589 VENTILATORY AND CO2 OUTPUT KINETICS ARE SPEEDED DY PRIOR EXERCISE: AN EFFECT OF REDUCED MUSCLE CO, CAPACITANCE?

The effects of prior exercise on O2 uptake (VO2) kinetics during supra-lactate threshold (LT) cycling were assessed in 11 subjects. Protocols consisted of two consecutive 6-min work bouts separated by 0 W (6 min) with 1) both bouts sub-LT, 2) both bouts supra-LT, 3) bout 1 sub-LT and bout 2 supra-LT, and 4) bout 1 supra-LT and bout 2 sub-LT. Sub-LT VO2 kinetics were similar whether the prior bout was supra- or sub-LT. The VO2 kinetics for supra-LT work preceded by a sub-LT “warm-up” were similar to those for supra-LT work that was not preceded by exercise (O-W warm-up): the “partial”: O2 deficit averaged 2.64 vs. 2.57 liters, and the “effective” VO2 time constant averaged 56 vs. 65 s. Exercise responses (i.e., the change between O W and minute 6 of exercise) were unaffected for lactate concentration (4.58 vs. 4.50 meq/l), pH (-0.08 vs. -0.10), and CO2 output (VCO2; 2.65 vs. 2.49 l/min). However, when the supra-LT work was preceded by a supra-LT warm-up, VO2 kinetics were appreciably faster (O2 deficit = 1.82 liters, VO2 time constant = 37 s) relative to 0-W warm-up; the lactate (0.69 meq/l), pH (-0.01), and VCO2 (2.08 l/min) responses were smaller; and the effective VCO2 time constant was longer (58 vs. 43 s). The mechanism(s) that underlie this speeding of the VO2 kinetics cannot be firmly established, but we suggest that an improved muscle perfusion during the exercise may be involved consequent to the residual metabolic acidemia from the high-intensity warm-up.

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Effect of Prior Exercise Above and Below Critical Power on Exercise to Exhaustion

Yearbook of Sports Medicine ◽

10.1016/s0162-0908(08)70325-8 ◽

2006 ◽

Vol 2006 ◽

pp. 99-100

Author(s):

I. Shrier

Keyword(s):

Critical Power ◽

Prior Exercise

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Predicting Exercise-Related Changes in Glucose in People with Type 1 Diabetes Using Linear Models and Incorporating Knowledge of Prior Exercise

Diabetes ◽

10.2337/db18-751-p ◽

2018 ◽

Vol 67 (Supplement 1) ◽

pp. 751-P

Author(s):

NICHOLE S. TYLER ◽

RAVI REDDY ◽

JOSEPH EL YOUSSEF ◽

JESSICA R. CASTLE ◽

PETER G. JACOBS

Keyword(s):

Type 1 Diabetes ◽

Linear Models ◽

Prior Exercise

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Thermodynamic Study of Energy Consumption and Carbon Dioxide Emission in Ironmaking Process of the Reduction of Iron Oxides by Carbon

Energies ◽

10.3390/en14071999 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1999

Author(s):

Guanyong Sun ◽

Bin Li ◽

Hanjie Guo ◽

Wensheng Yang ◽

Shaoying Li ◽

...

Keyword(s):

Carbon Dioxide ◽

Energy Consumption ◽

Iron Oxides ◽

Volume Fraction ◽

Minimum Energy ◽

Carbon Dioxide Emission ◽

Reduction Reactions ◽

Co2 Output ◽

Coupling Parameters ◽

Ironmaking Process

Carbon included in coke and coal was used as a reduction agent and fuel in blast furnace (BF) ironmaking processes, which released large quantities of carbon dioxide (CO2). Minimizing the carbon consumption and CO2 output has always the goal of ironmaking research. In this paper, the reduction reactions of iron oxides by carbon, the gasification reaction of carbon by CO2, and the coupling reactions were studied by thermodynamic functions, which were derived from isobaric specific heat capacity. The reaction enthalpy at 298 K could not represent the heat value at the other reaction temperature, so the certain temperature should be confirmed by Gibbs frees energy and gas partial pressure. Based on Hess’ law, the energy consumption of the ironmaking process by carbon was calculated in detail. The decrease in the reduction temperature of solid metal iron has been beneficial in reducing the sensible heat required. When the volume ratio of CO to CO2 in the top gas of the furnace was given as 1.1–1.5, the coupling parameters of carbon gasification were 1.06–1.28 for Fe2O3, 0.71–0.85 for Fe3O4, 0.35–0.43 for FeO, respectively. With the increase in the coupling parameters, the volume fraction of CO2 decreased, and energy consumption and CO2 output increased. The minimum energy consumption and CO2 output of liquid iron production were in the reduction reactions with only CO2 generated, which were 9.952 GJ/t and 1265.854 kg/t from Fe2O3, 9.761 GJ/t and 1226.799 kg/t from Fe3O4, 9.007 GJ/t and 1107.368 kg/t from FeO, respectively. Compared with the current energy consumption of 11.65 GJ/t hot metal (HM) and CO2 output of 1650 kg/tHM of BF, the energy consumption and CO2 of ironmaking by carbon could reach lower levels by decreasing the coupled gasification reactions, lowering the temperature needed to generate solid Fe and adjusting the iron oxides to improve the iron content in the raw material. This article provides a simplified calculation method to understand the limit of energy consumption and CO2 output of ironmaking by carbon reduction iron oxides.

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Prior exercise does not alter the incretin response to a subsequent meal in obese women

Peptides ◽

10.1016/j.peptides.2015.07.004 ◽

2015 ◽

Vol 71 ◽

pp. 94-99 ◽

Cited By ~ 5

Author(s):

Lauryn M. Nyhoff ◽

Timothy D. Heden ◽

Heather J. Leidy ◽

Nathan C. Winn ◽

Young-Min Park ◽

...

Keyword(s):

Obese Women ◽

Prior Exercise

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Meal size and frequency: effect on potentiation of the thermal effect of food by prior exercise

European Journal of Applied Physiology and Occupational Physiology ◽

10.1007/bf00618495 ◽

1995 ◽

Vol 70 (5) ◽

pp. 437-441 ◽

Cited By ~ 5

Author(s):

John C. Young

Keyword(s):

Thermal Effect ◽

Meal Size ◽

Frequency Effect ◽

Prior Exercise ◽

Effect Of Food

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Responses of Lipolysis and Salivary Cortisol to Food Intake and Physical Activity in Lean and Obese Children

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2003-031144 ◽

2004 ◽

Vol 89 (9) ◽

pp. 4701-4707 ◽

Cited By ~ 21

Author(s):

A. M. Hershberger ◽

M. R. McCammon ◽

J. P. Garry ◽

M. T. Mahar ◽

R. C. Hickner

Keyword(s):

Physical Activity ◽

Adipose Tissue ◽

Salivary Cortisol ◽

Exercise Session ◽

Group Differences ◽

Cortisol Response ◽

Glycerol Concentration ◽

Glycerol Release ◽

Obese Children ◽

Prior Exercise

This investigation was conducted to determine whether there were differences in lipolytic responses to feeding and physical activity between lean (LN) and obese (OB) children, and if these responses were related to cortisol. Fourteen LN and 11 OB children participated in this study of abdominal lipolysis and salivary cortisol response to breakfast and lunch with an intervening exercise session. Calculated fasting glycerol release was lower in OB than LN (0.645 ± 0.06 vs. 0.942 ± 0.11 μmol/ml; P < 0.05). Fasting adipose tissue nutritive flow was lower in OB than in LN subjects, but responses to feeding and exercise were not different. Breakfast elicited a decrease in interstitial glycerol concentration in LN (−33%; P < 0.05), but not in OB (−5%), children, although decreases in glycerol concentration in response to lunch were similar (LN, −41%; OB, −36%). An interaction was evident in the salivary cortisol response to breakfast (LN, no change; OB, increase) and exercise (LN, no change; OB, decrease), but there were no group differences in response to lunch. Alterations in salivary cortisol and lipolysis were not related. These data suggest that salivary cortisol and lipolytic responses are not necessarily linked, but are altered in obesity. Furthermore, prior exercise may improve the antilipolytic response to a meal in OB children.

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Effect of interbreath fluctuations on characterizing exercise gas exchange kinetics

Journal of Applied Physiology ◽

10.1152/jappl.1987.62.5.2003 ◽

1987 ◽

Vol 62 (5) ◽

pp. 2003-2012 ◽

Cited By ~ 286

Author(s):

N. Lamarra ◽

B. J. Whipp ◽

S. A. Ward ◽

K. Wasserman

Keyword(s):

Gas Exchange ◽

Least Squares ◽

Kinetic Parameters ◽

Nonlinear Least Squares ◽

Cycle Ergometer ◽

Gaussian Stochastic Process ◽

Co2 Output ◽

Nonsteady State ◽

Exchange Kinetics ◽

Gas Exchange Kinetics

Breathing has inherent irregularities that produce breath-to-breath fluctuations (“noise”) in pulmonary gas exchange. These impair the precision of characterizing nonsteady-state gas exchange kinetics during exercise. We quantified the effects of this noise on the confidence of estimating kinetic parameters of the underlying physiological responses and hence of model discrimination. Five subjects each performed eight transitions from 0 to 100 W on a cycle ergometer. Ventilation, CO2 output, and O2 uptake were computed breath by breath. The eight responses were interpolated uniformly, time aligned, and averaged for each subject; and the kinetic parameters of a first-order model (i.e., the time constant and time delay) were then estimated using three methods: linear least squares, nonlinear least squares, and maximum likelihood. The breath-by-breath noise approximated an uncorrelated Gaussian stochastic process, with a standard deviation that was largely independent of metabolic rate. An expression has therefore been derived for the number of square-wave repetitions required for a specified parameter confidence using methods b and c; method a being less appropriate for parameter estimation of noisy gas exchange kinetics.

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Effect of peripheral chemoreceptor denervation on acclimatization of goats during hypoxia

Journal of Applied Physiology ◽

10.1152/jappl.1981.50.2.392 ◽

1981 ◽

Vol 50 (2) ◽

pp. 392-398 ◽

Cited By ~ 74

Author(s):

H. V. Forster ◽

G. E. Bisgard ◽

J. P. Klein

Keyword(s):

Sea Level ◽

Chronic Hypoxia ◽

Alveolar Ventilation ◽

Simulated Altitude ◽

Peripheral Chemoreceptor ◽

Peripheral Chemoreceptors ◽

Carotid Chemoreceptors ◽

Co2 Output

The purpose of this study was to determine the effect of peripheral chemoreceptor denervation on ventilatory acclimatization of goats during chronic hypoxia. After 1 h of stimulated altitude (PB 450 Torr), arterial O2 tension (PaO2) in seven normal goats averaged 42 Torr, and arterial CO2 tension (PaCO2) was 1.3 Torr below control (P less than 0.001). In these goats nearly 66% of the increase in alveolar ventilation (VA) associated with acclimatization occurred between 1.5 and 4 h of hypoxia. Acclimatization was complete by the 3rd day of hypoxia, and it caused 1) a 23% increase in VA/CO2 output (P less than 0.001); 2) a 5-Torr increase in PaO2 (P less than 0.001); and 3) a 6.5-Torr decrease in PaCO2 (P less than 0.001). Denervation of the carotid chemoreceptors in seven goats caused hypoventilation during eupnea at sea level (PaCO2 change from control +7 Torr, P less than 0.001). Denervation also attenuated but did not eliminate peripheral chemoreceptor responsiveness. No additional changes were observed following attempted denervation of the aortic chemoreceptors. After 1 h of simulated altitude (PB 530 Torr), PaO2 in the denervated goats averaged 46 Torr, and PaCO2 was increased 1.1 Torr above control (P less than 0.001). In these goats VA did not change significantly during the subsequent 3 days of hypoxia. Accordingly, we conclude that the peripheral chemoreceptors are essential for ventilatory acclimatization of goats during chronic hypoxia.

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