work rate
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Author(s):  
Uwe Hoffmann ◽  
Felix Faber ◽  
Uwe Drescher ◽  
Jessica Koschate

Abstract Purpose Kinetics of cardiorespiratory parameters (CRP) in response to work rate (WR) changes are evaluated by pseudo-random binary sequences (PRBS testing). In this study, two algorithms were applied to convert responses from PRBS testing into appropriate impulse responses to predict steady states values and responses to incremental increases in exercise intensity. Methods 13 individuals (age: 41 ± 9 years, BMI: 23.8 ± 3.7 kg m−2), completing an exercise test protocol, comprising a section of randomized changes of 30 W and 80 W (PRBS), two phases of constant WR at 30 W and 80 W and incremental WR until subjective fatigue, were included in the analysis. Ventilation ($$\dot{V}_{{\text{E}}}$$ V ˙ E ), O2 uptake ($$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 ), CO2 output ($$\dot{V}{\text{CO}}_{2}$$ V ˙ CO 2 ) and heart rate (HR) were monitored. Impulse responses were calculated in the time domain and in the frequency domain from the cross-correlations of WR and the respective CRP. Results The algorithm in the time domain allows better prediction for $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 and $$\dot{V}{\text{CO}}_{2}$$ V ˙ CO 2 , whereas for $$\dot{V}_{{\text{E}}}$$ V ˙ E and HR the results were similar for both algorithms. Best predictions were found for $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 and HR with higher (3–4%) 30 W steady states and lower (1–4%) values for 80 W. Tendencies were found in the residuals between predicted and measured data. Conclusion The CRP kinetics, resulting from PRBS testing, are qualified to assess steady states within the applied WR range. Below the ventilatory threshold, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 and HR responses to incrementally increasing exercise intensities can be sufficiently predicted.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Viorel Badescu

Abstract A general formalism is developed to evaluate the amount of work extractable from energy fluxes. It covers nonequilibrium cases when the concept of exergy is not relevant. The rate of work deficiency, which has been previously introduced as the total loss of exergy, is defined here as the total loss of work, which would have resulted if all the work were lost to the environment. New performance indicators are proposed. First, the work content factor gives the proportion of extractable work in a given amount of energy. Second, the work deficiency factor is a measure of the potential of improvement for the operation of energy conversion systems. Previous results reported in literature are particular cases of the general results obtained here. The formalism is used to evaluate the work rate extractable from the solar energy flux. Results are shown in cases where solar radiation interacts with materials without energy bandgap (metals) and with energy bandgaps (semiconductors), respectively.


2021 ◽  
Vol 8 ◽  
Author(s):  
Derek L. Tran ◽  
David S. Celermajer ◽  
Julian Ayer ◽  
Leeanne Grigg ◽  
Carley Clendenning ◽  
...  

Background: People with a Fontan circulation usually have moderately impaired exercise performance, although a subset have high physical performance (“Super-Fontan”), which may represent a low-risk phenotype.Methods: People with a “Super-Fontan” phenotype were defined as achieving normal exercise performance [≥80% predicted peak oxygen uptake (VO2) and work rate] during cardiopulmonary exercise testing (CPET) and were identified from the Australian and New Zealand Fontan Registry. A Fontan control group that included people with impaired exercise performance (<80% predicted VO2 or work rate) was also identified based on a 1:3 allocation ratio. A subset of participants were prospectively recruited and completed a series of physical activity, exercise self-efficacy, and health-related quality of life questionnaires.Results: Sixty CPETs (“Super-Fontan”, n = 15; control, n = 45) were included. A subset (“Super-Fontan”, n = 10; control, n = 13) completed a series of questionnaires. Average age was 29 ± 8 years; 48% were males. Exercise capacity reflected by percent predicted VO2 was 67 ± 17% in the entire cohort. Compared to the “Super-Fontan” phenotype, age at Fontan completion was higher in controls (4.0 ± 2.9 vs. 7.2 ± 5.3 years, p = 0.002). Only one (7%) person in the “Super-Fontan” group had a dominant right ventricle compared to 15 (33%) controls (p = 0.043). None of those in the “Super-Fontan” group were obese, while almost a quarter (22%) of controls were obese based on body mass index (p = 0.046). Lung function abnormalities were less prevalent in the “Super-Fontan” group (20 vs. 70%, p = 0.006). Exercise self-efficacy was greater in the “Super-Fontan” group (34.2 ± 3.6 vs. 27.9 ± 7.2, p = 0.02). Self-reported sports participation and physical activity levels during childhood and early adulthood were higher in the “Super-Fontan” group (p < 0.05). The total average time spent participating in structured sports and physical activity was 4.3 ± 2.6 h/wk in the “Super-Fontan” group compared to 2.0 ± 3.0 h/wk in controls, p = 0.003. There were no differences in self-reported current total physical activity score or health-related quality of life between groups (p ≥ 0.05).Conclusions: The “Super-Fontan” phenotype is associated with a healthy weight, lower age at Fontan completion, better exercise self-efficacy, and higher overall levels of sport and physical activity participation during physical development.


Author(s):  
João P. Jesus ◽  
Miguel Gomes ◽  
André D. Gonçalves ◽  
Joana M. Correia ◽  
Pedro Pezarat‐Correia ◽  
...  

Author(s):  
Reid A. Mitchell ◽  
Scott T. Apperely ◽  
Satvir S. Dhillon ◽  
Julia Zhang ◽  
Kyle G. Boyle ◽  
...  

This case report characterizes the physiological responses to incremental cycling and determines the effects of 12 weeks of inspiratory muscle training (IMT) on respiratory muscle strength, exercise capacity and dyspnea in a physically active 59-year-old female, four years after a left-sided extra-pleural pneumonectomy (EPP). On separate days, a symptom limited incremental exercise test and a constant work rate (CWR) test at 75% of peak work rate (WR) were completed, followed by 12 weeks of IMT and another CWR test. IMT consisted of two sessions of 30 repetitions twice daily for 5 days per week. Physiological and perceptual variables were measured throughout each exercise test. The participant had a total lung capacity that was 43% predicted post-EPP. A rapid and shallow breathing pattern was adopted throughout exercise, and the ratio of minute ventilation to carbon dioxide output was elevated for a given work rate. Oxygen uptake was 74%predicted and WR was 88%predicted. Following IMT, maximal inspiratory pressure improved by 36% (-27.1 cmH2O) and endurance time by 31s, with no observable changes in any submaximal or peak cardiorespiratory variables during exercise. The intensity and unpleasantness of dyspnea increased by 2 and 3 Borg 0-10 units, respectively, at the highest equivalent submaximal exercise time achieved on both tests. Despite having undergone a significant reduction in lung volume post-EPP, the participant achieved a relatively normal peak incremental WR, which may reflect a high level of physical conditioning. This case report also demonstrates that IMT can effectively increase respiratory muscle strength several years following EPP.


2021 ◽  
Author(s):  
Chantelle du Plessis ◽  
Mark Andrews ◽  
Lachlan Mitchell ◽  
Jodie Cochrane Wilkie ◽  
Trish King ◽  
...  

Severe-intensity constant work rate (CWR) cycling tests are useful for monitoring training progression and adaptation as they impose significant physiological and psychological strain and thus simulate the high-intensity competition environment. However, fatiguing tests require substantial recovery and may disrupt athlete training or competition preparation. Therefore, the development of a brief, minimally fatiguing test providing comparable information is desirable. Purpose : To determine whether physiological variables measured during, and functional decline in maximal power output immediately after, a 2-min CWR test can act as a proxy for 4-min test outcomes. Methods : Physiological stress was monitored and pre-to-post-CWR changes in 10-s sprint power computed (to estimate performance fatigability) during 2- and 4-min CWR tests in high-level cyclists. Results : The 2-min CWR test evoked a smaller decline in sprint mechanical power (32% vs. 47%, p <0.001), however both the physiological variables and sprint mechanical power were independently and strongly correlated between 2- and 4-min tests. Differences in V?O 2peak and blood lactate concentration in both CWR tests were strongly associated with the decline in sprint mechanical power. Conclusion : Physiological variables measured during, and the loss in sprint mechanical power measured after, a severe-intensity 2-min CWR test were less than in the 4-min test. Yet strong correlations between 2- and 4-min test outcomes indicated that the 2-min test can be used as a proxy for the longer test. Because shorter tests are less strenuous, they should have less impact on training and competition preparation and may therefore be more practically applicable within the elite performance environment.


Trials ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Harsh Parikh ◽  
Eric Lui ◽  
Marie E. Faughnan ◽  
Abdul Al-Hesayen ◽  
Stephanie Segovia ◽  
...  

Abstract Background The hepatopulmonary syndrome (HPS) is a pulmonary complication of liver disease found in 10 to 32% of patients with cirrhosis and is characterized by intrapulmonary vascular dilatations and abnormal oxygenation. Liver transplantation is the only effective therapy for this disease. Patients with HPS have significant exercise limitations, impacting their quality of life and associated with poor liver transplant outcomes. Many patients with HPS exhibit orthodeoxia—an improvement in oxygenation in the supine compared to the upright position. We hypothesize that exercise capacity will be superior in the supine compared to the upright position in such patients. Methods We propose a randomized controlled crossover trial in patients with moderate HPS (PaO2 < 80 mmHg) and orthodeoxia (supine to upright PaO2 decrease > 4 mmHg) comparing the effect of supine vs upright position on exercise. Patients with pulmonary hypertension, FEV1/FVC ratio < 0.65, significant coronary artery disease, disorders preventing or contraindicating use of a cycle ergometer, and/or moderate or severe ascites will be excluded. Participants will be randomized to cycle ergometry in either the supine or upright position. After a short washout period (a minimum of 1 day to a maximum of 4 weeks), participants will crossover and perform an exercise in the alternate position. Exercise will be performed at a constant work rate of 70–85% of the predicted peak work rate until the “stopping time” is reached, defined by exhaustion, profound desaturation, or safety concerns (drop in systolic blood pressure or life-threatening arrhythmia). The primary outcome will be the difference in the stopping time between exercise positions, compared with a repeated measures analysis of variance method with a mixed effects model approach. The model will be adjusted for period effects. P < 0.05 will be considered statistically significant. Discussion HPS patients have hypoxemia leading to significant exercise limitations. If our study is positive, a supine exercise regimen could become a routine prescription for patients with HPS and orthodeoxia, enabling them to exercise more effectively. Future studies could explore the corresponding effects of a supine exercise training regimen on physiologic variables such as long-term exercise capacity, quality of life, dyspnea, and liver transplantation outcomes. Trial registration ClinicalTrials.gov Protocol Registration and Results System (PRS) NCT04004104. Registered on 1 July 2019


2021 ◽  
pp. 12-18
Author(s):  
I. Yu. Anufrieva

The article is devoted to topical problems of labor rationing in organizations of the real sector of the economy. First, the author reveals the meaning and essence of labor rationing, gives a retrospective of approaches to labor rationing, clarifies the concept and content of intra-organizational labor rationing in modern conditions. Taking into account the possibilities of using modern information and communication technologies in the organization of labor rationing, due attention is not paid. In this regard, the leading organizations of various types of activities of the Altai Territory studied the features and modern problems of intra-organizational regulation of labor. The provision of the staff and the conditions for training specialists — work rate setters in organizations, the used normative reference books, the applied methods of work rate setting, assessed the quality level of the current labor standards. The author has systematized traditional and modern domestic and foreign methods of microelement rationing of labor. Based on the results of the study, the author presents specific recommendations for building a microelement regulatory framework for an organization in the context of digitalization. Among them deserve the greatest interest, according to the author, specific automated systems and programs for the rationing of labor, as well as the graphic-analytical method and the Gauss method.


Oecologia ◽  
2021 ◽  
Vol 197 (2) ◽  
pp. 365-371
Author(s):  
Jan-Åke Nilsson ◽  
Andreas Nord

AbstractMany birds and mammals show substantial circadian variation in body temperature, which has been attributed to fluctuations in ambient temperature and energy reserves. However, to fully understand the variation in body temperature over the course of the day, we also need to consider effects of variation in work rate. We made use of a dataset on body temperature during the resting and active periods in female marsh tits (Poecile palustris) that bred in a temperate area and were subjected to experimental changes in reproductive investment through brood size manipulations. Furthermore, the amplitude increased with daytime, but were unaffected by nighttime, ambient temperature. Amplitudes in females with manipulated broods were 44% above predictions based on inter-specific allometric relationships. In extreme cases, amplitudes were > 100% above predicted values. However, no individual female realised the maximum potential amplitude (8.5 °C, i.e. the difference between the highest and lowest body temperature within the population) but seemed to prioritise either a reduction in body temperature at night or an increase in body temperature in the day. This suggests that body temperature amplitude might be constrained by costs that preclude extensive use of both low nighttime and high daytime body temperatures within the same individual. Amplitudes in the range found here (0.5–6.7 °C) have previously mostly been reported from sub-tropical and/or arid habitats. We show that comparable values can also be found amongst birds in relatively cool, temperate regions, partly due to a pronounced increase in body temperature during periods with high work rate.


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