Oxygen uptake and cardiac output at rest and during exercise after surgery for coarctation of the aorta.
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Abstract:
Oxygen uptake and cardiac output at rest and during exercise were studied in 19 men operated on for coarctation of the aorta during childhood. Their aerobic capacity and their maximal values for cardiac output, stroke volume and arteriovenous oxygen difference were normal. No differences were found regarding these variables between hypertensive and normotensive subjects. Thus, there was no sign of failure of the left ventricle even in patients with high blood pressure during exercise. Whether the normal arteriovenous oxygen difference indicates a normal distribution of the cardiac output cannot be settled from the present data.Keywords:
Arteriovenous oxygen difference
Rest (music)
Aerobic Exercise
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The purpose of this study was to examine the relationships between the central cardiovascular variables (cardiac output, stroke volume and heart rate) and oxygen uptake (VO2) during continuous, incremental cycle exercise to maximal aerobic capacity (VO2max).Twenty-one moderately to highly trained males (n=19) and females (n=2) participated in the study. A baseline maximal exercise test was performed to measure VO2max. Following the initial VO2max test, cardiac output was measured (CO2 rebreathing technique) at rest and 3 times during each of 4 exercise trials (2 submaximal tests to 90% VO2max and 2 maximal tests). Stroke volume and arteriovenous O2 difference were calculated using standard equations.Significant non-linear relationships were found between all central cardiovascular variables and VO2 (P<0.01). A plateau in cardiac output at VO2max was identified in 3 subjects. Stroke volume plateaued at an average of 37+/-12.5% of VO2max in 18 subjects and increased continuously to VO2max in 3 subjects. The arteriovenous O2 difference progressively increased to VO2max in 17 subjects and revealed a plateau response in 4 subjects.Our data suggest that there is a significant non-linear relationship between the central cardiovascular variables and VO2 during incremental exercise to VO2max. Furthermore, depending on the person, VO2max may be limited by cardiac output (evidence of cardiac output[Q] plateau) or peripheral factors (continued increase in Q).
Incremental exercise
Aerobic Exercise
Arteriovenous oxygen difference
Exercise physiology
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An exaggerated exercise blood pressure response (EEBPR) may be associated with an increased risk of hypertension. We hypothesized that aerobic exercise training can decrease EEBPR and the risk for hypertension by decreasing arterial resistance. We studied the effects of aerobic training on the submaximal exercise blood pressure (BP) of eight normotensive young adult African-American men with an EEBPR. Subjects were trained on a stationary bicycle at an intensity of 70% peak oxygen uptake (VO 2peak ), for 30 min, three times per week, for 8 weeks. BP, heart rate, cardiac output (CO), stroke volume (SV) and total peripheral vascular resistance (TPR) were measured at rest and during submaximal exercise at a work intensity of 50% VO 2peak. Significance of the training effects were evaluated by comparing the pre- and post-training measures ( t -test, p < 0.05). A 15% post-training increase in VO 2peak (34.6 - 1.4 to 40 - 1.4 ml/kg/min) and a 9.5 ml post-training increase in mean resting stroke volume were found. A 16.2 mmHg decrement in mean systolic BP, an 11.5 mmHg decrement in mean diastolic BP, a 120 dyne/s/cm 5 decrement in TPR and a 1.2 l/min increase in CO were detected during the posttraining submaximal exercise tests. These results suggest that reductions in TPR may attenuate the EEBPR of normotensive African-American males following an 8-week training regimen of stationary bicycling at 70% VO 2peak . Aerobic exercise training may, therefore, reduce the risk of hypertension in normotensive African-American males by the mechanism of a reduction in TPR. Because of the limited number of subjects, the results of this study should be interpreted cautiously pending confirmation by a larger controlled trial.
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High aerobic intensity interval training at 90-95% of maximal heart rate is more effective than continuous training with low to moderate intensity in improving maximal oxygen uptake in healthy young men. Maximal cardiac stroke volume was improved to a similar extent in high aerobic intensity interval training only. It is concluded that high aerobic intensity endurance training is significantly more effective than isocaloric training at lactate threshold (85% of maximal heart rate) or 70% of maximal heart rate, in improving maximal oxygen uptake and cardiac stroke volume. Improvements in maximal oxygen uptake corresponded with changes in stroke volume, indicating a close link between the two.High aerobic intensity interval training at 85-95% of peak heart rate significantly improves peak cardiac stroke volume and resting left ventricular ejection fraction in coronary artery disease patients. High aerobic intensity interval training improves peak cardiac stroke volume and left ventricular ejection fraction in coronary artery disease patients due to increased myocardial contractility and enhanced left ventricular systolic performance.Hyperoxic high aerobic intensity interval training at 85-95% of peak heart rate gave no additional effect over normoxic high aerobic intensity interval training in coronary artery disease patients. Hyperoxic training improves VO2peak and peak stroke volume to the same extent as ambient air training in stable coronary artery disease patients with mild to moderate coronary ischemia. As acute hyperoxia did not increase VO2peak it is concluded that the coronary artery disease patients showed peripheral oxygen limitations in VO2peak both before and after 10 weeks of hyperoxic training. Hyperoxic training may thereby represent no increase in cardiovascular shear stress.Maximal leg press exercise focusing on few repetitions with heavy loads and maximal concentric contractions improves maximal strength, rate of force developments and walking mechanical efficiency in coronary artery disease patients through a minimal exercise effort. Improved muscular strength and rate of force development translates into improved walking mechanical efficiency returning the patients work efficiency to the levels of healthy age matched subjects.
Hyperoxia
Aerobic Exercise
Interval training
Stroke
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Coarctation of the aorta is characterized by a high blood pressure in the upper part of the body and a decreased blood pressure in the lower part. Without surgery it leads to an increased mortality from hypertensive manifestations. However, even after surgery 20--25 per cent of these patients are reported to have a persistent hypertension. Moreover, an increased cardiovascular mortality has been reported. The aim of the present investigations was to study the long-term results after coarctectomy with special emphasis on reactions to hard muscular work and to study some of the possible mechanisms behind this persistent hypertension. Nineteen men aged 16--28 years, operated upon for coarctation of the aorta at an average age of 10 years (range 6--16 years), were investigated 10--11 years after surgery with respect to cardiac and pulmonary function, the state of the vessels and muscle metabolism. Lung function and the intrapulmonary gas exchange were normal, as was the maximal aerobic work capacity. Cardiac output and stroke volume and the arterio-venous oxygen difference were also normal, even during maximal exercise. More than half of the group had a systolic hypertension, both at rest and during exercise, in the upper part of the body, while the diastolic pressure was generally normal. A systolic blood-pressure gradient between the arm and the leg was observed and its was increased during exercise. Corresponding differences in the mean and diastolic pressures were also found during exercise. An increased muscle-lactate concentration in the leg and an increased muscle/blood lactate quotient during exercise indicated a somewhat impaired blood-flow to the leg muscle. The systemic vascular resistance in the right hand during maximal vasodilation was increased much more than the blood-presssure elevation indicated, while the baroreflex sensitivity was adequate. The findings favour early operation for coarctation of the aorta and indicate the necessity of thorough, and probably lifelong, follow-up of these patients. Moreover, blood pressure, either measured at rest or measured during exercise, cannot be used as a measure of the anatomical result after surgery. Key-words: Baroreflex sensitivity, cardiac output, coarctatio aorte, exercise test, hypertension, intra-arterial blood pressure, lung volumes, muscle metabolism, oxygen uptake, peripheral resistance, pulmonary gas exchange.
Venous return curve
Aerobic Exercise
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THE mechanisms of adaptation of the left ventricle to the demands of muscular exercise have intrigued cardiovascular physiologists for many years. Although highly complex, these adaptive mechanisms are more and more susceptible to analysis and quantification. In this presentation I will attempt to identify some of the individual factors which appear to be important in the response of the left ventricle to exercise, beginning with data obtained from experiments on conscious normal male subjects and proceeding to experiments performed on dog preparations in which individual factors were controlled and analyzed. The changes in oxygen intake, cardiac output, estimated arteriovenous oxygen difference, pulse rate and estimated mean stroke volume were determined in 15 normal male subjects during rest in the standing position and during treadmill exercise at the maximal oxygen intake level. Oxygen intake was obtained from the volume and composition of expired air, cardiac output by the dye dilution technique, and pulse rate from the electrocardiogram. Estimated arteriovenous oxygen difference was obtained by dividing the oxygen intake by the cardiac output (Fick principle) and estimated mean stroke volume by dividing the cardiac output by the heart rate. The data are shown in Figure 1. Oxygen intake increased from a mean value of 0.34 at rest to a maximal value of 3.22 L./min. The corresponding mean values for cardiac output were 5.4 and 23.4 L./min. and for arteriovenous oxygen difference were 6.5 and 14.3 ml./100 ml. Thus, as oxygen intake increased 9.5 times, the cardiac output increased 4.3 times and the arterio venous oxygen difference 2.2 times.
Fick principle
Arteriovenous oxygen difference
Oxygen pulse
Treadmill
End-systolic volume
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Aerobic training (AT) and circuit weight training (CWT) improve peak oxygen uptake (VO(2)peak). During CWT the circulatory system is exposed to higher pressure, which could induce left ventricle morphological adaptations, possibly distinct from those derived from aerobic training.To compare the effects of aerobic training and CWT upon morphological and functional cardiac adaptations detected by magnetic resonance imaging.Twenty healthy sedentary individuals were randomly assigned to participate in a 12-week programme of aerobic training (n = 6), CWR (n = 7) or no intervention (n = 7, controls). Training programmes consisted of 36 sessions, 35 min each, 3 times per week, at 70% of maximal heart rate, and CWT included series of resistance exercises performed at 60% of 1 maximal repetition. Cardiopulmonary exercise testing and cardiac magnetic resonance imaging were performed before and after the intervention.There was a similar improvement in VO(2)peak following aerobic training (mean (SD) increment: 12 (4)%) and CWT (12 (4)%), while there was no change in the control group. Aerobic training (12 (6)%) and CWT (16 (5)%) improved strength in the lower limbs, and only CWT resulted in improvement of 13 (4)% in the strength of the upper limbs. However, there were no detectable changes in left ventricular mass, end-diastolic volume, stroke volume or ejection fraction.In previously sedentary individuals, short-term CWT and aerobic training induce similar improvement in functional capacity without any adaptation in cardiac morphology detectable by cardiac magnetic resonance imaging.
Aerobic Exercise
Oxygen pulse
Continuous training
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AIM:
The purpose of this study was to examine the relationships between the central cardiovascular variables (cardiac output, stroke volume and heart rate) and oxygen uptake (VO2) during continuous, incremental cycle exercise to maximal aerobic capacity (VO2max).
METHODS:
Twenty-one moderately to highly trained males (n=19) and females (n=2) participated in the study. A baseline maximal exercise test was performed to measure VO2max. Following the initial VO2max test, cardiac output was measured (CO2 rebreathing technique) at rest and 3 times during each of 4 exercise trials (2 submaximal tests to 90% VO2max and 2 maximal tests). Stroke volume and arteriovenous O2 difference were calculated using standard equations.
RESULTS:
Significant non-linear relationships were found between all central cardiovascular variables and VO2 (P<0.01). A plateau in cardiac output at VO2max was identified in 3 subjects. Stroke volume plateaued at an average of 37+/-12.5% of VO2max in 18 subjects and increased continuously to VO2max in 3 subjects. The arteriovenous O2 difference progressively increased to VO2max in 17 subjects and revealed a plateau response in 4 subjects.
CONCLUSIONS:
Our data suggest that there is a significant non-linear relationship between the central cardiovascular variables and VO2 during incremental exercise to VO2max. Furthermore, depending on the person, VO2max may be limited by cardiac output (evidence of cardiac output[Q] plateau) or peripheral factors (continued increase in Q).
Arteriovenous oxygen difference
Incremental exercise
Aerobic Exercise
Cycling
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Aerobic capacity
Aerobic Exercise
Exercise intolerance
Arteriovenous oxygen difference
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The aim of this study was to investigate the character of changes in cardiac structure and function among elite judoists due to long-term judo practice.A group of male (N = 20, average age: 22.1) and female (N = 15, average age: 19.4) athletes practising judo for about 10 years was subjected to echocardiographic tests carried out during rest (aorta diameter [AoD], diastolic dimension of the left ventricle [Dd], thickness of the interventricular septum [IVST], the thickness of the posterior wall of the left ventricle [LVPWT]), and to measurement of cardiovascular system's action parameters (heart rate [HR], stroke volume [SV], cardiac output [Q], blood pressure [BP]). Moreover, control non trained subjects were also studied, women (N = 30, average age: 19.1) and men (N = 30, average age: 21.4). In order to determine aerobic efficiency, the authors measured the maximal oxygen uptake (VO2max) using the direct method. The anaerobic capacity was estimated on the basis of the maximal anaerobic power, and the volume of the performed work was calculated by means of the 30s Wingate test.Echocardiographic test values imply that changes in heart morphology induced by long term judo training, such as increase diastolic dimension of the left ventricle, thickness of the interventricular septum and left ventricular posterior wall, resemble more the changes observed in endurance athletes than changes observed in strength athletes.The obtained data indicated that judo training improves both aerobic and anerobic performance and these changes were associated with changes in heart structure and function as compared to non trained control.
Interventricular septum
Wingate test
Aerobic Exercise
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Oxygen uptake and cardiac output at rest and during exercise were studied in 19 men operated on for coarctation of the aorta during childhood. Their aerobic capacity and their maximal values for cardiac output, stroke volume and arteriovenous oxygen difference were normal. No differences were found regarding these variables between hypertensive and normotensive subjects. Thus, there was no sign of failure of the left ventricle even in patients with high blood pressure during exercise. Whether the normal arteriovenous oxygen difference indicates a normal distribution of the cardiac output cannot be settled from the present data.
Arteriovenous oxygen difference
Rest (music)
Aerobic Exercise
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Citations (6)