Equal Workloads Research Articles

Physiological responses to repeated heat exposure under equal work load conditions

Objectives. This study aimed to verify the responses of skin temperature, oxygen saturation, blood pressure, rate pressure product (RPP), heart rate (HR) and HR variability after continuous and intermittent exposure to heat from a fire, keeping the work load equal between the conditions. Methods. Sixteen men from a fire department were subjected to two experimental conditions: continuous exposure to the heat from a fire for 30 uninterrupted minutes (1 × 30 min); and intermittent exposure to the heat of the fire organized by two 15-min re-entries of exposure to the heat interspersed with 10 min of non-exposure (2 × 15 min). Results. The main finding was lower percentage changes in HR (+1.7% vs +38% vs +26%), mean normal interval (−0.97% vs −26% vs −20%), RMSSD (−5.0% vs −62% vs −48%) and RPP (+0.79% vs +38% vs 34%) in re-exposure (15–30 min) when compared for 0–30 min and 0–15 min, respectively. Conclusion. Under equal workloads, intermittent exposure to heat is an efficient strategy for fire suppression activities. In addition to skin temperature and HR, RPP constitutes another variable to monitor firefighter health between re-entries, as it is easy to administer, inexpensive and reflects cardiac overload.

Determinants of Workplace Bullying Types and Their Relationship With Depression Among Female Nurses.

Workplace bullying is commonly experienced by nurses worldwide. This study was conducted to examine the determinants of different types of workplace bullying and their relationship to depression in female nurses. A cross-sectional correlational study was employed, and 484 female nurses from a large medical center in southern Taiwan completed the questionnaire. Data were analyzed using logistic regression analysis. Being unmarried and working in medical/surgical units were found to be the major determinants of work-related bullying, whereas being unmarried was found to be the single determinant of person-related and physical-intimidation bullying. Moreover, work-related and person-related bullying were both found to be significant determinants of depression. Nursing administrators should establish workplace-bullying prevention and management strategies by setting reasonable and equal workloads for nurses, assigning tasks equitably, and building depression-related support and consultation groups.

A novel optimization approach for segmented rabbit chase oriented U-type assembly line design: an application from lighting industry

PurposeRabbit chase (RC) is used as one of the most effective techniques in manufacturing systems, as such systems have high level of adaptability and increased productivity in addition to providing uniform workload balancing and skill improving environment. In assembly systems, RC inspires the development of walking worker assembly line (WWAL). On the other hand, U-type assembly lines (UALs) may provide higher worker utilization, lower space requirement and more convenient internal logistics when compared to straight assembly lines. In this context, this study aims to improve assembly line performance by generating RC cycles on WWAL with respect to task assignment characteristics of UAL within reasonable walking distance and space requirement. Therefore, a novel line configuration, namely, segmented rabbit chase-oriented U-type assembly line (SRCUAL), emerges.Design/methodology/approachThe mathematical programming approach treats SRCUAL balancing problem in a hierarchical manner to decrease computational burden. Firstly, segments are generated via the first linear programming model in the solution approach for balancing SRCUALs to minimize total number of workers. Then, stations are determined within each segment for forward and backward sections separately using two different pre-emptive goal programming models. Moreover, three heuristics are developed to provide solution quality with computational efficiency.FindingsThe proposed mathematical programming approach is applied to the light-emitting diode (LED) luminaire assembly section of a manufacturing company. The adaptation of SRCUAL decreased the number of workers by 15.4% and the space requirement by 17.7% for LED luminaire assembly system when compared to UAL. Moreover, satisfactory results for the proposed heuristics were obtained in terms of deviation from lower bound, especially for SRCUAL heuristics I and II. Moreover, the results indicate that the integration of RC not only decreased the number of workers in 40.28% (29 instances) of test problems in U-lines, but also yielded less number of buffer points (48.48%) with lower workload deviation (75%) among workers in terms of coefficient of variation.Practical implicationsThis study provides convenience for capacity management (assessing capacity and adjusting capacity by changing the number of workers) for industrial SRCUAL applications. Meanwhile, SRCUAL applications give the opportunity to increase the capacity for a product or transfer the saved capacity to the assembly of other products. As it is possible to provide one-piece flow with equal workloads via walking workers, SRCUAL has the potential for quick realization of defects and better lead time performance.Originality/valueTo the best of the authors’ knowledge, forward–backward task assignments in U-type lines have not been adapted to WWALs. Moreover, as workers travel overall the line in WWALs, walking time increases drastically. Addressing this research gap and limitation, the main innovative aspect of this study can be considered as the proposal of a new line design (i.e. SRCUAL) which is sourced from the hybridization of UALs and WWAL as well as the segmentation of the line with RC cycles. The superiority of SRCUAL over WWAL and UAL was also discussed. Moreover, operating systematic for SRCUAL was devised. As for methodical aspect, this study is the first attempt to solve the balancing problem for SRCUAL design.

Managing Multi-Discipline Extended Programmes

The Vaal University of Technology (VUT) has been offering a multidiscipline Extended Programme since 2009 and even though this Programme is made up from different faculties, the entire Extended Programme is overseen by one unit director.Due to the diversity of the unit and the variety of subject offerings, the unit simply cannot follow the same managerial approach that is applied when managing one specific discipline. That is why it requires a completely different and unique approach. The Extended Programme consists of students who are enrolled in different disciplines, i.e. Engineering, Human Sciences, etc., who all learn in different ways and have different needs, but are all managed in one specific unit. Therefore, to ensure that all needs of staff and students are catered for, it is crucial that an alternative managerial approach is applied.The success of a multidiscipline Extended Programme is dependent on the successes of the students, who in return are dependent on the dedication of both academic and administration staff. More so, the positive influence lecturers have on students and the invaluable role they play. It is undeniable that without the guidance and motivation of the lecturers it would be very difficult for the students to succeed. In order for the lecturers to be kept motivated and content, it is important to provide them with equal workloads and ensure transparency at all times. Staff, which is irrefutably guided and kept motivated by a suitable managerial approach. Applying this approach when managing a multidiscipline

Load-Balanced Parallel Streamline Generation on Large Scale Vector Fields

Because of the ever increasing size of output data from scientific simulations, supercomputers are increasingly relied upon to generate visualizations. One use of supercomputers is to generate field lines from large scale flow fields. When generating field lines in parallel, the vector field is generally decomposed into blocks, which are then assigned to processors. Since various regions of the vector field can have different flow complexity, processors will require varying amounts of computation time to trace their particles, causing load imbalance, and thus limiting the performance speedup. To achieve load-balanced streamline generation, we propose a workload-aware partitioning algorithm to decompose the vector field into partitions with near equal workloads. Since actual workloads are unknown beforehand, we propose a workload estimation algorithm to predict the workload in the local vector field. A graph-based representation of the vector field is employed to generate these estimates. Once the workloads have been estimated, our partitioning algorithm is hierarchically applied to distribute the workload to all partitions. We examine the performance of our workload estimation and workload-aware partitioning algorithm in several timings studies, which demonstrates that by employing these methods, better scalability can be achieved with little overhead.

Glucose Uptake Following Resistance Training Sessions of Different Intensities but of Equal Work Volume

Acute exercise and exercise training can have positive effects on insulin sensitivity and glucose uptake in healthy and glucose-intolerant subjects. An interest in resistance training and its effects on glucose uptake has increased in recent years. Past studies have indicated that high-intensity resistance exercise augments post-exercise glucose uptake to a greater degree than low-intensity resistance exercise. However, few studies have equated the work volumes among intensity levels, making it difficult to differentiate whether the resultant increased glucose uptake was due to the exercise intensity or the amount of work completed. To date, little is known about the effects that different exercise intensities, of equal workloads during a single session of resistance training, may have on glucose uptake. PURPOSE: To compare the effect of acute low- and high-intensity resistance exercise of equal work volume on glucose uptake in resistant-trained males. METHODS: Fifteen healthy male (22.9±3.8 y), resistance-trained (6.7 ±3.9 y) subjects completed three treatment sessions: CON (no-exercise control), HI (3 × 8, 85% 10-RM), and LO (3x15, 45% 10-RM). Exercise sessions consisted of eight resistance exercises. Glucose uptake was measured the following morning by hyperinsulinemic euglycemic clamp technique. Glucose disposal was measured by analyzing the glucose infusion rate during the final 30 minutes of steady-state blood glucose concentrations. Insulin sensitivity was calculated by dividing the glucose infusion rate by the average insulin infusion. RESULTS: Fasting blood glucose levels did not change among treatment sessions (CON=80.5± 5.3 vs. HI=77.0±4.9 vs. LO=77.1±6.0 mg/dl). Glucose uptake was not significantly different among treatment sessions (CON=11.3±3.0 vs. HI=11.7±2.7 vs. LO=11.4±2.8 mg/kgFFM/min). Insulin sensitivity did not change among treatment sessions [CON=0.26±0.09 vs. HI=0.28±0.07 vs. LO=0.27±0.06 (mg/kgFFM/min) / (uU/ml)]. CONCLUSIONS: These data indicate that for acute resistance exercise bouts with an equated work volume, low- and high-intensity sessions have similar effects on glucose uptake, but are no different than a no-exercise control session in resistance-trained men. The trained status of the subjects may have allowed for maximum training-induced cellular adaptations for enhanced insulin sensitivity and glucose uptake. Further investigations utilizing untrained males are warranted to further clarify the effects of intensity and workload on glucose uptake. Supported by the National Strength and Conditioning Association, the VCU-GCRC (M01 RR00065, NCRR, NIH), and the VCU School of Education

Effects of arterial oxygen content on peripheral locomotor muscle fatigue

The effect of arterial O2 content (Ca(O2)) on quadriceps fatigue was assessed in healthy, trained male athletes. On separate days, eight participants completed three constant-workload trials on a bicycle ergometer at fixed workloads (314 +/- 13 W). The first trial was performed while the subjects breathed a hypoxic gas mixture [inspired O2 fraction (Fi(O2)) = 0.15, Hb saturation = 81.6%, Ca(O2) = 18.2 ml O2/dl blood; Hypo] until exhaustion (4.5 +/- 0.4 min). The remaining two trials were randomized and time matched with Hypo. The second and third trials were performed while the subjects breathed a normoxic (Fi(O2) = 0.21, Hb saturation = 95.0%, Ca(O2) = 21.3 ml O2/dl blood; Norm) and a hyperoxic (Fi(O2) = 1.0, Hb saturation = 100%, Ca(O2) = 23.8 ml O2/dl blood; Hyper) gas mixture, respectively. Quadriceps muscle fatigue was assessed via magnetic femoral nerve stimulation (1-100 Hz) before and 2.5 min after exercise. Myoelectrical activity of the vastus lateralis was obtained from surface electrodes throughout exercise. Immediately after exercise, the mean force response across 1-100 Hz decreased from preexercise values (P < 0.01) by -26 +/- 2, -17 +/- 2, and -13 +/- 2% for Hypo, Norm, and Hyper, respectively; each of the decrements differed significantly (P < 0.05). Integrated electromyogram increased significantly throughout exercise (P < 0.01) by 23 +/- 3, 10 +/- 1, and 6 +/- 1% for Hypo, Norm, and Hyper, respectively; each of the increments differed significantly (P < 0.05). Mean power frequency fell more (P < 0.05) during Hypo (-15 +/- 2%); the difference between Norm (-7 +/- 1%) and Hyper (-6 +/- 1%) was not significant (P = 0.32). We conclude that deltaCa(O2) during strenuous systemic exercise at equal workloads and durations affects the rate of locomotor muscle fatigue development.

Reduction of queuing delays at waste management facilities

ile waiting to unload materials at waste management facilities such as landfill sites, transfer stations, and material recovery facilities. These delays can be costly since the program operator must pay for these trucks and their crews to sit idly. Previous studies of delays at unloading facilities have often focussed on reducing unloading times, primarily through capital improvements such as providing twin scale houses and additional unloading bays. Most of these studies assume that the "arrival pattern of the collection vehicles is beyond the control of the analyst. This work assumes that the physical layout of the unloading facility is fixed and examines the effect that changes in the arrival times of collection vehicles will have on queuing delays at the facility. Both deterministic and fluid flow approaches to the analysis of queuing delays at unloading facilities are presented. The results show that congestion at unloading facilities is often caused by the assignment of approximately equal workloads to each collection crew and that relatively minor differences in workload assignments can substantially reduce queuing delays. The results of the analysis are confirmed through Monte Carlo simulation modelling.

Effect of Cold Air on Exercise Capacity in COPD: Increase or Decrease?

Effect of Cold Air on Exercise Capacity in COPD: Increase or Decrease?

Differences in cardiorespiratory responses during and after arm crank and cycle exercise

The differences in cardiorespiratory responses were examined during and after intermittent progressive maximal arm-crank and cycle exercise. Arm-crank exercise was performed in a standing position using no torso restraints to maximize the amount of active skeletal muscle mass. Recovery was followed for 16 min. In the tests a variety of ventilatory gas exchange variables, heart rate, the blood pressure, and the arm venous blood lactate concentration were measured in 21 untrained healthy men aged 24-45 years. At equal submaximal external workloads for arm cranking and cycling (50 and 100 W) the respiratory frequency, tidal volume, pulmonary ventilation, oxygen uptake, carbon dioxide output, the respiratory exchange ratio, heart rate, the arm venous blood lactate concentration, and the ventilatory equivalent for oxygen were higher (P less than 0.001) during arm cranking than cycling. The maximal workload for arm cranking was 44% lower than that for cycling (155 +/- 37 vs 277 +/- 39 W, P less than 0.001) associated with significantly (P less than 0.001) lower maximal tidal volume (-20%), oxygen uptake (-22%), carbon dioxide output (-28%), systolic blood pressure (-17%) and oxygen pulse (-22%) but a higher ventilatory equivalent for carbon dioxide (+22%) and arm venous blood lactate concentration (+37%). However, these responses after arm-crank and cycle exercises behaved almost similarly during recovery. The high cardiorespiratory stress induced by arm work should be taken into account when the work stress and work-rest regimens in actual manual tasks are assessed, and when arm work is used for clinical testing, and in physiotherapy particularly for patients with heart or pulmonary diseases.

Circadian Variation of Cardiac Performance in Coronary Heart Disease

To study the circadian variation of cardiac performance in patients with coronary heart disease, three exercise tests on a bicycle crgometer were performed during the active part of the day (10 a.m., 2 p.m. and 6 p.m.), recording ST-segment depression and pulmonary capillary wedge pressure. Ten male patients with angiographically documented coronary heart disease underwent bicycle ergometry during placebo and during nitrate therapy (placebo controlled, double-blind crossover 2 × 20 mg IS-5-MN and 1 × 120 mg ISDN sustained release). During placebo as well as during nitrate therapy there was a gradual decrease of cardiac performance during the day, documented by the increase in ST-depression and pulmonary capillary wedge pressure at equal work loads. High nitrate concns led to a significant reduction of both ST-depression and preload with a marked circadian-phase dependency of cardiovascular effects.

Circadian Variation of Cardiac Performance in Coronary Heart Disease

To study the circadian variation of cardiac performance in patients with coronary heart disease, three exercise tests on a bicycle ergometer were performed during the active part of the day (10 a.m., 2 p.m. and 6 p.m.), recording ST-segment depression and pulmonary capillary wedge pressure. Ten male patients with angiographically documented coronary heart disease underwent bicycle ergometry during placebo and during nitrate therapy (placebo controlled, double-blind crossover 2 x 20 mg IS-5-MN and 1 x 120 mg ISDN sustained release). During placebo as well as during nitrate therapy there was a gradual decrease of cardiac performance during the day, documented by the increase in ST-depression and pulmonary capillary wedge pressure at equal work loads. High nitrate concns led to a significant reduction of both ST-depression and preload with a marked circadian-phase dependency of cardiovascular effects.

Optimal allocation of stratified samples with several variance constraints and equal workloads over time by geometric programming

We apply geometric programming, developed by Duffin, Peterson and Zener (1967), to the optimal allocation of stratified samples with several variance constraints arising from several estimates of deficiency rates in the quality control of administrative decisions. We develop also a method for imposing constraints on sample sizes to equalize workloads over time, as required by the practicalities of clerical work for quality control. We allocate samples by an extension of the work of Neyman (1934), following the exposition of Cochran (1977). Davis and Schwartz (1987) developed methods for multiconstraint Neyman allocation by geometric programming for integrated sampling. They also applied geometric programming to Neyman allocation of a sample for estimating college enrollments by Cornell (1947) and Cochran (1977). This paper continues the application of geometric programming to Neyman allocation with multiple constraints on variances and workloads and minimpal sampling costs.

The influence of the rotational energy of a flywheel on the load pulse sum during pedalling on a cycle ergometer

Employing seven male subjects, the influence of four different ergometer flywheels with the moments of inertia at the crankshaft (J') = 5.5, 10.5, 16.5, and 19.5 kg.m2 on 6-min load pulse sum (LPS), the heart rate integrated over 6-min was investigated. The J' was demonstrated to influence LPS at each of the corresponding rotational energies of the flywheels (75, 144, 226 and 276 J at 50 rev.min-1) in the four work-load steps (50, 100, 150 and 200 W). Between the values J' = 5.5 kg.m2 and 10.5 kg.m2 the LPS decreases, to rise again in the range J' = 10.5 kg.m2-19.5 kg.m2. For equal work-loads the minimum LPS was reached at a J' of 10.5 kg.m2. For the workloads of 100, 150 and 200 W it was possible to show statistically significant differences. The moment of inertia of ergometer flywheels J has a smoothing effect on the fluctuations of the rotational speed which are unavoidable during work on a cycle ergometer. The flywheel stores the leg forces acting on the pedals as rotational energy and opposes any rotational acceleration. If the J used is too small, equalization of the fluctuations of the rotational speed remains unsatisfactory. Flywheels with larger J require larger torques at the crankshaft for acceleration. For the most effective delivery of work to a cycle ergometer, an optimal rotational energy of the flywheel was found. For equal physical work, smaller or larger rotational energies require a larger expenditure of biological energy. A J' = 11 +/- 2 kg.m2 was incorporated into the draft for the German standard DIN 13,405 -- cycle-type ergometers.

Myocardial infarction size; effect on the training response

Myocardial infarction size; effect on the training response

Comparison of Cardiac Output during Work with Arms or Legs at Equal Work Loads

The effects of arm work and leg work on cardiac output (Q) and some other physiological parameters were studied in ten Japanese males. The subjects performed the work using arms or legs in a sitting position, with equal work loads of 150, 300, and 450kgm/min. Oxygen uptake (Vo2) and heart rate (HR) during arm work were significantly (P<0.01) higher than those during leg work at the loads of 300 and 450 kgm/min. With the increase of work loads, stroke volume (SV) during leg work was elevated, whereas no significant changes in SV occurred during arm work. At the heaviest load, SV during arm work was significantly (P<0.05) lower than that during leg work. There was no siginificant difference in Q between arm work and leg work at a given work load. The regression equation of Q(1/min ; Y) on Vo2 (ml/min ; X) was calculated for arm work and leg work, respectively, which was Y=2.37+0.00707X for arm work, and was Y=0.779+0.00968X for leg work. Analysis of covariance showed that the elevation of the regression equation calculated for arm work was significantly (P<0.05) lower than that for leg work. The regression equations of Q on Xo2 obtained during arm work and leg work in the present study were compared with those of some previous studies (BEVEGARD et al., 1966; STENBERG et al., 1967). Analysis of covariance indicated that those regression equations obtained during leg work were significantly different among each other. It should be noted that there were no significant differences in those regression equations obtained during arm work.

Training Response in Patients With Coronary Artery Disease Receiving β-Adrenergic Blocking Drugs With or Without Partial Agonist Activity

It has been suggested that beta-adrenoceptor blocking agents may impair the training response but that this may not occur if the agent possesses partial agonist activity (PAA). We tested these hypotheses in 39 male patients, following myocardial infarction or coronary artery bypass graft surgery, who underwent structured exercise training three times a week for 8 weeks. Exercise tolerance was assessed before training, within 5 days after training, and again 2 weeks after training in 14 patients receiving acebutolol (with PAA), 12 patients receiving sotalol (without PAA), and 13 patients receiving placebo. Blood levels of both agents confirmed that steady states sufficient to produce beta-blockade were achieved during training. All three groups of patients demonstrated statistically significant improvements in exercise duration, energy expenditure, heart rates attained performing equal work loads, and percentage functional aerobic impairment. No significant differences were found between the three groups before or after training. We conclude that beta-adrenoceptor blocking agents in standard therapeutic doses do not cause impairment of exercise training and that PAA affords no enhancement of the training response.

Dynamic and steady-state metabolic changes in running dogs

Dynamic and steady-state metabolic changes in running dogs

Transient O2 uptake response at the onset of exercise.

One purpose of this study was to determine whether the half time of the oxygen consumption (VO2) response at the onset of exercise varies with work intensity. Fifteen subjects performed 5 min of bicycle ergometer exercise across a range of relative work loads with VO2 determined continuously via computer analysis. The results revealed that the half time of the VO2 response increased as work intensity increased. Our second purpose was to determine whether VO2 response kinetics are dependent on the maximum oxygen uptake (VO2max) of the subject. When VO2 response kinetics were compared at equal absolute work loads for a highly trained (n = 8, mean VO2max = 70.2 ml/kg.min) and an untrained (n = 7, mean VO2max = 49.7 ml/kg.min) group, the highly trained group had a more rapid VO2 response (P less than 0.05). The same tendency was evident at equal relative work loads but the differences were not significant. The more rapid adaptation of the highly trained subjects at absolute work loads may be caused by the enzymatic and circulatory adaptations which result from endurance training. The more rapid adjustment of VO2 at the onset of exercise may explain the slower phosphagen and glycogen depletion found in highly trained subjects following short-term work at equal absolute loads.

Effect of body temperature on steady state ventilation and metabolism in exercise.

AbstractPetersen, E. S. and H. Vejby‐Christensen. Effect of body temperature on steady state ventilation and metabolism in exercise. Acta physiol. scand. 1073. 89. 342–351.Four healthy subjects were studied at rest and during steady slate of work at normal room and body temperature, and at elevated body temperature (38.5o C) in a climatic chamber. Ventilation, oxygen uptake, carbon dioxide elimination, heart rate, and blood lactate and pyruvate concentrations were measured. At equal work loads ventilation was not different, although respiratory rate was consistently higher and tidal volume lower at elevated temperature. Oxygen uptake was lower, and the ventilatory equivalent therefore higher in hyperthermia than in normothermia. Blood lactate concentration was higher both at rest and at all work loads indicating an increased anaerobic energy yield in hyperthermia. The study indicates the existence of a temperature threshold near 38o C, above which a relative hyperventilation is seen. The observed hyperventilation is hardly caused by changes in the [H+]‐stimulus, and it is suggested that hyperthermia per se or through interaction with other stimuli might constitute the additional ventilatory drive.