most often concentrated on the maximum amount of weight that a worker is capable of and willing to lift in a given situation. However, in many industrial or service manual material handling situations the key question is not how much weight per lift a worker can handle but how frequently the worker is capable of lifting a light weight without strain or overexertion. Such situations often involve the intermittent handling of very light weights for relatively short periods of time. The overall objective of the study was to investigate subject physiological and psychophysical response to the standing arm lift of light weights. A psychophysical experiment with physiological data collection was designed to utilize two conditions of weight (1.5 lb and 10 lb) lifted from a shelf height of 30 inches to a shelf height of 50 inches (roughly knuckle-to-shoulder height). In this experiment the lift weights were given task variables and the frequency of lift was the dependent variable controlled by the subject. The subjects were instructed to work as hard as they could for a one-hour work session without overexerting themselves and called out adjustments (raise or lower) to a beeper-metronome which provided an audible signal to cue the subjects to lift. Heart rate and oxygen consultation data was collected during the last 15 minutes of the hour-long sessions. Two replications were performed for each weight. After the paced sessions were completed, each subject repeated one session for each of the weights with the same instructions only without the beeper-metronome to provide a cue. The subjects were instructed to maintain a steady pace, working as hard as they could, and relying only on their own internal impressions of pace to cue their lifts. The subjects were selected and classified according to body weight and somatotype or body-build. A nested-factorial analysis of variance was performed to evaluate the effects of body weight and lift weight on the chosen frequencies, heart rate, oxygen consumption and percentages of various aerobic capacities utilized. Correlation analysis was utilized to investigate the effects of somatotype on experimental performance. The mean frequencies of lift identified in the experiment were 31.21 lifts per minute and 23.50 lifts per minute for the 1.5 lb and 10 lb lift weights, respectively. Such frequencies of lift are much higher than lift frequencies studied as task variables in other psychophysical studies of lifting. The two weight conditions were significantly different from each other in their effects on subject metabolic energy expenditure with the subjects tending to work significantly harder physiologically at the heavier weight. Significant differences also existed between the subject body weight categories. There were no significant frequency or heart rate differences between the paced and unpaced experimental sessions. Somatotype was not shown to be a significant correlate of lift frequency in the 1.5 lb weight condition but appeared to be so in the 10 lb weight condition. Overall, the study provided insight into human psychophysical and physiological responses to the lifting of light weights. Furthermore, the study suggests guidelines for such work.Item An investigation of biomechanical, physiological and environmental heat stresses associated with manual lifting in hot environments(Texas Tech University, 1984-05) Hafez, Hala AdelNot availableItem Computerized dynamic biomechanical simulation of lifting versus inverse dynamics model: effects of task variables(Texas Tech University, 1995-12) Bernard, Tracey MarieAn examination of the kinetics and kinematics produced by the computerized dynamic biomechanical simulation model was performed to demonstrate the model's rehability in predicting stresses imposed on the body as a lifting task is performed. The peak kinetic parameters predicted by the simulation model were shown to be highly correlated, the kinematics less so, with the stresses imposed in actual lifts under different task conditions (range of lift, weight of load, size of box, and gender of lifter), thus its use can be advocated for lifting evaluations. Although highly correlated, the simulation tended to overestimate the values of the parameters. However, simple linear regression models provided in the analyses with R^2 values often m the range of 0.80 -0.95 can be used to correct for the prediction errors. The sensitivity analysis performed on inputs required to run the simulation model showed that the outputs of the model were consistent with the principles of biomechanics. The results provided in this study demonstrate that the simulation model should prove to be an effective alternative for the analysis of lifting tasks. By using the simulation model as a design tool, the tedious, time-consuming and costly data collection step required without use of a simulation tool can be eliminated and the ergonomist's time and effort spent more productively on design and evaluation.Item Design and evaluation of a mailbag for mailcarriers(Texas Tech University, 1984-05) Ashton, Nina ANot availableItem Determination of efficient methods of lift by comparing trained and untrained male and female lifters(Texas Tech University, 1978-12) Shannon, Richard HaroldNot availableItem Effect of psychosocial variables on maximum acceptable weight of lift(Texas Tech University, 1986-12) Selan, Joseph LThe objectives of this study were (l) to determine the effects of personality type in conjunction with social facilitation effects on the psychophysically-determined maximum acceptable weight of lift (MAWL), and 2) to establish guidelines for the psychophysical approach which control for the effects of psychosocial factors. To accomplish this, a laboratory study was conducted using 15 male subjects classified as Type A personalities (aggressive, impatient) and 15 Type B subjects (passive, patient). Following a training period, the subjects performed 5 psychophysical lifting tasks consisting of a floor to 30 inch lift using various frequencies of lift. (For the social facilitation manipulation, the subject lifted the box under 3 conditions: alone (box lowered automatically), with a confederate of similar physical ability lowering the box, and with a confederate of superior physical ability lowering the box^ The confederate conditions were introduced under the guise that the lowering apparatus was broken. Results indicated that Type A subjects worked at a higher percentage of their physical work capacity and selected heavier MAWLs than Type B subjects. Type A subjects required significantly less time deciding their MAWL, and made fewer weight adjustments in terms of decreasing box weight, than Type B subjects. Significant social facilitation effects were not obtained, nor was there a significant personality type x social condition interaction.Item Effect of task variable interactions in lifting and lowering(Texas Tech University, 1980-05) Mital, AnilNot availableItem Effects of fatigue on the kinematics of sagittal lifting(Texas Tech University, 1982-08) Lewis, RuthanNot availableItem Effects of running with backpack loads during simulated gravitational transitions: improvements in postural control(Texas Tech University, 2003-12) Brewer, Jeffrey DavidThe National Aeronautics and Space Administration is planning for long-duration manned missions to the Moon and Mars. For feasible long-duration space travel, improvements in exercise countermeasures are necessary to maintain cardiovascular fitness, bone mass throughout the body and the ability to perform coordinated movements in a constant gravitational environment that is six orders of magnitude higher than the "near weightlessness" condition experienced during transit to and/or orbit of the Moon, Mars, and Earth. This research provides insight for maintaining the ability of astronauts to perform coordinated, bipedal locomotion activities, following transitions between gravitational acceleration fields. In addition, a unique environmental simulator has been developed which enables further research regarding the complex interactions between humans and the environments in which they move. In order to investigate methods of improving postural control adaptation during these gravitational transitions, a treadmill based precision stepping task was developed to reveal changes in neuromuscular control of locomotion following both simulated partial gravity exposure and post-simulation exercise countermeasures designed to speed lower extremity impedance adjustment mechanisms. The exercise countermeasures included a short period of running with or without backpack loads immediately after partial gravity running. A novel suspension type partial gravity simulator incorporating spring balancers and a motor-driven treadmill was developed to facilitate body weight off-loading and various gait patterns in both simulated partial and full gravitational environments. Studies have provided evidence that suggests: (1) the environmental simulator constructed for this dissertation effort does induce locomotor adaptations following partial gravity running; (2) the precision stepping task is a sensitive test for illuminating aspects of these adaptations; and (3) musculoskeletal loading improves the locomotor adaptation process.Item Energy cost prediction models for manual lifting and lowering tasks(Texas Tech University, 1980-12) Asfour, Shihab SaadOne of the tasks that man is increasingly called upon to perform in modern industrial situations is manual materials handling. Despite the fact that industrial processes have become more automatic, still millions of tons of goods and materials are being handled and lifted manually. The need for manual materials handling may be dictated either by the type of the task performed or by the space available which does not permit the use of suitable mechanical devices. Lifting and lowering of loads manually are two typical activities of manual materials handling that are frequently encountered in most industries. One of the main features of most of the research work on manual lifting and lowering tasks is that it has been of a specific nature undertaken to answer particular limited questions. Much information has been acquired, but it has been acquired in a piecemeal fashion and as a result this area of research is a relatively uncharted area.Item Evaluation of anaerobic threshold for lifting tasks(Texas Tech University, 1983-12) Intaranont, KittiAn experiment was designed and conducted to accomplish the following objectives: 1. Comparison of the maximum V02 values, as measured during an arm cycling task, a bicycling task, and lifting activities, 2. Comparison of the anaerobic threshold (AT), as measured during an arm cycling task, a bicycling task, and lifting activities, 3. Development and testing of a mathematical model for the prediction of the lifting capacity using the criterion of an individual’s anaerobic threshold. A submaximal exercise protocol was applied to predict the aerobic capacity (V02 max or PWC). A graded exercise protocol using successive weight increments was applied to predict the AT. The dependent variables were the predicted maximum permissible (lbs.) of lift at 90% of the AT and the anaerobic threshold (1/min. of O2). The independent variables were task and individual variables. The task variables were ranges of lift (floor to knuckle height and knuckle to shoulder height) and frequencies of the lift (6, 7.5, and 9 lifts/min). The individual variables included body weight, lean body weight, and the PWC values predicted from bicycling and arm cycling. Ten make subjects, 10-27 years of age, participated in the experiment. The collection of physiological data began after a familiarization period. The results of the experiment were analyzed using the analysis of variance procedure. The predictive models were developed for each range of lift using a stepwise multiple linear regression technique. The models to predict lifting capacity of an individual were validated using three additional subjects. It was concluded that the models can reasonably predict lifting capacity based on the steady state of V02 and heart rate responses achieved during a 30 minute constant-load validation experiment. The predicted lifting capacity was also well within the 95th percentile of published lifting capacity norms. It was also concluded that the AT values were discretely related to the active muscle mass utilized in performing a physical task.Item Lifting capacity as a Function of Pperator and Task Variables.(Texas Tech University, 1974-08) Aghazadeh, FereydounNot Available.Item Lifting capacity determination as a function of task variables(Texas Tech University, 1983-08) Bakken, Gary MaynardNot availableItem Power as a predictor of lifting capacity(Texas Tech University, 1996-05) Dempsey, Patrick G.An experiment was conducted to examine the role that maximal lifting power has in predicting the maximum acceptable weight of lift (MAWL) for a frequency of one lift per 8 hours. The secondary aim of the study was to compare the ability of power to predict MAWL to previously used measures of capacity, including two measures of isometric strength, five measures of isokinetic strength, and isoinertial capacity on an isoinertial incremental lifting test. Twenty-five male subjects volunteered to participate in the experiment, and were examined by a physician prior to participation to ensure fimess for the experimental tasks. The experimental tasks were comprised of isometric, isokinetic, and isoinertial tests. The isometric tests involved maximum voluntary contractions for composite lifting tests at vertical heights of 15 and 75 cm. Peak isokinetic strength was measured at velocities of 0.1 m. • sec.'l, 0.2 m. • see."^ 0.4 m. • sec^, 0.6 m. • see."^ and 0.8 m. • sec."^ using a modified CYBEX II isokinetic dynamometer. Isoinertial lifting capacity was measured on the incremental lifting machine and peak power was measured on the incremental lifting machine by having subjects lift a 25 kg. load as quickly as possible. The results indicate that peak isoinertial power is significandy correlated with MAWL, and this correlation was higher than any of the correlations between the other predictor variables and MAWL. The relationships between the isokinetic strength measures and MAWL were stronger than the relationships between the isometric measures and MAWL. The magnitudes of the strength measures compared favorably with the values from previous studies. The mean MAWL value was shghtly lower than comparable values from databases in the hterature that are based on indusuial subject pools. The results provide indirect support for the hypothesis that lifting capacity and dynamic strength tests may be affected by the distribution of slow- and fast-twitch muscle fibers. Overall, the results suggest that tests used to predict MAWL should be dynamic rather than static. Suggestions for future research are presented which include repHcating the study with female subjects and an industrial subject pool.Item Prediction of acceptable lift capacity(Texas Tech University, 1972-12) McDaniel, Joe WileyNot availableItem Predictive models for the maximum acceptable weight of lift(Texas Tech University, 1974-08) Knipfer, Ronald EugeneNot available