The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Maohui Luo - One of the best experts on this subject based on the ideXlab platform.
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human Metabolic Rate and thermal comfort in buildings the problem and challenge
Building and Environment, 2018Co-Authors: Maohui Luo, Zhe Wang, Bin Cao, Yongchao Zhai, Xiang ZhouAbstract:Abstract Of the six fundamental parameters in the classic heat balance model of human thermal comfort, Metabolic Rate is probably the most important and yet it is the most crudely assessed in both research and practice. Most studies in thermal comfort domain to date have relied on simple activity diaries to estimate Metabolic Rate. To better understand the pros and cons of this convenient approach, a literature review of cognate disciplines was conducted with the aim of transferring developments in human Metabolic science to the built environmental context. This review leads to the conclusion that the dairy methods prevalent in thermal comfort research and practice are probably not accuRate enough to sustain common thermal comfort modeling with any semblance of precision. Additional research effort is needed to develop better Metabolic Rate estimation methods for building occupants, especially accommodating individual differences in BMI, sex, age, pregnancy and menopause status, and non-steady state scenarios. In particular, three avenues of future research topics hold promise for improving practical Metabolic estimation and thermal comfort in buildings were discussed:1) development and validation of new Metabolic Rate instrumentation, 2) field measurement of human Metabolic Rate characteristics, 3) determine comfort zones for buildings with specific Metabolic Rate features.
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revisiting an overlooked parameter in thermal comfort studies the Metabolic Rate
Energy and Buildings, 2016Co-Authors: Maohui Luo, Xiang Zhou, Yingxin Zhu, Jan SundellAbstract:Abstract Human metabolism is a fundamental and important aspect of thermal comfort prediction. However, to date, most previous thermal comfort studies tended to treat Metabolic Rate as a constant value that only depends on activity level without consideration of ambient thermal conditions. In this paper, we explore the impacts of indoor thermal conditions on occupants’ Metabolic Rate and try to describe such impacts in a straightforward way. Climate chamber experiments, including both physiological measurements and subjective questionnaires, were conducted at temperatures ranging from cold to hot with two clothing insulation levels. The results indicate that human Metabolic Rate can be significantly affected by thermal conditions such as ambient temperature and clothing insulation. The changing trend of Metabolic Rate can be expressed as a second-order polynomial equation with actual thermal sensations or other predicted values. Generally, a neutral thermal sensation corresponds to the lowest Metabolic value, while the Metabolic Rate increases when thermal sensation departs from neutral to the cold or warm side. For instance, the Metabolic Rate at a sensation of ‘cold’ is 16.6% higher than it is in ‘neutral’ sensation. These findings, especially the modified equations describing Metabolic Rate changes, can serve as useful reference for future thermal comfort studies.
Craig R White - One of the best experts on this subject based on the ideXlab platform.
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short duration respirometry underestimates Metabolic Rate for discontinuous breathers
The Journal of Experimental Biology, 2018Co-Authors: Hugh S Winwoodsmith, Craig R WhiteAbstract:ABSTRACT Metabolic Rate is commonly estimated from Rates of gas exchange. An underappreciated factor that can influence estimates is patterns of pulmonary respiration. Amphibians display discontinuous respiratory patterns, often including long apnoeas, in addition to cutaneous gas exchange. The contribution of cutaneous exchange increases at low temperatures when Metabolic Rate is low. Because of the relatively low permeability of skin, measurements that disproportionately capture cutaneous exchange can produce underestimates of Metabolic Rate. The permeability of amphibian skin to CO2 is greater than that to O2; therefore, calculating the ratio of whole-animal CO2 emission to O2 uptake (the respiratory exchange ratio, RER) can be used to avoid underestimates of Metabolic Rate by ensuring that observed values of RER fall within the normal physiological range (∼0.7 to 1). Using data for cane toads, Rhinella marina, we show that short-duration measurements lead to underestimates of Metabolic Rate and overestimates of RER. At low temperatures, this problem is exacerbated, requiring over 12 h for RER to fall within the normal physiological range. Many published values of Metabolic Rate in animals that utilise cutaneous exchange may be underestimates.
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understanding variation in Metabolic Rate
The Journal of Experimental Biology, 2018Co-Authors: Amanda K Pettersen, Dustin J Marshall, Craig R WhiteAbstract:Metabolic Rate reflects an organism's capacity for growth, maintenance and reproduction, and is likely to be a target of selection. Physiologists have long sought to understand the causes and consequences of within-individual to among-species variation in Metabolic Rates - how Metabolic Rates relate to performance and how they should evolve. Traditionally, this has been viewed from a mechanistic perspective, relying primarily on hypothesis-driven approaches. A more agnostic, but ultimately more powerful tool for understanding the dynamics of phenotypic variation is through use of the breeder's equation, because variation in Metabolic Rate is likely to be a consequence of underlying microevolutionary processes. Here we show that Metabolic Rates are often significantly heritable, and are therefore free to evolve under selection. We note, however, that 'Metabolic Rate' is not a single trait: in addition to the obvious differences between Metabolic levels (e.g. basal, resting, free-living, maximal), Metabolic Rate changes through ontogeny and in response to a range of extrinsic factors, and is therefore subject to multivariate constraint and selection. We emphasize three key advantages of studying Metabolic Rate within a quantitative genetics framework: its formalism, and its predictive and comparative power. We make several recommendations when applying a quantitative genetics framework: (i) measuring selection based on actual fitness, rather than proxies for fitness; (ii) considering the genetic covariances between Metabolic Rates throughout ontogeny; and (iii) estimating genetic covariances between Metabolic Rates and other traits. A quantitative genetics framework provides the means for quantifying the evolutionary potential of Metabolic Rate and why variance in Metabolic Rates within populations might be maintained.
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The repeatability of Metabolic Rate declines with time
Journal of Experimental Biology, 2013Co-Authors: Craig R White, Natalie G. Schimpf, Phillip CasseyAbstract:The evolutionary causes of variation in Metabolic Rate within and among species are a topic of enduring interest. Variation between individuals is the raw material on which natural selection acts, and so recent years have seen an increase in the number of studies that examine the consequences of inter-individual differences in Metabolic Rate for organismal performance. A minimum requirement for a trait to evolve is that it must differ consistently between individuals, and these differences must be heritable. The time constancy of a trait is assessed by estimating its repeatability, which represents the ratio of the between-individual component of phenotypic variance to total phenotypic variance. A previous meta-analysis of repeatability concluded that Metabolic Rate is, on average, repeatable. Here, we expand on this earlier analysis by including extra data published in the intervening years and demonstRate that the repeatability of Metabolic Rate decreases as the interval between measurements increases.
Xiang Zhou - One of the best experts on this subject based on the ideXlab platform.
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human Metabolic Rate and thermal comfort in buildings the problem and challenge
Building and Environment, 2018Co-Authors: Maohui Luo, Zhe Wang, Bin Cao, Yongchao Zhai, Xiang ZhouAbstract:Abstract Of the six fundamental parameters in the classic heat balance model of human thermal comfort, Metabolic Rate is probably the most important and yet it is the most crudely assessed in both research and practice. Most studies in thermal comfort domain to date have relied on simple activity diaries to estimate Metabolic Rate. To better understand the pros and cons of this convenient approach, a literature review of cognate disciplines was conducted with the aim of transferring developments in human Metabolic science to the built environmental context. This review leads to the conclusion that the dairy methods prevalent in thermal comfort research and practice are probably not accuRate enough to sustain common thermal comfort modeling with any semblance of precision. Additional research effort is needed to develop better Metabolic Rate estimation methods for building occupants, especially accommodating individual differences in BMI, sex, age, pregnancy and menopause status, and non-steady state scenarios. In particular, three avenues of future research topics hold promise for improving practical Metabolic estimation and thermal comfort in buildings were discussed:1) development and validation of new Metabolic Rate instrumentation, 2) field measurement of human Metabolic Rate characteristics, 3) determine comfort zones for buildings with specific Metabolic Rate features.
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revisiting an overlooked parameter in thermal comfort studies the Metabolic Rate
Energy and Buildings, 2016Co-Authors: Maohui Luo, Xiang Zhou, Yingxin Zhu, Jan SundellAbstract:Abstract Human metabolism is a fundamental and important aspect of thermal comfort prediction. However, to date, most previous thermal comfort studies tended to treat Metabolic Rate as a constant value that only depends on activity level without consideration of ambient thermal conditions. In this paper, we explore the impacts of indoor thermal conditions on occupants’ Metabolic Rate and try to describe such impacts in a straightforward way. Climate chamber experiments, including both physiological measurements and subjective questionnaires, were conducted at temperatures ranging from cold to hot with two clothing insulation levels. The results indicate that human Metabolic Rate can be significantly affected by thermal conditions such as ambient temperature and clothing insulation. The changing trend of Metabolic Rate can be expressed as a second-order polynomial equation with actual thermal sensations or other predicted values. Generally, a neutral thermal sensation corresponds to the lowest Metabolic value, while the Metabolic Rate increases when thermal sensation departs from neutral to the cold or warm side. For instance, the Metabolic Rate at a sensation of ‘cold’ is 16.6% higher than it is in ‘neutral’ sensation. These findings, especially the modified equations describing Metabolic Rate changes, can serve as useful reference for future thermal comfort studies.
Klaas R. Westerterp - One of the best experts on this subject based on the ideXlab platform.
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Limits to sustainable human Metabolic Rate
Journal of Experimental Biology, 2001Co-Authors: Klaas R. WesterterpAbstract:SUMMARY There is a limit to the performance of an organism set by energy intake and energy mobilization. Here, the focus is on humans with unlimited access to food and for whom physical activity can be limited by energy mobilization. The physical activity level (PAL) in the general population, calculated as doubly-labelled-water-assessed average daily Metabolic Rate as a multiple of basal Metabolic Rate, has an upper limit of 2.2–2.5. The upper limit of sustainable Metabolic Rate is approximately twice as high in endurance athletes, mainly because of long-term exercise training with simultaneous consumption of carbohydRate-rich food during exercise. Endurance athletes have an increased fat-free mass and can maintain energy balance at a PAL value of 4.0–5.0. High altitude limits exercise performance as a result of combined effects on nutrient supply and the capacity to process nutrients. Thus, trained subjects climbing Mount Everest reached PAL values of 2.0–2.7, well below the observed upper limit at sea level.
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Physical activity and sleeping Metabolic Rate.
Medicine and science in sports and exercise, 1991Co-Authors: Klaas R. Westerterp, G. A. L. Meijer, Wim H. M. Saris, Peter B. Soeters, Yvonne Winants, Foppe Ten HoorAbstract:ABSTRACTWESTERTERP, K. R., G. A. L. MEIJER, W. H. M. SARIS, P. B. SOETERS, Y. WINANTS, and F. TEN HOOR. Physical activity and sleeping Metabolic Rate. Med. Sci. Sports Exerc., Vol. 23, No. 2, pp. 166–170, 1991. In the present investigation we determined Metabolic Rate during sleep (SMR) as a functio
Lindell Bromham - One of the best experts on this subject based on the ideXlab platform.
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Metabolic Rate does not calibRate the molecular clock
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Robert Lanfear, Jessica A Thomas, John J Welch, Thomas Brey, Lindell BromhamAbstract:Rates of molecular evolution vary widely among lineages, but the causes of this variation remain poorly understood. It has been suggested that mass-specific Metabolic Rate may be one of the key factors determining the Rate of molecular evolution, and that it can be used to derive “corrected” molecular clocks. However, previous studies have been hampered by a paucity of mass-specific Metabolic Rate data and have been largely limited to vertebRate taxa. Using mass-specific Metabolic Rate measurements and DNA sequence data for >300 metazoan species for 12 different genes, we find no evidence that mass-specific Metabolic Rate drives substitution Rates. The mechanistic basis of the Metabolic Rate hypothesis is discussed in light of these findings.