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PubMed2005

EEG and ECG changes during simulator operation reflect mental workload and vigilance.

BACKGROUND: Performing mission tasks in a simulator influences many neurophysiological measures. Quantitative assessments of electroencephalography (EEG) and electrocardiography (ECG) have made it possible to develop indicators of mental workload and to estimate relative physiological responses to cognitive requirements. OBJECTIVE: To evaluate the effects of mental workload without actual physical risk, we studied the cortical and cardiovascular changes that occurred during simulated flight. METHODS: There were 12 pilots (8 novices and 4 experts) who simulated a flight composed of 10 sequences that induced several different mental workload levels. EEG was recorded at 12 electrode sites during rest and flight sequences; ECG activity was also recorded. Subjective tests were used to evaluate anxiety and vigilance levels. RESULTS: Theta band activity was lower during the two simulated flight rest sequences than during visual and instrument flight sequences at central, parietal, and occipital sites (p < 0.05). On the other hand, rest sequences resulted in higher beta (at the C4 site; p < 0.05) and gamma (at the central, parietal, and occipital sites; p < 0.05) power than active segments. The mean heart rate (HR) was not significantly different during any simulated flight sequence, but HR was lower for expert subjects than for novices. The subjective tests revealed no significant anxiety and high values for vigilance levels before and during flight. CONCLUSIONS: The different flight sequences performed on the simulator resulted in electrophysiological changes that expressed variations in mental workload. These results corroborate those found during study of real flights, particularly during sequences requiring the heaviest mental workload.

Aerospace Medicine↗
PubMed1995

'Unseen' on-call workload of a general surgical team.

Over a four-month period, we assessed the contribution made to the on-call workload of a general surgical team, by referrals and assessments of patients who had not been admitted under surgical care and were therefore not recorded in current audits of general surgical activity--the 'unseen workload'. Up to 5 1/2 hours per day on-call (mean 101 minutes) was spent assessing these referrals. There was a mean number of 3.6 referrals (range 1 to 7). Although 51 percent of these referrals were deemed to be non-surgical after assessment, the majority (77 percent) were believed to be appropriate. The Accident & Emergency Department referred 46 per cent of patients with only 7 percent requiring surgical management. This study shows that while hours of work are important in assessing the workload of a junior doctor on-call, the intensity of the workload is just as important in determining the impact on staff. There is a greater workload than revealed by audit of just surgical admissions and operations alone.

General Surgery↗
PubMed2006

The evaluation of smaller plasterboards on productivity, work demands and workload in construction workers.

Manual handling of plasterboards in order to construct interior building walls is a risk factor for musculoskeletal complaints. Unfortunately, mechanical lifting aids to reduce the physical workload are impractical for this task. Therefore, the effect of smaller plasterboards on productivity, work demands and workload was evaluated in an exploratory study among experienced construction workers (n=4-8) at the worksite. The dimensions and weight of the conventional and smaller plasterboards (PB) were: PB120 (2440 x 1200 x 15 mm; 33 kg) and PB90 (2440 x 900 x 12.5 mm; 20 kg), respectively. Productivity was defined as meters of plasterboard mounted. Work demands were assessed by means of real time observations of tasks and activities. Workload was determined using continuous heart rate monitoring and subjective judgments of perceived workload. Productivity and total work time per working day did not differ between PB120 and PB90. Duration of mounting (29% increase) and anchoring (26% increase) were longer for PB90 than PB120. Duration of lifting, carrying and turning over plasterboards, and percentage of heart rate reserve showed no difference between PB120 and PB90. A majority of the workers preferred PB90. For the last two reasons and because PB90 weighs approximately 40% less than PB120, PB90 seems preferable. The workload in both conditions, however, was considered high.

Construction Materials↗
PubMed2005

Proportionality of rate response to metabolic workload provided by a rate adaptive pacemaker with automatic rate profile optimization.

OBJECTIVE: The rate response of a pacemaker (PM) was compared with the sinus rate in patients during repeated exercise tests, at different settings of the rate response parameters. METHODS AND RESULTS: In patients with paroxysmal sick sinus syndrome (n=3) or atrioventricular block (n=8), a rate responsive PM was implanted. The activity-dependent pacing rate is represented by the sensor indicated rate (SIR). Each patient performed a treadmill test at 1 month, 1 year, and 2 years after implantation. Prior to the 1 and 2 year tests PM parameters were changed to produce a larger rate increase, especially at moderate levels of daily life activity. During the tests the O(2) consumption and CO(2) production were measured, breath-by-breath, to determine the workload and the anaerobic threshold. On average the workload (oxygen consumption), the patient's sinus rate, and the SIR, showed a linear increase with the workload imposed by the treadmill. In the 1 month and 1 year test the SIR was much lower than the spontaneous rhythm, especially at low or moderate workloads. On the more dynamic setting of several rate adaptive parameters at 2 years, the SIR changed significantly and was close to the spontaneous HR. CONCLUSIONS: The examined PM provides a paced heart rate that is proportional to the workload. For the first time the effect of reprogramming rate response parameters to produce an SIR that is similar to the sinus rate is shown in this study.

Aged↗
PubMed2005

Influence of calcium-induced workload transitions and fatty acid supply on myocardial substrate selection.

Because of differences in energy yield and oxygen demand, the selection of oxidative fuels is important in the hypoxic or ischemic heart muscle. The aim of the present study was to clarify the contradictions observed in the effects of workload and fatty acid supply on myocardial fuel preference in isolated perfused rat hearts. Nuclear magnetic resonance spectroscopy combined with the administration of substrates labeled with the stable isotope carbon 13 and isotopomer analysis of glutamate labeling offers an opportunity to simultaneously measure metabolic fluxes in pathways feeding into the tricarboxylic acid (TCA) cycle. The work output was modulated by changes in extracellular calcium. In the presence of 5 mmol/L glucose, 0.5 mmol/L octanoate in the perfusate dominated the oxidative metabolism, and workload had little effect on the ratio of glucose to fatty acid utilization. This was the case even when the octanoate concentration was lowered to 50 micromol/L. The relative rate of replenishment of the TCA cycle intermediates was higher at a low workload. The redox state of flavoproteins in the intact heart was monitored fluorometrically to obtain an estimate of the mitochondrial reduced/oxidized nicotinamide-adenine dinucleotide ratio (NADH/NAD ratio) for assessment of the dominant level of regulation of cell respiration, and the myoglobin spectrum was simultaneously monitored to evaluate the oxygenation status of the myocardium. Commencement of octanoate infusion (50 micromol/L or 0.5 mmol/L) caused a large but transient reduction of mitochondrial NAD and, conversely, its cessation elicited NADH oxidation and rebound reduction. During glucose oxidation, an increase in workload led to oxidation of the mitochondrial NADH, but this effect was much smaller in the presence of 50 micromol/L octanoate and absent in the presence of 0.5 mmol/L. This indicates that strong control of oxygen consumption during glucose oxidation is exerted in the mitochondrial respiratory chain, whereas equal control during fatty acid oxidation is exerted within the metabolic pathway upstream from the respiratory chain. It is concluded that when a medium-chain fatty acid is available, myocardial workload and energy consumption have little influence on fuel preference and glucose oxidation remains suppressed.

Animals↗
PubMed1999

Workload, capacity for coping and psychological and physical outcomes amongst home helps in the Netherlands.

Owing to many developments and changes in home care in the Netherlands, a national study was carried out. One of the aims was to examine the differences between the six categories of home help in the Netherlands regarding workload, pressure of work and capacity for coping. A total of 474 home helps from six categories participated in the study. A structured questionnaire, based on the components of the research model, was used, which consisted of existing scales regarding workload (organizational and job characteristics, working conditions), psychological and physical outcomes (job satisfaction, burnout, health) and capacity for coping (social support, leadership style, coping strategies). Workload, specifically organizational and job characteristics are scored low by alpha helps and, to a lesser degree, by A home helps. The higher categories of home help experienced relatively bad working conditions. Home helps, except for alpha helps, are, on the whole, quite satisfied with their work, which is one of the psychological and physical outcomes. The higher categories of home help (C, D and E carers) experienced high feelings of emotional exhaustion. Health, absenteeism and back problems did not differ significantly amongst home helps. When looking at capacity for coping, traditional home helps (A to E) received more social support. The subordinate categories of home help dealt less actively with their problems and sought less social support than the other categories. Alpha helps are not employed by the organization and this might cause low organizational and job characteristics, and little social support. Their satisfaction scores suggest that they would like to see their low organizational involvement changed. The higher categories of home help, who carry out many psychosocial tasks, have higher emotional and mental workload and high burnout scores. B, C and D carers, who perform personal care and have to adhere to strict planning, experience extreme time pressure and a high physical workload.

Journal Article↗
PubMed1991

Aerobic and anaerobic energy contribution during maximal work output in 90 s determined with various ergocycle workloads.

The aim of this experiment was to evaluate the effect of different workloads on the relative contribution of the various energy delivery systems during a 90-s ergocycle test. Nine male subjects, 22 +/- 1 (mean +/- SD) years of age and weighing 71.4 +/- 6.8 kg, were submitted to a VO2max test, as 10-s test (0.1 kp/kg) and three 90-s tests at different loads (LO: 0.05, ME: 0.075 and HI: 0.1 kp/kg) on an ergocycle. No difference was found between peak power output during the 10-s and HI tests. No differences were observed in the total work output performed during 90 s at different workloads (between 481 and 495 J/kg) as well as in the contribution of aerobic and anaerobic pathways to total energy production. However, VO2max was reached earlier during the ME and HI tests than during the LO test. These results indicate that variation in workload did not influence the total work output and the total contribution of aerobic and anaerobic systems during maximal 90-s ergocycle performances. However, variation in workload had an impact on the relative aerobic and anaerobic contribution at various time points. It is concluded that a 90-s ergocycle test with a resistance of at least 0.1 kp/kg is required to appropriately assess maximal anaerobic power while anaerobic capacity might be measured with workloads as low as 0.05 kp/kg.

Adult↗
PubMed2002

Prognostic impact of workload in patients with congestive heart failure.

AIMS: Recent data underline the prognostic value of cardiopulmonary exercise parameters (eg, peak oxygen consumption [PVO2]), percentage of predicted oxygen consumption [ppVO2], ventilation, and workload) in patients with congestive heart failure. These parameters were not yet compared in a multivariate analysis. METHODS AND RESULTS: To detect the superiority of one of these parameters, in a prospective 1-year follow-up study we investigated 226 patients with heart failure. The end point of the study was combined death and prioritization for urgent cardiac transplantation within 1 year. Cardiopulmonary exercise testing was performed with evaluation of peak oxygen consumption, percentage of predicted peak oxygen consumption, peak carbon dioxide production, ventilation, workload, anaerobic threshold, and ventilation/carbon dioxide production ratio. All variables were univariate predictors of 1-year mortality and urgent transplantation. Multivariate analysis demonstrated that only workload and ventilation were independently related to 1-year mortality and urgent cardiac transplantation, whereas peak oxygen consumption or percentage of predicted peak oxygen consumption did not reach statistical significance in this model. CONCLUSION: Workload on bicycle stress test correlates to 1-year mortality. More important, workload is a more powerful predictor of 1-year survival compared with established markers such as pVO2 or ppVO2.

Anaerobic Threshold↗
PubMed2004

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 2. Measurement error and effect of training stage on the relationship between objective and subjective criteria of training workload.

AIM: To identify the magnitude and sources of error involved in simply quantifying the workload of a group of Thoroughbred racehorses in training. METHODS: Data were obtained from seven 2-year-old fillies trained for 13 weeks on sand and grass tracks at various cantering velocities, and at the gallop in the last 4 weeks. Four fillies completed training and comprised a 'high exercise intensity' subgroup; three fillies did not complete all gallops due to lameness or injury and comprised a 'medium exercise intensity' subgroup. The trainer recorded the distance, time, track used, and subjective gait (SG; viz canter, 1/4-pace, 1/2-pace and gallop) of each horse each day. Data were analysed to describe the training programme and sources of variation in workload. A cumulative workload index (CWI) was devised to simply express distance and velocity aspects of the training programme. RESULTS: The magnitude of errors in measurement of timing and distance were small but significant (<0.8%, p=0.01). SG was an inaccurate descriptor of velocity. Mean velocity of 1/2-pace decreased from 8.92 (SE 0.049) in Weeks 6-8 to 6.33 (SE 0.061) m/sec after the start of galloping sessions in Week 9 (p=0.01). Track surface had a significant effect on the velocity of 1/2-pace (p=0.001). The fastest velocity was recorded on the grass (9.06, SE 0.292 m/sec), followed by 'plough' (8.23, SE 0.152 m/sec), and sand (7.90, SE 0.132 m/sec) tracks. The CWI of the horses ranged between 1,085,000 and 1,634,000 (mean=1,428,000; SE 78,000). The average exercise intensity per week was 110,000 (SE 1,048). There were no significant differences between high and medium exercise intensity subgroups for the canter and 1/4-pace. The high exercise subgroup had a greater CWI for the 1/2-pace (839,000 vs 559,000; p=0.004), gallop (71,000 vs 31,000; p=0.001), and total index (1,580,000 vs 1,242,000; p=0.001). CONCLUSIONS: The workload history of a horse can be accurately described using an index based on manual measurement of the time and distance worked. CLINICAL RELEVANCE: Accurate and precise data on the training programme of performance horses are likely to enable greater differentiation of aspects of workload which are associated with both performance and injury.

Journal Article↗
PubMed1983

Assessment of technologist workload as a factor in quality of laboratory performance.

A very significant effort in terms of dollars and man hours (up to 40% of workload) is spent on providing effective quality control in the chemistry laboratory. An important factor in quality of performance which is intuitively obvious but not readily quantitated is technologist workload. We have been able to significantly correlate (P less than 0.01) over a period of 4 years, performance in an external proficiency survey with technologist workload. Not surprisingly, the data suggests that the quality of test results diminishes as workload increases. The management strategy should then be directed towards decreasing workload possibly through appropriate automation.

Automation↗
PubMed1981

Control of cardiac output in exercising dogs using different types of workload.

The system which controls cardiac output was studied in dogs during exercise on the treadmill. The aim was to investigate whether the pattern of the workload influences the control system. To measure cardiac output, electromagnetic flow probes were implanted at least 10 days before the exercise study. During the experiments cardiac output was computed on a beat-to-beat basis. We compared changes in cardiac output resulting from stepwise, sinusoidally and randomly varying workloads, obtained by changing treadmill velocity accordingly. The time constants found with sinusoidally and randomly varying workloads were 11.6 and 10.0s respectively. The time constants of the alteration in cardiac output resulting from a step function was 9.9s for the positive step and 15.6s for the negative step. However when the stepwise change in workload was between a velocity of 0.67 and 1.56 m.s-1 positive and negative steps yielded the same time constant (13.5 s). It is concluded that the pattern of the workload has no influence on the control system of cardiac output during exercise.

Animals↗
PubMed2004

Limited transfer of cytosolic NADH into mitochondria at high cardiac workload.

Glycolysis supplements energy synthesis at high cardiac workloads, producing not only ATP but also cytosolic NADH and pyruvate for oxidative ATP synthesis. Despite adequate Po(2), speculation exists that not all cytosolic NADH is oxidized by the mitochondria, leading to lactate production. In this study, we elucidate the mechanism for limited cytosolic NADH oxidation and increased lactate production at high workload despite adequate myocardial blood flow and oxygenation. Reducing equivalents from glycolysis enter mitochondria via exchange of mitochondrial alpha-ketoglutarate (alpha-KG) for cytosolic malate. This exchange was monitored at baseline and at high workloads by comparing (13)C enrichment between the products of alpha-KG oxidation (succinate) and alpha-KG efflux from mitochondria (glutamate). Under general anesthesia, a left thoracotomy was performed on 14 dogs and [2-(13)C]acetate was infused into the left anterior descending artery for 40 min. The rate-pressure product was 9,035 +/- 1,972 and 21,659 +/- 5,266 mmHg.beats.min(-1) (n = 7) at baseline (n = 7) and with dobutamine, respectively. (13)C enrichment of succinate was 57 +/- 10% at baseline and 45 +/- 13% at elevated workload (not significant), confirming oxidation of [2-(13)C]acetate. However, cytosolic glutamate enrichment, a marker of cytosolic NADH transfer to mitochondria, was dramatically reduced at high cardiac workload (11 +/- 1%) vs. baseline (50 +/- 14%, P < 0.05). This reduced exchange of (13)C from alpha-KG to cytosolic glutamate at high work indicates reduced shuttling of cytosolic reducing equivalents into the mitochondria. Myocardial tissue lactate increased 78%, countering this reduced oxidation of cytosolic NADH. The findings elucidate a contributing mechanism to glycolysis outpacing glucose oxidation in the absence of myocardial ischemia.

Acetates↗
PubMed2000

Ventilatory response to incremental and constant-workload exercise in the presence of a thoracic restriction.

In the presence of an externally applied thoracic restriction, conflicting ventilatory responses to exercise have been reported, which could be accounted for by differences in exercise protocol. Seven male subjects performed two incremental and two constant-workload ergometer tests either unrestricted or in the presence of an inelastic corset. Ventilatory variables and arterial estimates of PCO(2) were obtained breath by breath. Subjects hyperventilated in the presence of restriction during the constant-workload test (38.4 +/- 3.0 vs. 32.8 +/- 3.0 l/min for the average of the last 3 min of exercise, P < 0.05), whereas, at an equivalent workload during the incremental test, ventilation was similar to unrestricted values (unrestricted = 26.3 +/- 1.6 vs. restricted = 27.9 +/- 2.3 l/min, P = 0.36). We used a first-order linear model to describe the effects of change in workload on minute ventilation (24). When the time constants and minute ventilation values measured during unrestricted and restricted constant-workload exercise were used to predict the ventilatory response to the respective incremental exercise tests, no significant difference was observed. This suggests that hyperventilation is not seen in the restricted incremental test because the temporal dynamics of the ventilatory response are altered.

Adult↗
PubMed1998

Increased workload enhances force output during pedaling exercise in persons with poststroke hemiplegia.

BACKGROUND AND PURPOSE: A principle of poststroke rehabilitation is that effort should be avoided since it leads to increased spasticity and produces widespread associated abnormal reactions. Although weakness also contributes to movement dysfunction after a stroke, it has been feared that heightened activity levels during strength training will further exacerbate the abnormal tone imbalance present in spastic hemiplegia. The purpose of this study was to test this hypothesis by quantifying the effects of increased workload on motor performance during different speeds of pedaling exercise in persons with poststroke hemiplegia. METHODS: Twelve healthy elderly subjects and 15 subjects with poststroke hemiplegia of greater than 6 months since onset were tested. The experimental protocol consisted of having subjects pedal at 12 randomly ordered workload and cadence combinations (45-J, 90-J, 135-J, and 180-J workloads at 25, 40, and 55 rpm). Pedal reaction forces were measured and used to calculate work done by each leg, including net positive and negative components. An electromyogram was recorded from seven leg muscles. RESULTS: The main finding was that net mechanical work done by the plegic leg increased as workload increased in 75 of 81 instances without increasing the percentage of inappropriate muscle activity. CONCLUSIONS: This study provides evidence that persons with hemiplegia increase force output by their plegic limb when pedaling against higher workloads without exacerbation of impaired motor control. Therefore, exertional pedaling exercise is a beneficial intervention for achieving gains in muscular force output without worsening motor control impairments.

Aged↗
PubMed1996

Effects of chicken extract on the recovery from fatigue caused by mental workload.

Folk wisdom suggests that chicken extract is useful for recovery from physical and mental fatigue. To explore this question, the physiological effect of Brand's Essence of Chicken (BEC), a popular chicken extract used as a traditional remedy, was assessed during recovering from mental stress. We quantitated the blood levels of stress-related substances, and examined the task performance and subjects' mood states during mental workloads. Subjects were 20, healthy male students who have never tasted BEC. They took two bottles of BEC or a placebo (70 ml/bottle) daily in the morning for 7 days. On the final experimental day, two mental workload tests were performed: (A) a mental arithmetic test (MAT; 1600 trials of two or three figure-addition or subtraction for 40 min). (B) a short-term memory test (SMT; 20 trials of memorizing 9 digit numbers). Blood was collected before and after each workload task. After the mental workload, the recovery of mean cortisol level of subjects who consumed BEC was significantly faster than that for those consuming the placebo. The task performance of subjects performing the MAT and SMT was also improved with BEC consumption compared with placebo. According to the profile of mood state questionnaire, subjects felt more active and less fatigued during the workload when they took BEC regularly. We conclude that the extract of chicken has the potential to metabolize stress-related substance in blood and to promote recovery from mental fatigue.

Adolescent↗
PubMed2003

[A workload analysis of a visiting nursing service based on a health center in Seoul].

PURPOSE: This study focused on analysing the workload of visiting nurses based on a health center. METHOD: A Prospective descriptive analysis of self-records for workload data from 115 visiting nurses during 4 weeks was done. In addition, a cross-sectional analysis of linked data to grasp the priority of visiting nursing services from 155 visiting nurses at the 25 health centers in Seoul. RESULT: Time allocation that was performed on all nursing workload of visiting nurses was identified as follows: First, the inside workload of the health center took up 60% of all visiting nurse activities. Second, providing direct nursing care(caseload) took up 25%. Third, outside nursing activities excluding the caseload provided in the health center took up 15% of all working time. Fourth, the core works to have a high priority among visiting nursing activities were family health assessment, planning and evaluation of a visiting nursing program, personal health assessment, and so forth. CONCLUSION: The workload of a visiting nurse suggests that the caseload of visiting nurses in a health center needs to be increased. Also, our results will contribute to baseline data used to establish a proper visiting nurses infrastructure based on the demand of visiting nursing services.

English Abstract↗
PubMed1990

Workload measurement in long term care pharmacy.

This paper describes the implementation of the Canadian Hospital Pharmacy Workload Measurement System (CHPWMS) by the pharmacy department of a 475-bed long term care facility. The CHPWMS description of a computerized individual patient prescription service provided the basis for the implementation. Following an initial appraisal of similarities between chronic care pharmacy services and the services outlined by CHPWMS, a program was developed and evaluated with the assistance of a pharmacist consultant. During a four-month trial all measurable work was recorded in a process that separated reportable (CHPWMS-defined) activities from other work activities. Eighty percent of the department's workload was accountable as reportable units using standard times. Nonreportable workload was documented using actual times, and adapted standard times. Dispensing accounted for the largest proportion of workload (79%). Manufacturing was the most frequently performed nonreportable activity. Pharmacist workload supported the desired level of 50% nondispensing activities. The productivity index of available worked hours was 70%. The consistent pattern of the recording suggested staff commitment. The program has been used to justify and monitor staffing levels.

Documentation↗
PubMed1992

Women's workload and its impact on their health and nutritional status.

This paper highlights various issues in relation to the workload of women in developing countries and its impact on health and nutritional status. The determining factors in women's workload and work-time and the methods employed for assessment are described. The drawbacks of the methods used and the resulting inconsistencies in the data are reviewed. How women are subjected to different health stresses owing to their productive and reproductive roles has been examined under three categories of work: economic, domestic and agricultural. The interaction of women's workload and health is complex and multifactorial owing to variations in the environment and socio-economic conditions within developing countries. There is a critical need to re-examine the assumptions existing about women's workload in programmes aimed at reducing work-time and workload of women in developing countries.

Developing Countries↗