scholarly journals Repeat trial and breath averaging: Recommendations for research of VO2 kinetics of exercise transitions to steady-state

2019 ◽  
pp. 37-44 ◽  
Author(s):  
Craig Ryan McNulty ◽  
Robert Andrew Robergs
Keyword(s):  
Steady State ◽  
Total Error ◽  
Exponential Model ◽  
Oxygen Uptake Kinetics ◽  
Ventilation Threshold ◽  
Vo2 Kinetics ◽  
Exercise Transitions ◽  
Well Data ◽  
Kinetics Of ◽  
Male Subjects

Multiple-breath and multiple-trial averaging have been used extensively in research of oxygen uptake kinetics to steady-state. However, specific guidelines outlining correct levels of averaging have not been discussed. The aim of this study was to assess error differences using multiple-trial and multiple-breath averaging systems, and make recommendations for future VO2 kinetics research. Eight male subjects were recruited for this study. Following a maximal cycle test to ascertain each subject’s ventilation threshold, eight identical repetition cycling exercise bouts were administered. The bouts consisted of 6-minute at 85% of the subject’s ventilation threshold. Firstly, multiple-trial and multiple-breath data were processed using traditional methods. As well, data were fit using a mono-exponential model to derive tau. Data for all levels of multiple-trial and multiple-breath methods were compared to an 8-trial and 13-breath average, respectively. Reduction in error from the 3-trial average and a 3-breath average represented ∼68% and ∼70% of total error reduction, respectively. Tau tended to increase with increasing breath averaging and decrease with increasing trial averaging. There is negligible benefit to averaging more than 3 repeat trials in VO2 kinetics research. Breath averaging beyond 3-breaths artificially increases tau.

Oxygen uptake kinetics in treadmill running and cycle ergometry: a comparison

2000 ◽  
Vol 89 (3) ◽  
pp. 899-907 ◽  
Author(s):  
Helen Carter ◽  
Andrew M. Jones ◽  
Thomas J. Barstow ◽  
Mark Burnley ◽  
Craig A. Williams ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Slow Component ◽  
Maximal Oxygen Consumption ◽  
Exponential Model ◽  
Oxygen Uptake Kinetics ◽  
Treadmill Running ◽  
Tension Development ◽  
Exercise Transitions ◽  
The Difference ◽  
Power Outputs

The purpose of the present study was to comprehensively examine oxygen consumption (V˙o 2) kinetics during running and cycling through mathematical modeling of the breath-by-breath gas exchange responses to moderate and heavy exercise. After determination of the lactate threshold (LT) and maximal oxygen consumption (V˙o 2 max) in both cycling and running exercise, seven subjects (age 26.6 ± 5.1 yr) completed a series of “square-wave” rest-to-exercise transitions at running speeds and cycling power outputs that corresponded to 80% LT and 25, 50, and 75%Δ (Δ being the difference between LT andV˙o 2 max).V˙o 2 responses were fit with either a two- (<LT) or three-phase ( >LT) exponential model. The parameters of theV˙o 2 kinetic response were similar between exercise modes, except for the V˙o 2 slow component, which was significantly ( P < 0.05) greater for cycling than for running at 50 and 75%Δ (334 ± 183 and 430 ± 159 ml/min vs. 205 ± 84 and 302 ± 154 ml/min, respectively). We speculate that the differences between the modes are related to the higher intramuscular tension development in heavy cycle exercise and the higher eccentric exercise component in running. This may cause a relatively greater recruitment of the less efficient type II muscle fibers in cycling.

Simulation of pulmonary O2 uptake during exercise transients in humans

1987 ◽  
Vol 63 (6) ◽  
pp. 2253-2261 ◽  
Author(s):  
T. J. Barstow ◽  
P. A. Mole
Keyword(s):  
Blood Flow ◽  
Phase 1 ◽  
Muscle Metabolism ◽  
Exponential Model ◽  
Model Parameters ◽  
Second Phase ◽  
Phase 2 ◽  
O2 Uptake ◽  
Vo2 Kinetics ◽  
Kinetics Of

Computer simulation of blood flow and O2 consumption (QO2) of leg muscles and of blood flow through other vascular compartments was made to estimate the potential effects of circulatory adjustments to moderate leg exercise on pulmonary O2 uptake (VO2) kinetics in humans. The model revealed a biphasic rise in pulmonary VO2 after the onset of constant-load exercise. The length of the first phase represented a circulatory transit time from the contracting muscles to the lung. The duration and magnitude of rise in VO2 during phase 1 were determined solely by the rate of rise in venous return and by the venous volume separating the muscle from the lung gas exchange sites. The second phase of VO2 represented increased muscle metabolism (QO2) of exercise. With the use of a single-exponential model for muscle QO2 and physiological estimates of other model parameters, phase 2 VO2 could be well described as a first-order exponential whose time constant was within 2 s of that for muscle QO2. The use of unphysiological estimates for certain parameters led to responses for VO2 during phase 2 that were qualitatively different from QO2. It is concluded that 1) the normal response of VO2 in humans to step increases in muscle work contains two components or phases, the first determined by cardiovascular phenomena and the second primarily reflecting muscle metabolism and 2) the kinetics of VO2 during phase 2 can be used to estimate the kinetics of muscle QO2. The simulation results are consistent with previously published profiles of VO2 kinetics for square-wave transients.

Kinetic analysis of mechanism of intestinal Na+-dependent sugar transport

1985 ◽  
Vol 248 (5) ◽  
pp. C498-C509 ◽  
Author(s):  
D. Restrepo ◽  
G. A. Kimmich
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Sugar Transport ◽  
Enzyme Kinetic ◽  
Steady State Distribution ◽  
State Distribution ◽  
Least Squares Fit ◽  
Coupling Stoichiometry ◽  
Rate Limiting ◽  
Kinetics Of

Zero-trans kinetics of Na+-sugar cotransport were investigated. Sugar influx was measured at various sodium and sugar concentrations in K+-loaded cells treated with rotenone and valinomycin. Sugar influx follows Michaelis-Menten kinetics as a function of sugar concentration but not as a function of Na+ concentration. Nine models with 1:1 or 2:1 sodium:sugar stoichiometry were considered. The flux equations for these models were solved assuming steady-state distribution of carrier forms and that translocation across the membrane is rate limiting. Classical enzyme kinetic methods and a least-squares fit of flux equations to the experimental data were used to assess the fit of the different models. Four models can be discarded on this basis. Of the remaining models, we discard two on the basis of the trans sodium dependence and the coupling stoichiometry [G. A. Kimmich and J. Randles, Am. J. Physiol. 247 (Cell Physiol. 16): C74-C82, 1984]. The remaining models are terter ordered mechanisms with sodium debinding first at the trans side. If transfer across the membrane is rate limiting, the binding order can be determined to be sodium:sugar:sodium.

scholarly journals Kinetics of Biofilm Detachment

1992 ◽  
Vol 26 (9-11) ◽  
pp. 1995-1998 ◽  
Author(s):  
B. M. Peyton ◽  
W. G. Characklis
Keyword(s):  
Steady State ◽  
Utilization Rate ◽  
Carbon Utilization ◽  
Biofilm Thickness ◽  
First Order ◽  
Detachment Rate ◽  
Biofilm Detachment ◽  
Biofilm Modeling ◽  
Kinetics Of ◽  
Sensitive Variable

In predictive biofilm modeling, the detachment rate coefficient may be the most sensitive variable affecting both the predicted rate and the extent of biofilm accumulation. At steady state the detachment rate must be equal to the net growth rate in the biofilm. In systems where organic carbon is growth-limiting, the substrate carbon utilization rate determines the net biomass production rate and, therefore, the steady state biomass detachment rate. Detachment rates, first order with biofilm thickness, fit the experimental data well, but are not predictive since the coefficients must be determined experimentally.

Sign in / Sign up

Export Citation Format

Share Document