Effect of L-NAME on oxygen uptake kinetics during heavy-intensity exercise in the horse (original) (raw)
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Effect of L-NAME on oxygen uptake kinetics during heavy-intensity exercise in the horse (PDF
kinetics and the O 2 deficit in heavy exercise. J Appl Physiol 88: 1407-1412, 2000.-The purpose of this study was to examine a new method for calculating the O 2 deficit that considered the O 2 uptake (V O 2 ) kinetics during exercise as two separate phases in light of previous research in which it was shown that the traditional O 2 deficit calculation overestimated the recovery O 2 consumption (ROC). Eight subjects completed exercise transitions between unloaded cycling and 25% (heavy, H) or 50% (very heavy, VH) of the difference between the lactic acid threshold (LAT) and peak V O 2 for 8 min. The O 2 deficit, calculated in the traditional manner, was significantly greater than the measured ROC for both above-LAT exercises: 4.03 Ϯ 1.01 vs. 2.63 Ϯ 0.80 (SD) liters for VH and 2.36 Ϯ 0.91 vs. 1.74 Ϯ 0.63 liters for H for the O 2 deficit vs. ROC (P Ͻ 0.05). When the kinetics were viewed as two separate components with independent onsets, the calculated O 2 deficit (2.89 Ϯ 0.79 and 1.71 Ϯ 0.70 liters for VH and H, respectively) was not different from the measured ROC (P Ͻ 0.05). Subjects also performed the same work rate for only 3 min. These data, from bouts terminated before the slow component could contribute appreciably to the overall V O 2 response, show that the O 2 requirement during the transition is less than the final steady state for the work rate, as evidenced by symmetry between the O 2 deficit and ROC. This new method of calculating the O 2 deficit more closely reflects the expected O 2 deficit-ROC relationship (i.e., ROC Ն O 2 deficit). Therefore, estimation of the O 2 deficit during heavy exercise transitions should consider the slow component of V O 2 as an additional deficit component with delayed onset.
VO(2) kinetics and the O(2) deficit in heavy exercise
Journal of applied physiology (Bethesda, Md. : 1985), 2000
The purpose of this study was to examine a new method for calculating the O(2) deficit that considered the O(2) uptake (VO(2)) kinetics during exercise as two separate phases in light of previous research in which it was shown that the traditional O(2) deficit calculation overestimated the recovery O(2) consumption (ROC). Eight subjects completed exercise transitions between unloaded cycling and 25% (heavy, H) or 50% (very heavy, VH) of the difference between the lactic acid threshold (LAT) and peak VO(2) for 8 min. The O(2) deficit, calculated in the traditional manner, was significantly greater than the measured ROC for both above-LAT exercises: 4.03 +/- 1.01 vs. 2.63 +/- 0.80 (SD) liters for VH and 2.36 +/- 0.91 vs. 1.74 +/- 0.63 liters for H for the O(2) deficit vs. ROC (P < 0.05). When the kinetics were viewed as two separate components with independent onsets, the calculated O(2) deficit (2.89 +/- 0.79 and 1.71 +/- 0.70 liters for VH and H, respectively) was not different f...
A detailed comparison of oxygen uptake kinetics at a range of exercise intensities
Motriz: Revista de Educação Física, 2019
The aim of this study was to comprehensively examine oxygen uptake (V O 2) kinetics during cycling through mathematical modeling of the breath-by-breath gas exchange responses across eight conditions of unloaded cycling to moderate to high-intensity exercise. Methods: Following determination of GET and V O 2peak , eight participants (age: 24±8y; height: 1.78±0.09m; mass: 76.5±10.1kg; V O 2peak : 3.89±0.72 L. min-1) completed a series of square-wave rest-to-exercise transitions at;-20%∆ (GET minus 20% of the difference in V O 2 between that at GET and VO 2peak),-10%∆, GET, 10%∆, 20%∆, 30%∆, 40%∆, and 50%∆. The V O 2 kinetic response was modelled using mono-and bi-exponential non-linear regression techniques. The difference in the standard error of the estimates (SEE) for the mono-and bi-exponential models, and the slope of V O 2 vs time (for the final minute of exercise) were analysed using paired and one-sample t-tests, respectively. Results: The bi-exponential model SEE was lower than the monoexponential model across all exercise intensities (p<0.05), indicating a better model fit. Steady-state V O 2 was achieved across all exercise intensities (all V O 2 vs. time slopes; p>0.05). The modelled slow component time constants, typical of literature reported values, indicated that the V O 2 kinetic response would not be completed during the duration of the exercise. Conclusion: It was shown that the addition of the more complex bi-exponential model resulted in a better model fit across all intensities (notably including sub-GET intensities). The slow component phase was incomplete in all cases, even when the investigation of slopes indicated that a steady state had been achieved.
Slow component of O2 uptake during heavy exercise: adaptation to endurance training
Journal of applied physiology (Bethesda, Md. : 1985), 1995
Seven untrained male subjects [age 25.6 +/- 1.5 (SE) yr, peak O2 uptake (VO2) 3.20 +/- 0.19 l/min] trained on a cycle ergometer 4 days/wk for 6 wk, with the absolute training workload held constant for the duration of training. Before and at the end of each week of training, the subjects performed 20 min of constant-power exercise at a power designed to elicit a pronounced slow component of VO2 (end-exercise VO2-VO2 at minute 3 of exercise) in the pretraining session. An additional 20-min exercise bout was performed after training at this same absolute power output during which epinephrine (Epi) was infused at a rate of 100 ng.kg-1.min-1 between minutes 10 and 20. After 2 wk of training, significant decreases in VO2 slow component, end-exercise VO2, blood lactate ([La-] and glucose concentrations, plasma Epi ([Epi]) and norepinephrine concentrations, ventilation (VE), and heart rate (HR) were observed (P < 0.05). Although the rapid attenuation of the VO2 slow component coincided ...
Journal of Applied Physiology, 2005
The effect of prior heavy-intensity warm-up exercise on subsequent moderate-intensity phase 2 pulmonary O2 uptake kinetics (τV̇o2) was examined in young adults exhibiting relatively fast (FK; τV̇o2 < 30 s; n = 6) and slow (SK; τV̇o2 > 30 s; n = 6) V̇o2 kinetics in moderate-intensity exercise without prior warm up. Subjects performed four repetitions of a moderate (Mod1)-heavy-moderate (Mod2) protocol on a cycle ergometer with work rates corresponding to 80% estimated lactate threshold (moderate intensity) and 50% difference between lactate threshold and peak V̇o2 (heavy intensity); each transition lasted 6 min, and each was preceded by 6 min of cycling at 20 W. V̇o2 and heart rate (HR) were measured breath-by-breath and beat-by-beat, respectively; concentration changes of muscle deoxyhemoglobin (HHb), oxyhemoglobin, and total hemoglobin were measured by near-infrared spectroscopy (Hamamatsu NIRO 300). τV̇o2 was lower ( P < 0.05) in Mod2 than in Mod1 in both FK (20 ± 5 s vs....
Journal of applied physiology (Bethesda, Md. : 1985), 2002
We hypothesized that the elevated primary O(2) uptake (VO(2)) amplitude during the second of two bouts of heavy cycle exercise would be accompanied by an increase in the integrated electromyogram (iEMG) measured from three leg muscles (gluteus maximus, vastus lateralis, and vastus medialis). Eight healthy men performed two 6-min bouts of heavy leg cycling (at 70% of the difference between the lactate threshold and peak VO(2)) separated by 12 min of recovery. The iEMG was measured throughout each exercise bout. The amplitude of the primary VO(2) response was increased after prior heavy leg exercise (from mean +/- SE 2.11 +/- 0.12 to 2.44 +/- 0.10 l/min, P < 0.05) with no change in the time constant of the primary response (from 21.7 +/- 2.3 to 25.2 +/- 3.3 s), and the amplitude of the VO(2) slow component was reduced (from 0.79 +/- 0.08 to 0.40 +/- 0.08 l/min, P < 0.05). The elevated primary VO(2) amplitude after leg cycling was accompanied by a 19% increase in the averaged iEM...
Journal of applied physiology (Bethesda, Md. : 1985), 2001
The main purpose of this study was to investigate the effects of an 8-wk severe interval training program on the parameters of oxygen uptake kinetics, such as the oxygen deficit and the slow component, and their potential consequences on the time until exhaustion in a severe run performed at the same absolute velocity before and after training. Six endurance-trained runners performed, on a 400-m synthetic track, an incremental test and an all-out test, at 93% of the velocity at maximal oxygen consumption, to assess the time until exhaustion. These tests were carried out before and after 8 wk of a severe interval training program, which was composed of two sessions of interval training at 93% of the velocity at maximal oxygen consumption and three recovery sessions of continuous training at 60--70% of the velocity at maximal oxygen consumption per week. Neither the oxygen deficit nor the slow component were correlated with the time until exhaustion (r = -0.300, P = 0.24, n = 18 vs. r...
Journal of Applied Physiology, 2009
Jones, Andrew M., Helen Carter, Jamie S. M. Pringle, and Iain T. Campbell. Effect of creatine supplementation on oxygen uptake kinetics during submaximal cycle exercise. purpose of this study was to test the effect of oral creatine (Cr) supplementation on pulmonary oxygen uptake (V O2) kinetics during moderate [below ventilatory threshold (VT)] and heavy (above VT) submaximal cycle exercise. Nine subjects (7 men; means Ϯ SD: age 28 Ϯ 3 yr, body mass 73.2 Ϯ 5.6 kg, maximal V O2 46.4 Ϯ 8.0 ml ⅐ kg Ϫ1 ⅐ min Ϫ1 ) volunteered to participate in this study. Subjects performed transitions of 6-min duration from unloaded cycling to moderate (80% VT; 8-12 repeats) and heavy exercise (50% change; i.e., halfway between VT and maximal V O2; 4-6 repeats), both in the control condition and after Cr loading, in a crossover design. The Cr loading regimen involved oral consumption of 20 g/day of Cr monohydrate for 5 days, followed by a maintenance dose of 5 g/day thereafter. V O2 was measured breath by breath and modeled by using two (moderate) or three (heavy) exponential terms. For moderate exercise, there were no differences in the parameters of the V O2 kinetic response between control and Cr-loaded conditions. For heavy exercise, the time-based parameters of the V O2 response were unchanged, but the amplitude of the primary component was significantly reduced with Cr loading (means Ϯ SE: control 2.00 Ϯ 0.12 l/min; Cr loaded 1.92 Ϯ 0.10 l/min; P Ͻ 0.05) as was the end-exercise V O2 (control 2.19 Ϯ 0.13 l/min; Cr loaded 2.12 Ϯ 0.14 l/min; P Ͻ 0.05). The magnitude of the reduction in submaximal V O2 with Cr loading was significantly correlated with the percentage of type II fibers in the vastus lateralis (r ϭ 0.87; P Ͻ 0.01; n ϭ 7), indicating that the effect might be related to changes in motor unit recruitment patterns or the volume of muscle activated.
O2 uptake kinetics during exercise at peak O2 uptake
Journal of applied physiology (Bethesda, Md. : 1985), 2003
Compared with moderate- and heavy-intensity exercise, the adjustment of O2 uptake (VO2) to exercise intensities that elicit peak VO2 has received relatively little attention. This study examined the VO2 response of 21 young, healthy subjects (25 +/- 6 yr; mean +/- SD) during cycle ergometer exercise to step transitions in work rate (WR) corresponding to 90, 100, and 110% of the peak WR achieved during a preliminary ramp protocol (15-30 W/min). Gas exchange was measured breath by breath and interpolated to 1-s values. VO2 kinetics were determined by use of a two- or three-component exponential model to isolate the time constant (tau2) as representative of VO2 kinetics and the amplitude (Amp) of the primary fast component independent of the appearance of any VO2 slow component. No difference in VO2 kinetics was observed between WRs (tau90 = 24.7 +/- 9.0; tau100 = 22.8 +/- 6.7; tau110 = 21.5 +/- 9.2 s, where subscripts denote percent of peak WR; P > 0.05); nor in a subgroup of eight...