Kinetics of oxygen uptake during supine and upright heavy exercise

1999 ◽  
Vol 87 (1) ◽  
pp. 253-260 ◽  
Author(s):  
Shunsaku Koga ◽  
Tomoyuki Shiojiri ◽  
Manabu Shibasaki ◽  
Narihiko Kondo ◽  
Yoshiyuki Fukuba ◽  
...  
Keyword(s):  
Heart Rate ◽  
Oxygen Uptake ◽  
Supine Position ◽  
Slow Component ◽  
Fast Component ◽  
Heavy Exercise ◽  
The Difference ◽  
Early Rise ◽  
Kinetics Of ◽  
State Increase

It is presently unclear how the fast and slow components of pulmonary oxygen uptake (V˙o 2) kinetics would be altered by body posture during heavy exercise [i.e., above the lactate threshold (LT)]. Nine subjects performed transitions from unloaded cycling to work rates representing moderate (below the estimated LT) and heavy exercise (V˙o 2 equal to 50% of the difference between LT and peakV˙o 2) under conditions of upright and supine positions. During moderate exercise, the steady-state increase in V˙o 2was similar in the two positions, butV˙o 2 kinetics were slower in the supine position. During heavy exercise, the rate of adjustment ofV˙o 2 to the 6-min value was also slower in the supine position but was characterized by a significant reduction in the amplitude of the fast component ofV˙o 2, without a significant slowing of the phase 2 time constant. However, the amplitude of the slow component was significantly increased, such that the end-exerciseV˙o 2 was the same in the two positions. The changes inV˙o 2 kinetics for the supine vs. upright position were paralleled by a blunted response of heart rate at 2 min into exercise during supine compared with upright heavy exercise. Thus the supine position was associated with not only a greater amplitude of the slow component forV˙o 2 but also, concomitantly, with a reduced amplitude of the fast component; this latter effect may be due, at least in part, to an attenuated early rise in heart rate in the supine position.

Kinetics of oxygen uptake at the onset of exercise near or above peak oxygen uptake

2000 ◽  
Vol 88 (5) ◽  
pp. 1812-1819 ◽  
Author(s):  
R. L. Hughson ◽  
D. D. O'Leary ◽  
A. C. Betik ◽  
H. Hebestreit
Keyword(s):  
Oxygen Uptake ◽  
Cardiovascular System ◽  
Time Constant ◽  
Exponential Model ◽  
Peak Oxygen Uptake ◽  
Phase 2 ◽  
Heavy Exercise ◽  
The Difference ◽  
Kinetics Of ◽  
Model Phase

We tested the hypothesis that kinetics of O2 uptake (V˙o 2) measured in the transition to exercise near or above peakV˙o 2(V˙o 2 peak) would be slower than those for subventilatory threshold exercise. Eight healthy young men exercised at ∼57, ∼96, and ∼125%V˙o 2 peak. Data were fit by a two- or three-component exponential model and with a semilogarithmic transformation that tested the difference between required V˙o 2 and measuredV˙o 2. With the exponential model, phase 2 kinetics appeared to be faster at 125% V˙o 2 peak[time constant (τ2) = 16.3 ± 8.8 (SE) s] than at 57%V˙o 2 peak(τ2 = 29.4 ± 4.0 s) but were not different from that at 96%V˙o 2 peakexercise (τ2 = 22.1 ± 2.1 s).V˙o 2 at the completion of phase 2 was 77 and 80%V˙o 2 peak in tests predicted to require 96 and 125%V˙o 2 peak. WhenV˙o 2 kinetics were calculated with the semilogarithmic model, the estimated τ2 at 96%V˙o 2 peak (49.7 ± 5.1 s) and 125%V˙o 2 peak (40.2 ± 5.1 s) were slower than with the exponential model. These results are consistent with our hypothesis and with a model in which the cardiovascular system is compromised during very heavy exercise.

The Effect of Prior Moderate- and Heavy-Intensity Running on the VO2 Response to Exhaustive Severe-Intensity Running

2006 ◽  
Vol 1 (4) ◽  
pp. 361-374 ◽  
Author(s):  
Stephen B. Draper ◽  
Dan M. Wood ◽  
Jo Corbett ◽  
David V.B. James ◽  
Christopher R. Potter
Keyword(s):  
Oxygen Uptake ◽  
Slow Component ◽  
Maximum Oxygen Uptake ◽  
Moderate Intensity ◽  
Time To Exhaustion ◽  
Heavy Exercise ◽  
Square Wave ◽  
Severe Intensity ◽  
The Difference ◽  
Trained Runners

We tested the hypothesis that prior heavy-intensity exercise reduces the difference between asymptotic oxygen uptake (VO2) and maximum oxygen uptake (VO2max) during exhaustive severe-intensity running lasting ≍2 minutes. Ten trained runners each performed 2 ramp tests to determine peak VO2 (VO2peak) and speed at venti-latory threshold. They performed exhaustive square-wave runs lasting ≍2 minutes, preceded by either 6 minutes of moderate-intensity running and 6 minutes rest (SEVMOD) or 6 minutes of heavy-intensity running and 6 minutes rest (SEVHEAVY). Two transitions were completed in each condition. VO2 was determined breath by breath and averaged across the 2 repeats of each test; for the square-wave test, the averaged VO2 response was then modeled using a monoexponential function. The amplitude of the VO2 response to severe-intensity running was not different in the 2 conditions (SEVMOD vs SEVHEAVY; 3925 ± 442 vs 3997 ± 430 mL/min, P = .237), nor was the speed of the response (τ; 9.2 ± 2.1 vs 10.0 ± 2.1 seconds, P = .177). VO2peak from the square-wave tests was below that achieved in the ramp tests (91.0% ± 3.2% and 92.0% ± 3.9% VO2peak, P < .001). There was no difference in time to exhaustion between conditions (110.2 ± 9.7 vs 111.0 ± 15.2 seconds, P = .813). The results show that the primary VO2 response is unaffected by prior heavy exercise in running performed at intensities at which exhaustion will occur before a slow component emerges.

Cardiovascular and Oxygen Uptake Kinetics During Sequential Heavy Cycling Exercises

2003 ◽  
Vol 28 (2) ◽  
pp. 283-298 ◽  
Author(s):  
Stéphane Perrey ◽  
Jodie Scott ◽  
Laurent Mourot ◽  
Jean-Denis Rouillon
Keyword(s):  
Cardiac Output ◽  
Oxygen Uptake ◽  
Time Constant ◽  
Impedance Cardiography ◽  
Ventilatory Threshold ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Cycle Ergometer ◽  
Fast Component ◽  
Heavy Exercise

The purpose of the present study was to assess the relationship between the rapidity of increased oxygen uptake [Formula: see text] and increased cardiac output (CO) during heavy exercise. Six subjects performed repeated bouts on a cycle ergometer above the ventilatory threshold (∼80% of peak [Formula: see text]) separated by 10-min recovery cycling at 35% peak [Formula: see text]. [Formula: see text] was determined breath-by-breath and CO was determined continuously by impedance cardiography. CO and [Formula: see text] values were significantly higher during the 2-min period preceding the second bout. The overall responses for [Formula: see text] and CO were significantly related and were faster during the second bout. Prior heavy exercise resulted in a significant increase in the amplitude of the fast component of [Formula: see text] with no change in the time constant and a decrease in the slow component. Under these circumstances, the amplitude of the fast component was more sensitive to prior heavy exercise than was the associated time constant. Key words: impedance cardiography, exercise transitions, cardiac output, prior exercise

scholarly journals Oxygen uptake kinetics during treadmill running in boys and men

2001 ◽  
Vol 90 (5) ◽  
pp. 1700-1706 ◽  
Author(s):  
Craig A. Williams ◽  
Helen Carter ◽  
Andrew M. Jones ◽  
Jonathan H. Doust
Keyword(s):  
Oxygen Uptake ◽  
Time Constant ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Primary Response ◽  
Treadmill Running ◽  
Initial Increase ◽  
Moderate Exercise ◽  
Heavy Exercise ◽  
The Difference

The purpose of this study was to compare the kinetics of the oxygen uptake (V˙o 2) response of boys to men during treadmill running using a three-phase exponential modeling procedure. Eight boys (11–12 yr) and eight men (21–36 yr) completed an incremental treadmill test to determine lactate threshold (LT) and maximum V˙o 2. Subsequently, the subjects exercised for 6 min at two different running speeds corresponding to 80% of V˙o 2 at LT (moderate exercise) and 50% of the difference betweenV˙o 2 at LT and maximumV˙o 2 (heavy exercise). For moderate exercise, the time constant for the primary response was not significantly different between boys [10.2 ± 1.0 (SE) s] and men (14.7 ± 2.8 s). The gain of the primary response was significantly greater in boys than men (239.1 ± 7.5 vs. 167.7 ± 5.4 ml · kg−1 · km−1; P < 0.05). For heavy exercise, theV˙o 2 on-kinetics were significantly faster in boys than men (primary response time constant = 14.9 ± 1.1 vs. 19.0 ± 1.6 s; P < 0.05), and the primary gain was significantly greater in boys than men (209.8 ± 4.3 vs. 167.2 ± 4.6 ml · kg−1 · km−1; P < 0.05). The amplitude of theV˙o 2 slow component was significantly smaller in boys than men (19 ± 19 vs. 289 ± 40 ml/min; P < 0.05). The V˙o 2responses at the onset of moderate and heavy treadmill exercise are different between boys and men, with a tendency for boys to have faster on-kinetics and a greater initial increase inV˙o 2 for a given increase in running speed.

Effect of increased muscle temperature on oxygen uptake kinetics during exercise

1997 ◽  
Vol 83 (4) ◽  
pp. 1333-1338 ◽  
Author(s):  
Shunsaku Koga ◽  
Tomoyuki Shiojiri ◽  
Narihiko Kondo ◽  
Thomas J. Barstow
Keyword(s):  
Oxygen Uptake ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Work Rate ◽  
Uptake Kinetics ◽  
Hot Water ◽  
Muscle Temperature ◽  
Appreciable Effect ◽  
Heavy Exercise ◽  
The Difference

Koga, Shunsaku, Tomoyuki Shiojiri, Narihiko Kondo, and Thomas J. Barstow. Effect of increased muscle temperature on oxygen uptake kinetics during exercise. J. Appl. Physiol. 83(4): 1333–1338, 1997.—To test whether increased muscle temperature (Tm) would improve O2 uptake (V˙o 2) kinetics, seven men performed transitions from rest to a moderate work rate [below the estimated lactate threshold (LTest)] and a heavy work rate (V˙o 2 = 50% of the difference between LTest and peakV˙o 2) under conditions of normal Tm (N) and increased Tm (H), produced by wearing hot water-perfused pants before exercise. Quadriceps Tm was significantly higher in H, but rectal temperature was similar for the two conditions. There were no significant differences in the amplitudes of the fast component ofV˙o 2 or in the time constants of the on and off transients for moderate and heavy exercise between the two conditions. The increment inV˙o 2 between the 3rd and 6th min of heavy exercise was slightly but significantly smaller for H than for N. These data suggest that elevated Tm before exercise onset, which would have been expected to increase O2 delivery and off-loading to the muscle, had no appreciable effect on the fast exponential component ofV˙o 2 kinetics (invariant time constant). These data further suggest that elevated Tm does not contribute to the slow component of V˙o 2 during heavy exercise.

scholarly journals Effects of hypoxic hypoxia on O2 uptake and heart rate kinetics during heavy exercise

1996 ◽  
Vol 81 (6) ◽  
pp. 2500-2508 ◽  
Author(s):  
Marielle Engelen ◽  
Janos Porszasz ◽  
Marshall Riley ◽  
Karlman Wasserman ◽  
Kazuhira Maehara ◽  
...  
Keyword(s):  
Heart Rate ◽  
Time Constant ◽  
Slow Component ◽  
Hypoxic Hypoxia ◽  
Baseline Heart Rate ◽  
Heavy Exercise ◽  
Rate Kinetics ◽  
Lactic Acidosis Threshold ◽  
Kinetics Of ◽  
Heart Rate Kinetics

Engelen, Marielle, Janos Porszasz, Marshall Riley, Karlman Wasserman, Kazuhira Maehara, and Thomas J. Barstow. Effects of hypoxic hypoxia on O2 uptake and heart rate kinetics during heavy exercise. J. Appl. Physiol. 81(6): 2500–2508, 1996.—It is unclear whether hypoxia alters the kinetics of O2 uptake (V˙o 2) during heavy exercise [above the lactic acidosis threshold (LAT)] and how these alterations might be linked to the rise in blood lactate. Eight healthy volunteers performed transitions from unloaded cycling to the same absolute heavy work rate for 8 min while breathing one of three inspired O2 concentrations: 21% (room air), 15% (mild hypoxia), and 12% (moderate hypoxia). Breathing 12% O2 slowed the time constant but did not affect the amplitude of the primary rise inV˙o 2 (period of first 2–3 min of exercise) and had no significant effect on either the time constant or the amplitude of the slowV˙o 2 component (beginning 2–3 min into exercise). Baseline heart rate was elevated in proportion to the severity of the hypoxia, but the amplitude and kinetics of increase during exercise and in recovery were unaffected by level of inspired O2. We conclude that the predominant effect of hypoxia during heavy exercise is on the early energetics as a slowed time constant forV˙o 2 and an additional anaerobic contribution. However, the sum total of the processes representing the slow component ofV˙o 2 is unaffected.

Adjustment for gas exchange threshold enhances precision of heart rate-derived VO2 estimates during heavy exercise

2008 ◽  
Vol 33 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Robert W. Pettitt ◽  
J. David Symons ◽  
Julie E. Taylor ◽  
Patricia A. Eisenman ◽  
Andrea T. White
Keyword(s):  
Heart Rate ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Interval Training ◽  
Heart Rate Reserve ◽  
Heavy Exercise ◽  
Model Interaction ◽  
Fitness Level ◽  
The Difference ◽  
Gas Exchange Threshold

Overestimates of oxygen uptake (VO2) are derived from the heart rate reserve – VO2 reserve (HRR–VO2R) model. We tested the hypothesis that adjusting for differences above and below gas exchange threshold (HRR–GET model) would tighten the precision of HR-derived VO2 estimates during heavy exercise. Seven men and 7 women of various VO2 max levels, on 2 separate days, cycled for 6 min at intensities equal to power at GET, 15% the difference between GET and VO2 max (15% above), and at 30% above GET. A second bout at 15% above GET (15% above (bout 2)) after 3 min of recovery was performed to assess estimates during interval training. Actual VO2 was compared with estimates derived from the HRR–VO2R and the HRR–GET. VO2 values were summed over the 6 min duration of data collection (6 min LO2) and compared with Bland–Altman plots. HRR–VO2R yielded 6 min LO2 (±2 SD) overestimates of 2.0 (±2.5), 1.9 (±2.7), and 1.3 (±3.3) for GET, 15% over, and 30% over, respectively, whereas corresponding 6 min LO2 difference values for the HRR–GET model were –0.42 (±1.6), –0.23 (±1.1), and –0.55 (±1.8), respectively. For 15% above (bout 2), the 6 min LO2 difference for HRR–VO2R was 1.8 (±2.9), whereas the difference for HRR–GET was 0.17 (±1.4). The 6 min LO2 values relative to the subjects’ VO2 max did not vary (r = 0.05 to 0.36); therefore, fitness level did not affect estimates. Sex did not affect accuracy of either estimate model (sex X estimate model interaction, p > 0.95). We observed accurate estimates from the HRR–GET model during heavy exercise.

scholarly journals Longitudinal Changes in the Oxygen Uptake Kinetic Response to Heavy-Intensity Exercise in 14- to 16-Year-Old Boys

2010 ◽  
Vol 22 (2) ◽  
pp. 314-325 ◽  
Author(s):  
Brynmor C. Breese ◽  
Craig A. Williams ◽  
Alan R. Barker ◽  
Joanne R. Welsman ◽  
Samantha G. Fawkner ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Slow Component ◽  
Uptake Kinetic ◽  
Pulmonary Oxygen Uptake ◽  
Longitudinal Changes ◽  
Age Dependent ◽  
Constant Work Rate ◽  
Exercise Transitions ◽  
The Difference ◽  
Gas Exchange Threshold

This study examined longitudinal changes in the pulmonary oxygen uptake (pV̇O2) kinetic response to heavy-intensity exercise in 14–16 yr old boys. Fourteen healthy boys (age 14.1 ± 0.2 yr) completed exercise testing on two occasions with a 2-yr interval. Each participant completed a minimum of three ‘step’ exercise transitions, from unloaded pedalling to a constant work rate corresponding to 40% of the difference between the pV̇O2 at the gas exchange threshold and peak pV̇O2 (40% Δ). Over the 2-yr period a significant increase in the phase II time constant (25 ± 5 vs. 30 ± 5 s; p = .002, ω2 = 0.34), the relative amplitude of the pV̇O2 slow component (9 ± 5 vs. 13 ± 4%; p = .036, ω2 = 0.14) and the pV̇O2 gain at end-exercise (11.6 ± 0.6 vs. 12.4 ± 0.7 mL·min−1·W−1; p < .001, ω2 = 0.42) were observed. These data indicate that the control of oxidative phosphorylation in response to heavy-intensity cycling exercise is age-dependent in teenage boys.

V˙o 2 and heart rate kinetics in cycling: transitions from an elevated baseline

2001 ◽  
Vol 90 (6) ◽  
pp. 2081-2087 ◽  
Author(s):  
S. E. Bearden ◽  
R. J. Moffatt
Keyword(s):  
Heart Rate ◽  
Base Excess ◽  
Slow Component ◽  
Lactate Concentration ◽  
Fast Component ◽  
Square Wave ◽  
Mean Response Time ◽  
Rate Kinetics ◽  
Component Amplitude ◽  
Heart Rate Kinetics

The purpose of this study was to examine oxygen consumption (V˙o 2) and heart rate kinetics during moderate and repeated bouts of heavy square-wave cycling from an exercising baseline. Eight healthy, male volunteers performed square-wave bouts of leg ergometry above and below the gas exchange threshold separated by recovery cycling at 35%V˙o 2 peak.V˙o 2 and heart rate kinetics were modeled, after removal of phase I data by use of a biphasic on-kinetics and monoexponential off-kinetics model. Fingertip capillary blood was sampled 45 s before each transition for base excess, HCO[Formula: see text] and lactate concentration, and pH. Base excess and HCO[Formula: see text] concentration were significantly lower, whereas lactate concentration and pH were not different before the second bout. The results confirm earlier reports of a smaller mean response time in the second heavy bout. This was the result of a significantly greater fast-component amplitude and smaller slow-component amplitude with invariant fast-component time constant. A role for local oxygen delivery limitation in heavy exercise transitions with unloaded but not moderate baselines is presented.

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