Oxygen uptake kinetics in cardiac transplant recipients

1994 ◽  
Vol 77 (4) ◽  
pp. 1935-1940 ◽  
Author(s):  
D. H. Paterson ◽  
D. A. Cunningham ◽  
J. G. Pickering ◽  
M. A. Babcock ◽  
D. R. Boughner
Keyword(s):  
Heart Rate ◽  
Gas Exchange ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Cardiac Transplant ◽  
O2 Uptake ◽  
Square Wave ◽  
Forcing Function ◽  
Slow Heart Rate ◽  
O2 Delivery

Our purpose was to examine the gas exchange response to exercise in heart transplant (HT) patients and to characterize the O2 uptake kinetics (tau VO2) during successive square-wave on-transients from loadless cycling to moderate exercise. We hypothesized that with a slow heart rate response (and O2 transport limitation) O2 kinetics would be slowed but that with a repeated exercise initiated while the heart rate remained elevated the tau VO2 would be faster. Six male HT patients performed two ramp-function tests to determine peak O2 uptake (1.32 +/- 0.23 l/min) and ventilation threshold (1.02 +/- 0.16 l/min). Patients subsequently completed two repeats of a square-wave forcing function and repeated this on 2 days. Alveolar gas exchange was measured breath by breath. A monoexponential fit of signal-averaged data of the first exercise on-transient (between days) yielded a significantly slower tau VO2 in HT subjects than in healthy men (mean age 47 yr; n = 8) (77 +/- 26 vs. 45 +/- 4 s). With successive exercise (2nd transition) initiated while HR remained elevated the tau VO2 of HT patients was 46 +/- 17 s. The faster O2 kinetics of the second transition suggests that O2 delivery was enhanced and therefore that the tau VO2 may reflect bioenergetic processes controlling the rate of oxidative metabolism.

The Inter-relationships Of Analysis Procedures In The Assessment Of Oxygen-uptake-kinetics Across PRBS And Square-wave Protocols

2005 ◽  
Vol 37 (Supplement) ◽  
pp. S447-S448
Author(s):  
Andrew M. Edwards ◽  
David Claxton ◽  
Carlton Cooke ◽  
Mary Fysh ◽  
Carl Wells
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Square Wave

Effects of beta-adrenergic blockade on ventilation and gas exchange during exercise in humans

1983 ◽  
Vol 54 (5) ◽  
pp. 1306-1313 ◽  
Author(s):  
E. S. Petersen ◽  
B. J. Whipp ◽  
J. A. Davis ◽  
D. J. Huntsman ◽  
H. V. Brown ◽  
...  
Keyword(s):  
Heart Rate ◽  
Gas Exchange ◽  
Time Constant ◽  
Minute Ventilation ◽  
Work Rate ◽  
Beta Blockade ◽  
Adrenergic Blockade ◽  
O2 Uptake ◽  
Beta Adrenergic ◽  
Co2 Partial Pressure

The effects of beta-adrenergic blockade induced by intravenous propranolol hydrochloride (0.2 mg/kg) on ventilatory and gas exchange responses to exercise were studied during tests in which the work rate was either increased progressively or maintained at a constant load in six healthy young male subjects. Heart rate during exercise decreased by about 20% and cardiac output, as estimated by a modification of the method of Kim et al. (J. Appl. Physiol. 21: 1338–1344, 1966), by about 15%. The relation between work rate and O2 uptake (VO2) was unaffected by propranolol, whereas maximal O2 uptake (VO2max) decreased by 5% and the anaerobic threshold, estimated noninvasively, was lowered by 23%. The relations between CO2 output (VCO2) and end-tidal CO2 partial pressure (PCO2) and between VCO2 and minute ventilation (VE) were both unaffected. The time constants for changes of VO2, VCO2, and VE during on-transients from unloaded pedaling to either a moderate (ca. 50% VO2max) or a heavy (ca. 67% VO2max) work rate in the control studies were in agreement with previously reported values, i.e., 42, 60, and 69 s, respectively. beta-Blockade was associated with a significantly increased time constant for VO2 of 61 s but with less consistent and insignificant changes for VCO2 and VE. There was a small but significant increase of the time constant for heart rate from 40 to 45 s. It is concluded that propranolol exerts its primary influence during exercise on the cardiovascular system without any discernible effect on ventilatory control.

Effect of Various Intensities of Short-Term Interval Training on Oxygen Uptake Kinetics

2016 ◽  
Author(s):  
Alex Green
Keyword(s):  
Interval Training ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Moderate Intensity ◽  
Metabolic Demand ◽  
O2 Uptake ◽  
O2 Uptake Kinetics ◽  
Optimal Intensity ◽  
Minute Duration ◽  
High Intensity Interval

Oxygen (O2) uptake kinetics reflect the rate at which an individual’s oxygen consumption (VO2) changes to meet a new metabolic demand, such as an increase or decrease in exercise intensity. O2 uptake kinetics can indicate cardiovascular and metabolic fitness and are described by the time variable, τ (tau), of the exponential equation describing the change in VO2. With training τ decreases, indicating a more rapid increase in VO2 to meet the new metabolic demand. Interval training at supramaximal (>100% VO2max) intensities has been shown to elicit similar improvements in O2 uptake kinetics to traditional endurance training. This study looked to determine the optimal intensity of interval training for eliciting improvements in O2 uptake kinetics. Fifteen recreationally active individuals (males: n=9, age = 23.3±3.3 years, VO2max = 44.2±6.5 ml O2•min-1•kg-1; females: n=6, age = 21.5±0.7 years, VO2max = 39.7±5.4 ml O2•min-1•kg-1) participated in 12 training sessions over 4 weeks. To measure O2 uptake kinetics subjects completed three step transitions from loadless (~25W) to low work-rate (~80W) cycling, prior and following training. Each subject was randomly assigned to one of three intensities - high-intensity interval training (HIIT ~120% VO2max), moderate-intensity interval training (MIIT ~90% VO2max), and low-intensity interval training (LIIT ~65% VO2max). Each session consisted of 8-12 intervals of 1-minute duration with 1-minute recovery on a stationary bicycle at the prescribed relative intensity. No significant differences between groups were observed in changes in τ (Δτ: LIIT: 3.1±8.3s; MIIT: -0.59±12.4s; HIIT: 6.2±6.0s).

The Inter-relationships Of Analysis Procedures In The Assessment Of Oxygen-uptake-kinetics Across PRBS And Square-wave Protocols

2005 ◽  
Vol 37 (Supplement) ◽  
pp. S447???S448
Author(s):  
Andrew M. Edwards ◽  
David Claxton ◽  
Carlton Cooke ◽  
Mary Fysh ◽  
Carl Wells
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Square Wave

scholarly journals Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

2012 ◽  
Vol 37 (4) ◽  
pp. 599-609 ◽  
Author(s):  
Oscar MacAnaney ◽  
Donal O’Shea ◽  
Stuart A. Warmington ◽  
Simon Green ◽  
Mikel Egaña
Keyword(s):  
Type 2 Diabetes ◽  
Heart Rate ◽  
Oxygen Uptake ◽  
Ventilatory Threshold ◽  
Constant Load ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Supervised Exercise ◽  
Rate Kinetics

Supervised exercise (SE) in patients with type 2 diabetes improves oxygen uptake kinetics at the onset of exercise. Maintenance of these improvements, however, has not been examined when supervision is removed. We explored if potential improvements in oxygen uptake kinetics following a 12-week SE that combined aerobic and resistance training were maintained after a subsequent 12-week unsupervised exercise (UE). The involvement of cardiac output (CO) in these improvements was also tested. Nineteen volunteers with type 2 diabetes were recruited. Oxygen uptake kinetics and CO (inert gas rebreathing) responses to constant-load cycling at 50% ventilatory threshold (VT), 80% VT, and mid-point between VT and peak workload (50% Δ) were examined at baseline (on 2 occasions) and following each 12-week training period. Participants decided to exercise at a local gymnasium during the UE. Thirteen subjects completed all the interventions. The time constant of phase 2 of oxygen uptake was significantly faster (p < 0.05) post-SE and post-UE compared with baseline at 50% VT (17.3 ± 10.7 s and 17.5 ± 5.9 s vs. 29.9 ± 10.7 s), 80% VT (18.9 ± 4.7 and 20.9 ± 8.4 vs. 34.3 ± 12.7s), and 50% Δ (20.4 ± 8.2 s and 20.2 ± 6.0 s vs. 27.6 ± 3.7 s). SE also induced faster heart rate kinetics at all 3 intensities and a larger increase in CO at 30 s in relation to 240 s at 80% VT; and these responses were maintained post-UE. Unsupervised exercise maintained benefits in oxygen uptake kinetics obtained during a supervised exercise in subjects with diabetes, and these benefits were associated with a faster dynamic response of heart rate after training.

Dynamics of ventilation, heart rate, and gas exchange: sinusoidal and impulse work loads in man

1980 ◽  
Vol 48 (2) ◽  
pp. 289-301 ◽  
Author(s):  
H. K. Bakker ◽  
R. S. Struikenkamp ◽  
G. A. De Vries
Keyword(s):  
Heart Rate ◽  
Gas Exchange ◽  
Work Load ◽  
Sine Wave ◽  
Bicycle Ergometer ◽  
Fat Free Mass ◽  
Co2 Production ◽  
O2 Uptake ◽  
Impulse Frequency ◽  
Frequency Responses

Dynamic characteristics of ventilation, heart rate, and gas exchange in response to sinusoidally varying work loads were analyzed in four male subjects, exercising in the upright position on a bicycle ergometer. Mean work-load and sinusoidal amplitude were about 1.5 and 0.9 W/kg, fat-free mass), respectively. Seven different frequencies were used, the periods ranging from 12 to 0.75 min. To further investigate the linearity of the variables under study, 10-s impulse loads were also applied to three of the four subjects. Harmonic analysis of the sine-wave data and comparison of the sine-wave fundamental responses with the impulse frequency responses showed that only O2 uptake behaves in a linear fashion. Ventilation and CO2 production showed quasi- to nonlinear behaviors, whereas the responses of heart rate and alveolar partial pressures were clearly dependent on the type of forcing used. By means of mathematical parameter identification techniques, it was found that the individual frequency responses of O2 uptake could be almost completely described by a four-parameter transfer function with parameter values showing second-order underdamped to critically damped dynamics.

Effects of acute hypoxia on the oxygen uptake kinetics of older adults during cycling exercise

2012 ◽  
Vol 37 (4) ◽  
pp. 744-752 ◽  
Author(s):  
Livio Zerbini ◽  
Alfredo Brighenti ◽  
Barbara Pellegrini ◽  
Lorenzo Bortolan ◽  
Tommaso Antonetti ◽  
...  
Keyword(s):  
Older Adults ◽  
Oxygen Uptake ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Incremental Test ◽  
Square Wave

Pulmonary oxygen uptake, heart rate (HR), and deoxyhemoglobin (HHb) kinetics were studied in a group of older adults exercising in hypoxic conditions. Fourteen healthy older adults (aged 66 ± 6 years) performed 4 exercise sessions that consisted of (i) an incremental test to exhaustion on a cycloergometer while breathing normoxic room air (fractional inspired oxygen (FiO2) = 20.9% O2); (ii) an incremental test to exhaustion on a cycloergometer while breathing hypoxic room air (FiO2 = 15% O2); (iii) 3 repeated square wave cycling exercises at moderate intensity while breathing normoxic room air; and (iv) 3 repeated square wave cycling exercises at moderate intensity while breathing hypoxic room air. During all exercise sessions, pulmonary gas exchange was measured breath-by-breath; HHb was determined on the vastus lateralis muscle by near-infrared spectroscopy; and HR was collected beat-by-beat. The pulomary oxygen uptake kinetics became slower in hypoxia (31 ± 9 s) than in normoxia (27 ± 7 s) because of an increased mismatching between O2 delivery to O2 utilization at the level of the muscle. The HR and HHb kinetics did not change between hypoxia and normoxia,

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