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PubMed1986

Hormonal responses to a graded mental workload.

Three mental arithmetic tests of graded difficulty were presented to eight young male volunteers on consecutive days. The effort compensation patterns were investigated using urinary catecholamines and salivary cortisol. A significant increase in adrenaline excretion was found in response to all three tests. Urinary adrenaline was partially graded according to the level of difficulty of the tests. The response patterns to mental workload also included a significantly lower noradrenaline/adrenaline ratio and a higher adrenaline/dopamine ratio after the tests. No significant increase was found after the tests for noradrenaline and dopamine. Changes in salivary cortisol concentration during the tests were graded with respect to test difficulty between the easiest and both of the more difficult tests. Salivary cortisol concentration changes are proposed as the basis for field observations involving mental workload. It is concluded that mental workload causes distinguishable effort compensation patterns and that under certain conditions urinary adrenaline and salivary cortisol allow one to distinguish different mental workload levels.

Adult↗

PubMed1990

Driver workload during differing driving maneuvers.

Motorcycle-automobile accidents occur predominantly when the car driver turns left across the motorcyclist's right-of-way. Efforts to decrease this specific collision configuration, through an increase in motorcycle conspicuity, have concentrated on the physical characteristics of the motorcycle and its rider. The work reported here examines the behavior of car drivers during different driving sequences, in particular during left-turn maneuvers. An experiment is reported that used simultaneous video-taping of the driver and the forward-looking scene. Subjects followed a preset on-road course and were observed for head movements to determine the possibility of structural interference eye-blink frequency, probe-response time, and probe response error, as measures of cognitive or mental workload. In addition, the subjects completed two major subjective workload evaluations as reflections of effort directed to different components of the driving task. Results indicated that there were significant increases in head movements and mental workload during turn sequences compared to straight driving. This result of higher driver workload may be responsible for increasing the potential for detection failure. Such a propensity is also fostered by the higher structural interference that may be expected during turns. Failures to observe during turning sequences have differing outcomes depending on the presence of opposing traffic, as during the left turn, compared with the absence of such opposition, as occurs in the right turn. Also, the less conspicuous the oncoming vehicle in the left turn scenario, the higher the probability of detection failure. At the present time the least conspicuous powered vehicle is the motorcycle.

Accidents, Traffic↗

PubMed1990

Eye movement indices of mental workload.

Four investigations were carried out to assess the feasibility of using eye movement measures as indices of mental workload. In the first experiment, saccadic extent was measured during free viewing while subjects performed low, moderate and high complexity, auditory tone counting as the workload tasks. The range of saccadic extent decreased significantly as tone counting complexity (workload) was increased. In the second experiment the range of spontaneous saccades was measured under three levels of counting complexity with a visual task that did not require fixation or tracking. The results indicated that the extent of saccadic eye movements was significantly restricted as counting complexity increased. In the third experiment, the effects of practice were examined and decreased saccadic range under high tone counting complexity was observed even when significant increases in performance occurred with practice. Finally, in experiment 4, the first experiment was repeated with additional optokinetic stimulation and the saccadic range was again observed to decrease with tone counting complexity. The results indicated that the extent of spontaneous and elicited eye movements was significantly restricted as counting complexity increased. We conclude that this measure may provide a valuable index of mental workload.

Adult↗

PubMed1989

The effect of performance failure and task demand on the perception of mental workload.

An experiment was conducted to investigate the effects of incipient performance failure on subjective workload response. Unknown to the participants, there were two levels of demand embedded in the PC-based flight simulation performance task. These were included to assess whether task-naive subjects could distinguish variations in load in the face of repetitive performance failure. Results confirmed that participants were able to distinguish this change in load level under such circumstances and that failure resulted in higher perceived workload than did successful performance. Within these differences were significant effects dependent upon subject gender. In general, female participants performed more poorly and rated workload higher than their male counterparts. It is concluded that the experience of failure presents a significant source of workload in systems operation.

Journal Article↗

PubMed1993

Order effects and the weighting process in workload assessment.

Operators controlling a power grid were subjects in a mental workload experiment in which they performed their normal tasks under simulated quiet and busy conditions. Workload was assessed using the NASA Task-Load Index (TLX). It was found that there were significant differences between the two conditions, but there were no order effects. The value of the weighting procedure was assessed by correlating unweighted and weighted workload ratings. Although the correlations were high, they were not perfect, indicating some value for weighting the dimensions of the TLX. Large individual differences were observed in perceived workload.

Journal Article↗

PubMedDate not supplied

Intracerebral event-related potentials during memory workload.

The goals of this research were to use an original Memory Workload Paradigm with visually presented words and to explore the following points: (1) With depth electrodes, stereotaxically implanted in intracerebral structures bilaterally (amygdala, anterior hippocampus, posterior hippocampus, orbital-frontal, anterior cingulate gyrus and cortical areas) to delineate brain structures involved in this memory workload task. (2) To investigate whether a memory load effect can be demonstrated on the latencies and amplitudes of the late components of intracerebral event-related potentials (ERPs). (3) If a load effect is present, do intracerebral ERP latencies and amplitudes vary as a function of memory set size? The analysis of intracerebral ERPs revealed that a negative waveform with a maximum amplitude around 400 ms was the component which was significantly involved in memory workload tasks. Significant load effects for the N4 latency were found in both amygdalae and the left posterior hippocampus, as well as both anterior regions of the second temporal gyri (p < 0.01). The intracerebral N4 latency varied linearly as a function of set size while the amplitude varied quadratically for the right amygdala and the left posterior hippocampus (p < 0.05). The results support the conclusion that the Memory Workload Paradigm provides the possibility to use memory load effect on ERPs as a marker to identify which intracerebral structures are predominantly involved in memory functions.

Adult↗

PubMed1991

Workload and job satisfaction among general practitioners: a review of the literature.

The workload of general practitioners (GPs) is an important issue in health care systems with capitation payment for GPs services. This article reviews the literature on determinants and consequences of workload and job satisfaction of GPs. Determinants of workload are located on the demand side (list size and composition of the patient population) and the supply side (organization of the practice and personal characteristics of the GP). The effects of workload and job satisfaction on workstyle and quality of work have been reviewed. The length of consultations or booking intervals seems to be an important restriction for workstyle and quality of work.

Job Satisfaction↗

PubMed1995

Effects of attention and time-pressure on P300 subcomponents and implications for mental workload research.

Our approach to objective measures of mental workload is establishing relationships between components of the event-related brain potential (ERP) and information processing stages. These relationships can be used to infer the influence of specific workload conditions on specific processing stages. We recently showed that the ERP component P300 in choice tasks is composed of two subcomponents, P-SR and P-CR, which are time-related to stimulus-evaluation and response-selection. With these relations we could specify which processing stages were affected when certain workload conditions are varied. When attention was divided between the visual and auditory modalities compared to (unimodal) focused attention, the choice reaction time (RT) was prolonged, primarily in the auditory modality. This delay was mainly reflected in the P-CR latency, which shows that the division of attention mainly impairs the response-selection process in the auditory modality due to a bias of attention towards the visual modality. When the time-pressure was increased, the latency of the P-CR (and not of the P-SR) was shortened, but less than the choice RT. This suggests a (limited) acceleration of response-selection but not of stimulus evaluation. Since the response-selection process was accelerated less than the overt choice RT, an increase of the error rate was consequently observed. In summary we showed that increases of mental workload can induce accelerations or decelerations of specific processing stages which can be monitored by observing latency changes of the affiliated ERP components.

Adult↗

PubMed2005

Epidemiology and economic evaluation of severe sepsis in France: age, severity, infection site, and place of acquisition (community, hospital, or intensive care unit) as determinants of workload and cost.

PURPOSE: Severe sepsis is a leading cause of death in critically ill patients. We evaluated cost and workload according to infection site, place and time of acquisition, and severity. MATERIAL AND METHOD: We used a prospective 3-year database from 6 intensive care units (ICUs) including 1698 patients. RESULTS: Of the 1698 patients, 713 (42%) had severe sepsis at admission and 339 during the ICU stay (211 had both). Mortality was twice as high in patients with than those without ICU-acquired infection, independent of the presence of severe sepsis at admission. The mean (SD; median) cost of severe sepsis was 22 800 (21 400 ; 15 800 ). Among patients with severe sepsis at admission, workload and cost were higher for pneumonia, peritonitis, and multiple-site infections and for hospital-acquired (17,400 [14,700; 17,400]) vs community-acquired infection (12,600 [12,100 ; 8900 ]). Intensive care unit-acquired severe sepsis was associated with greater than 3-fold increases in workload and costs. By multiple linear regression, older age, emergency surgery, septic shock, Acute Physiological and Chronic Health Evaluation II score, and hospital or ICU-acquired severe sepsis were independently associated with higher costs. CONCLUSIONS: The wide variations in cost and workload invite efforts to identify patient subgroups most likely to benefit from high-cost treatments and from prevention, particularly targeting severe nosocomial infections.

APACHE↗

PubMed2006

The effect of crank rate on physiological responses and exercise efficiency using a range of submaximal workloads during arm crank ergometry.

This study examined the effects of variations in crank rate on physiological responses during submaximal arm ergometry. Fifteen non-specifically trained male subjects volunteered to participate in this study. Each subject undertook a discontinuous arm crank ergometry test (30, 50, 70, 90 W) on three separate occasions using crank rates of 50, 70, and 90 rev.min(-1). Respiratory parameters and heart rate were continuously monitored. An 80-microL capillary blood sample was obtained immediately following each exercise bout for the determination of whole blood lactate. Measures of efficiency were calculated using specific caloric equivalents of oxygen consumption (V(O2)). Heart rate was lowest (p < 0.05) at 30, 50, and 70 W using 50 rev.min(-1). Values of gross and net efficiency tended to be higher (p < 0.05) using 50 rev.min (-1) at the lower absolute workloads, but no differences (p > 0.05) were observed between the three crank rates at 90 W. No differences (p > 0.05) were observed between crank rates for delta efficiency. This study confirms that variations in crank rate can influence gross and net values of V(O2) and exercise efficiency at low absolute workloads, but crank rate ceases to be an influential factor at moderate workloads. Further research is required to identify the specific mechanisms underpinning the observations reported in the present study relating to the interaction between crank rate, workload, and exercise efficiency during arm crank ergometry.

Adult↗

PubMed2000

On-line driver workload estimation. Effects of road situation and age on secondary task measures.

In order to develop a driver-car interface that adapts the presentation of messages generated by in-vehicle information systems to driver workload, two experiments investigated potential determinants of driver visual and mental workload as indicated by performance on two secondary tasks. Experiment 1 suggested that road situation is a major determinant of visual and mental workload of the driver and that the processing resources of older drivers are somewhat more limited than those of younger and middle-aged drivers. Familiarity with the area of driving (when guided) and time of day (associated with traffic density) showed no secondary task effects. Experiment 2 showed that the categorization of road situations, proposed in Experiment 1, could underlie adaptation of visually loading messages to the workload incurred by driving. This was not found with respect to mentally loading messages.

Adult↗

PubMed1990

Maximum acceptable repetitive lifting workload by Chinese subjects.

This study used psychophysical methods to determine the acceptable mean maximum lifting workload for eight Chinese young male subjects, and examined the effects of lifting technique (including freestyle, stoop and squat), lifting frequency (including 2, 3, 4, 5 and 6 lifts/min) and physical characteristics on the maximum acceptable workload. The results are described as follows: (1) The maximum acceptable weights selected by subjects varied from 11.34 to 18.33 kg with changes in lifting technique and frequency. These data were lower than those previously obtained; (2) The upper limit of physiological tolerance over an 8 h workday was also generally lower than previously suggested. However, this upper limit varied with changes in lifting technique and frequency, and in some circumstances it was the same as or even higher than previous limit; (3) Lifting efficiency was affected significantly by technique and frequency. The rank order of efficiency for three lifting techniques were freestyle, stoop and squat. Efficiency was greatest when lifting frequency was between 5 and 6 lifts/min; and (4) The correlations between the maximum acceptable workloads selected by subjects and anthropometric sizes were significant, but those between maximum acceptable workload and isometric strength were not.

Adult↗

PubMed1999

The influence of aircraft proximity data on the subjective mental workload of controllers in the air traffic control task.

This paper outlines an investigation of the impact of aircraft proximity and relationship data on the subjective mental workload of air traffic controllers. Aircraft relationships were categorized into one of 81 different categories, and these relationships were then used to predict subjective mental workload values (as reported by the participants). The results indicated that this methodology could predict subjective mental workload to an accuracy of 73%, with post-hoc analysis improving this prediction rate to 93%. These results are discussed with respect to their contribution to an understanding of the drivers of mental workload in Air Traffic Control.

Adult↗

PubMed1989

Workload, stress, and strain among police officers.

Data relevant to stress and strain were analyzed separately for police officers with high and low workloads. Although these groups of officers were not found to differ in demographic characteristics or on overall levels of stress and strain, the sources of stress and strain were remarkably different. For the low workload officer, the sources of stress and strain appear to be difficulties in interpersonal relations with peers, community, and especially with supervisors. These difficulties appear to be mediated by effects on self-evaluation. The sources of stress and strain among high workload officers appear to be stress-producing events in their lives in general, as well as in performing the job of patrol officer and in dealing with crime and related matters. The differences between high and low workload officers can be explained by social comparison theory, by identity theory, or by Selye's stress theory.

Achievement↗

PubMed1980

Workload recording by microcomputer.

Workload recording as designed by the College of American Pathologists has proven to be an invaluable aid in the assessment of overall laboratory operation. The administrative information derived from the compilation of these workload statistics is utilized to provide effective and these workload statistics is utilized to provide effective and efficient laboratory management. A microcomputer-based system for the pathology department that permits the accumulation of daily raw workoad data is descirbed. A monthly cummulative summary report is subsequently produced, complete with computer-derived College of American Pathologists workload units.

Computers↗

PubMed2004

A combined fuzzy-neural network model for non-linear prediction of 3-D rendering workload in grid computing.

Implementation of a commercial application to a grid infrastructure introduces new challenges in managing the quality-of-service (QoS) requirements, most stem from the fact that negotiation on QoS between the user and the service provider should strictly be satisfied. An interesting commercial application with a wide impact on a variety of fields, which can benefit from the computational grid technologies, is three-dimensional (3-D) rendering. In order to implement, however, 3-D rendering to a grid infrastructure, we should develop appropriate scheduling and resource allocation mechanisms so that the negotiated (QoS) requirements are met. Efficient scheduling schemes require modeling and prediction of rendering workload. In this paper workload prediction is addressed based on a combined fuzzy classification and neural network model. Initially, appropriate descriptors are extracted to represent the synthetic world. The descriptors are obtained by parsing RIB formatted files, which provides a general structure for describing computer-generated images. Fuzzy classification is used for organizing rendering descriptor so that a reliable representation is accomplished which increases the prediction accuracy. Neural network performs workload prediction by modeling the nonlinear input-output relationship between rendering descriptors and the respective computational complexity. To increase prediction accuracy, a constructive algorithm is adopted in this paper to train the neural network so that network weights and size are simultaneously estimated. Then, a grid scheduler scheme is proposed to estimate the queuing order that the tasks should be executed and the most appopriate processor assignment so that the demanded QoS are satisfied as much as possible. A fair scheduling policy is considered as the most appropriate. Experimental results on a real grid infrastructure are presented to illustrate the efficiency of the proposed workload prediction--scheduling algorithm compared to other approaches presented in the literature.

Journal Article↗

PubMed1995

Relationship between heart rate and oxygen kinetics during constant workload exercise.

BACKGROUND: Oxygen uptake during constant workload exercise increases exponentially from its resting value before reaching a steady state. The difference between the actual rate of oxygen consumption at the onset of exercise and the steady state is an oxygen deficit. Similarly, the normal sinus node increases its rate at the onset of exercise before achieving a steady state, thereby producing a heart rate deficit. The purpose of this study was to test the hypothesis that elimination of the heart rate deficit by an instantaneous increase in heart rate at the onset of constant workload exercise to the steady-state level would reduce the oxygen deficit and improve the perceived difficulty of exertion as compared with the chronotropic response of the normal sinus node. METHODS AND RESULTS: Ten subjects with normal sinus node function who had DDD pacemakers implanted for AV block completed a symptom-limited maximal treadmill exercise test using the Chronotropic Assessment Exercise Protocol (CAEP) to assess sinus node function, maximal heart rate, and VO2max. The subjects then performed constant workload exercise tests (6-min duration) at a workload equal to approximately 50% of metabolic reserve with the pacemaker randomly programmed to each of three patterns of chronotropic response: (1) DDD (lower rate 60 beats/min); (2) Fast (lower rate abruptly programmed to the expected value at 50% metabolic reserve); and (3) Overpaced (lower rate at least 80% of the age predicted maximum). The oxygen deficit was lower with the fast chronotropic response (434 +/- 238 mL O2) than with either the DDD (512 +/- 233; P = 0.02), or overpaced chronotropic patterns (488 +/- 238; P = 0.02 vs fast). The rate constant for change in VO2 was highest with the fast chronotropic pattern (2.85 +/- 1.38) compared with either the DDD (2.25 +/- 0.64; P = 0.01) or overpaced (2.38 +/- 0.43; P = 0.02) patterns. The Borg perceived exertion rating was lowest with the fast chronotropic response (P = 0.02 vs DDD and P = 0.02 vs overpaced). CONCLUSIONS: The results of this study suggest that oxygen kinetics and exertional symptoms are improved by an abrupt increase in pacing rate at the onset of exercise to a value that is appropriate for metabolic demand as compared with the DDD pacing mode in patients with normal sinus node function. In contrast, an overly aggressive chronotropic response was not associated with improved oxygen kinetics or exertional symptoms.

Adult↗

PubMed1990

Out of hours workload of a suburban general practice: deprivation or expectation.

The out of hours workload of a training practice in a suburban and semirural area on the south coast of England was studied for one year. An overall rate of contact of 273/1000 patients was found, which indicated a workload greater than that reported in most other studies. The duty doctor received over 35 telephone calls from patients during some Saturdays (1200 Saturday to 0800 Sunday) and Sundays (0800 to 0800 Monday), up to five being between 2300 and 0700. Of the patients who contacted a general practitioner, 44% were given advice by telephone and 4.9% were admitted to hospital. The admission rate was lower than that given in other studies. A considerable proportion of the workload arose from doctors covering the casualty department of a cottage hospital. Patients having a high expectation of 24 hour care by general practitioners in an area of comparative affluence (Jarman indices -13.8 to 1.7) may account for this aspect of the workload.

England↗