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PubMed1999

Change point in VCO2 during incremental exercise test: a new method for assessment of human exercise tolerance.

The main purpose of this study was to present a new method to determine the level of power output (PO) at which VCO2 during incremental exercise test (IT) begins to rise non-linearly in relation to power output (PO) - the change point in VCO2 (CP-VCO2). Twenty-two healthy non-smoking men (mean +/- SD: age 22.0 +/- 0.9 years; body mass 74.5 +/- 7.5 kg; height 181 +/- 7 cm; VO2max 3.753 +/- 0.335 l min-1) performed an IT on a cycloergometer. The IT started at a PO of 30 W, followed by gradual increases of 30 W every 3 min. Antecubital venous blood samples were taken at the end of each step and analysed for plasma lactate concentration [La]pl, blood PO2, PCO2 [HCO3-]b and [H+]b. In the detection of the change-point VCO2 (CP-VCO2), a two-phase model was assumed for the 'third-minute-data' of each step of the test. In the first phase, a linear relationship between VCO2 and PO was assumed, whereas in the second, an additional increase in VCO2 was allowed, above the values expected from the linear model. The PO at which the first phase ends is called the change point in VCO2. The identification of the model consists of two steps: testing for the existence of the change point, and estimating its location. Both procedures are based on suitably normalized recursive residuals (see Zoladz et al. 1998a. Eur J Appl Physiol 78, 369-377). In the case of each of our subjects it was possible to detect the CP-VCO2 and the CP-VO2 as described in our model. The PO at the CP-VCO2 amounted to 134 +/- 42 W. The CP- VO2 was detected at 136 +/- 32 W, whereas the PO at the LT amounted to 128 +/- 30 W and corresponded to 49 +/- 11, 49 +/- 8 and 47 +/- 8.6% VO2max, respectively, for the CP-VCO2, CP-VO2 and the LT. The [La]pl at the CP-VCO2 (2.65 +/- 0.76 mmol L-1), at the CP-VO2 (2.53 +/- 0. 56 mmol L-1) and at the LT (2.25 +/- 0.49 mmol L-1) were already significantly higher (P < 0.01, Students t-test) than the value reached at rest (1.86 +/- 0.43 mmol L-1). Our study illustrates that the CP-VCO2 and the CP-VO2 occur at a very similar power output as the LT. We therefore postulate that the CP-VCO2 and the CP-VO2 be applied as an additional criterion to assess human exercise tolerance.

Adult↗
PubMed1975

Exercise tolerance after repair of tetralogy of Fallot.

Twelve patients who had undergone complete repair of tetralogy of Fallot at ages ranging from 8 to 27 years were studied for exercise tolerance several years later. Work performance ranged from 58 to 130% of that predicted. Increased physiological dead space and alveolar-arterial Po2 difference at exercise suggested pulmonary vascular disease, which was confirmed in 1 patient by pulmonary angiography. Excercise tolerance decreased with increasing age at time of repair, underlining the desirability of early corrective operation.

Acid-Base Equilibrium↗
PubMed1993

[Effect of treatment with indobufen on blood viscosity indices and exercise tolerance in patients with coronary disease].

The study included 20 patients aged from 50 to 65 years with stable coronary disease. In all patients exercise ECG test in Quinton moving track was performed before the treatment, and after one, three, and eight weeks of therapy. Besides that, before the treatment, and after each exercise, platelet aggregation, viscosity of whole blood and plasma, and filtration time of 1 ml of whole blood were evaluated. It was found that already after one week of treatment indobufen caused a decrease of platelet aggregation, reduction of viscosity of whole blood and plasma, and improvement of erythrocyte compliance which favourable effects increased with the continuation of the therapy up to eight weeks. At the same time as a result of eight weeks of treatment a significant improvement was achieved of exercise tolerance in the treated patients.

Adult↗
PubMed1986

Effect of bisoprolol on exercise tolerance in patients with coronary heart disease: placebo-controlled double-blind crossover study.

Twelve patients with stable angina pectoris due to coronary heart disease received single oral doses of 5, 10, and 20 mg bisoprolol in a placebo-controlled double-blind crossover study. A significant, dose-related increase in exercise tolerance in symptom-limited bicycle exercise tests performed 2.5 h after administration (p less than 0.05) was demonstrated. The dose-effect relationship was especially marked in reduction of heart rate, rate-pressure product, and ischemic ST-segment depression at the highest comparable workload (p less than 0.01). Compared with placebo, mean improvements in work performance (determined by the maximal workload attained, i.e., W X minutes) increased to 105% with 5 mg, to 122% with 10 mg, and to 131% with 20 mg bisoprolol. The lower incidence rate of exercise-induced symptoms of angina pectoris at an identical workload was marked at the 10- and 20-mg dose.

Adrenergic beta-Antagonists↗
PubMed1998

Exercise-based rehabilitation improves skeletal muscle capacity, exercise tolerance, and quality of life in both women and men with chronic heart failure.

BACKGROUND: Data of training effects in chronic heart failure patients are based on findings in men. The purpose of this study was to compare the effects of skeletal muscle endurance training between men and women with chronic heart failure. METHODS AND RESULTS: Twelve consecutive men (mean [+/- SD] age 58 +/- 9 years, left ventricular ejection fraction 29 +/- 9%) and 12 women (60 +/- 10 years, left ventricular ejection fraction 28 +/- 7%) with moderate, chronic heart failure stratified according to age and inclusion criteria were investigated at baseline and after 8 weeks of knee extensor endurance training. The activity of skeletal muscle citrate synthase and resting heart rate were similar in men and women at baseline and with training improved (P < .0001) similarly in both genders. Peak work rate (P < .0001), peak oxygen uptake (P < .001) and muscle strength (P < .05) at baseline were higher in men than in women. Training improved peak work rate (P < .0001) and muscle strength (P < .0001) similarly in both genders, while improvement in peak oxygen uptake was better in women (P < .001). The distance ambulated during 6 minutes was similar in both genders at baseline and increased after training more in men (P < .004). The overall and physical Sickness Impact Profile indicated similarly reduced health-related quality of life in men and women, while worse psychosocial quality of life was observed in men (P < .05). Both genders improved after exercise training in the overall, physical, and psychosocial Sickness Impact Profile (P < .01). CONCLUSIONS: Exercise-based rehabilitation improves skeletal muscle capacity, exercise tolerance, and the health-related quality of life in women as well as in men with moderate, chronic heart failure.

Aged↗
PubMed1993

Exercise tolerance in angina is improved by mivazerol--an alpha 2-adrenoceptor agonist.

In a double-blind, placebo-controlled, randomized trial of treadmill exercise tolerance in six patients with chronic stable angina, intravenous mivazerol 1 microgram, 2 micrograms, and 3 micrograms/kg increased the time to onset of angina by 39%, 48%, and 76%; the time to 1-mm ST depression by 36%, 76%, and 104%; and total exercise duration by 15%, 23%, and 30%, respectively. In a subsequent double-blind, placebo-controlled, randomized trial involving a further 12 patients, a single oral dose of mivazerol of 800 micrograms, 1200 micrograms, and 1600 micrograms increased the time to onset of angina by 4%, 11%, and 30%; the time to 1-mm ST depression by 33%, 43%, and 53%; and the total exercise duration by 10%, 18%, and 23%, respectively. Mivazerol is an imidazole derivative with agonist properties at the alpha 2-adrenoceptor and appears to be an effective antianginal. Mivazerol may improve exercise performance by attenuating the effects of exercise-induced sympathetic nervous system activity on the ischemic myocardium.

Administration, Oral↗
PubMed1976

Effects of practolol on exercise tolerance and cardiac haemodynamics and metabolism in patients with coronary artery disease.

Sixteen male patients with typical angina pectoris secondary to coronary atherosclerosis performed two daily standardized exercise tests during two consecutive days. Three hours before each exercise they received placebo or 400 mg practolol administered orally in double-blind fashion in order to complete a cross-over design. Practolol significantly prolonged the exercise duration by 30.6% and delayed the appearance time of ischaemic electrocardiographic changes by 67.7%. Maximal heart rate, systolic pressure, and pressure-rate product were also reduced after medication. In order to investigate further the effects of this beta blocking agent, myocardial function and metabolism at rest and during supine exercise were assessed in 12 male patients with coronary artery disease before and after practolol 30 mg, iv. At rest, practolol produced a decrease in tension-time index (18%), cardiac index (17%), heart rate (10%), and stroke index (7%). A significant reduction was also observed in resting stroke work index (14%) and systolic and mean aortic pressure (6%). Left ventricular end-diastolic pressure remained unchanged. During supine exercise, only time-tension index (12%), heart rate (12%), and cardiac index (10%) were significantly reduced after the beta blocking agent. Practolol did not significantly change the arterial glucose, lactate, inorganic phosphate, potassium, calcium, magnesium, pH, PCO2, or PO2. The beta blocking agent did not modify the myocardial extraction of any of these substrates at rest or during exercise. In the dosage used in both studies, practolol significantly improved the exercise tolerance and reduced the ischaemic manifestations. The efficacy of practolol in angina pectoris may result mostly from its ability to decrease heart rate and systolic pressure during exercise.

Adult↗
PubMed1990

Effects of verapamil and atenolol on exercise tolerance in 5,000 m cross-country running: a double-blind cross-over study in normal humans.

The effects on exercise tolerance of 7-day treatment with a calcium channel blocker, verapamil 160 mg twice daily (b.i.d.), and a beta 1-selective blocker, atenolol 50 mg b.i.d., were compared in 10 healthy and physically active young subjects in 5,000-m cross-country running at high intensity. The study was a double-blind cross-over trial. Comparison was made with a single-blind placebo as well. Performance time was measured every 1,000 m in seven 5,000-m runs, in which subjects were instructed to keep to a constant fatigue perception (Borg scale rating). Both drugs significantly (p = 0.001) increased the performance time over the first 1,000 m as compared with placebo. However, running time after 1,000, 2,000, and 3,000 m was prolonged significantly less (p less than 0.05) by verapamil than by atenolol. For the entire 5,000-m run, atenolol caused a significant increase (p = 0.001) in mean running time by 1 min 34 s (i.e., 7.5%; 95% confidence interval 48 s to 2 min 21 s) as compared with placebo, whereas verapamil caused no significant change (+46 s).

Adult↗
PubMed1989

Exercise tolerance in chronic obstructive pulmonary disease: importance of active and passive components of the ventilatory system.

We investigated which components of ventilatory function are related to exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. Physical characteristics, usual lung function, timing and neuromuscular components of ventilation were measured in 113 outpatients in whom FEV1/VC was less than 75% of the predicted value and exercise was limited by breathlessness. These variables were used to predict the maximum work load during progressive bicycle exercise. The prediction was obtained using a stepwise procedure in men and women separately. Among the variables selected, age, body weight, FEV1/VC, PImax, and P0.1/VT/TI accounted for 79% of the variability in maximum performance in men. The predictive model was statistically verified and was stable. The mean prediction error was 12 Watts. Among these variables, P0.1/VT/TI, PImax, and FEV1/VC were the main determinants of maximum work load (MWL). These results show that exercise limitation in COPD is related to impairment of both the active (inspiratory muscles) and passive (respiratory impedance) components of the ventilatory system. The same conclusions concerning passive components are proposed for women, despite a smaller population which prevented verification of the prediction.

Adult↗
PubMed1976

Aspirin therapy in angina pectoris: effects on platelet aggregation, exercise tolerance, and electrocardiographic manifestations of ischemia.

If altered platelet function contributes to poorly perfused zones of myocardium in patients with angina pectoris, then specific antiplatelet therapy might improve cardiovascular function and exercise performance. Exercise tolerance on a bicycle ergometer, heart rate-blood pressure product, and ischemic ECG changes at exercise end-point were compared before and during oral aspirin therapy (2.4 Gm. per day for 2 weeks) in 11 normal subjecs and in 11 patients with stable angina pectoris. Platelet aggregation threshold in response to ADP and epinephrine was measured. Untreated patients had increased platelet aggregability when compared to normal subjects...

Adult↗
PubMed2003

Adjunctive sympathoplegic therapy to ACE inhibition in Blacks with congestive heart failure: a comparison of alpha-1 with beta-1 blockade on exercise tolerance and cardiac sympathovagal reflex activity.

OBJECTIVES: Congestive heart failure (CHF) is characterized by an initial compensatory, but subsequently deleterious, activation of both the renin-angiotensin (RAS) and the sympathetic nervous system (SNS). Incomplete suppression of the SNS may contribute to the residual mortality during optimal ACE inhibitor therapy in CHF. Carvedilol, a mixed alpha and beta-blocker with antioxidant properties, and other pure beta-adrenoceptor blockers reduce morbidity and mortality in Caucasians with CHF. However, beta-blocker monotherapy is of poor efficacy in Blacks with essential hypertension or in the treatment of glaucoma. The efficacy of beta-blockers in the treatment of African Americans with congestive heart failure is a controversial issue with conflicting findings. The aims of the present study were to examine and compare the cardiovascular, autonomic, and clinical effects of additional alpha-1, or beta-1 blockade in ACE-inhibitor treated Black patients with moderate to severe CHF. METHODS: Twenty-eight Nigerian patients with chronic CHF stabilized on digoxin and diuretics, were randomized to 3 groups of similar demographics according to a single blind, parallel group design. The patients were aged 53 +/- 6 years, and comprised 14 men and 14 women, with a mean cardiothoracic ratio of 0.66 +/- 0.03, and ejection fraction of 0.38 +/- 0.10, 60% hypertensive etiology. Group 1 patients received 5 mg enalapril alone, group 2 received 5 mg enalapril + 1 mg prazosin, and group 3 received 5 mg enalapril + 50 mg atenolol. All medication was taken daily for 4 weeks. Blood pressure, heart rate, pressure rate product, 6-minute walk test, NYHA class, and cardiac autonomic reflexes were measured at baseline and again at 2 and 4 weeks of treatment. Two-way repeated measures ANOVA, and a one-way ANOVA were used in data analysis. RESULTS: The 3 treatments caused significant (P<.001 ANOVA) and similar improvements for the NYHA class (-1.0 to -1.6), and increased the 6-minute distance covered (+130 m to +205 m). Although no treatment differences were observed, a trend suggesting a greater improvement with enalapril + atenolol became apparent. By the fourth week, the sympathoplegic treatments, enalapril + atenolol, and enalapril + prazosin, caused significant reductions in the pressure rate product (-3726 +/- 1885 mm Hg x beats/min; -3498 +/- 396 mm Hg beats/min, respectively), (compared to enalapril alone (-1349 +/- 894 mm Hg x beats/min) (P<.001 ANOVA). During the Valsalva maneuver, the phase IV bradycardia were significantly greater after treatment with enalapril + atenolol (944 +/- 66 msec) or with enalapril + prazosin (825 +/- 48 msec), compared to enalapril alone (760 +/- 45 msec) (P<.001 ANOVA). The phase II Valsalva tachycardia were similar between treatments. The respiratory sinus arrhythmia ratio increased significantly (P<.005 ANOVA) and equally on all treatments. However, the pressor and chronotropic responses to forearm isometric handgrip increased significantly on the enalapril + prazosin combination (P<.02), compared to the other treatments. CONCLUSIONS: Our findings demonstrated not only the safety of providing additional therapy with alpha-1 or beta-1 receptor blockade concurrent with ACE inhibition in Blacks with CHF, but also the resultant improvement in exercise tolerance and NYHA class. Compared to using ACE inhibition alone, the combined therapies caused a marked reduction in the pressure rate product, an index of myocardial oxygen consumption, and a greater enhancement of cardiac parasympathetic activity. Selective beta-1 blockade caused a greater enhancement of central baroreceptor vagal activity compared to alpha-1 blockade. Conversely, the pressor and chronotropic abnormalities during forearm isometric handgrip in CHF, were normalized by alpha-1, but not beta-1, blockade. Thus, the combined reflex cardiac vagal augmentation following selective beta-1 blockade, and the hemodynamic effects of alpha-1 antagonism with concurrent ACE inhibition, may be of major therapeutic and prognostic benefit in Blacks with non-ischemic (hypertensive) CHF stabilized on digoxin and diuretics.

Adrenergic alpha-Antagonists↗
PubMed1990

Hemodynamics and exercise tolerance after bisoprolol, nifedipine, and their combination in patients with angina pectoris.

The different mechanisms of action of beta-blockers and calcium antagonists could result in an additive therapeutic effect in patients with angina pectoris. Twenty-one male patients aged between 41 and 68 years and suffering from chronic stable angina pectoris and coronary artery disease confirmed by angiography took part in a randomized, double-blind study to examine the acute effect of 10 mg of bisoprolol, 20 mg of nifedipine, and a combination of the two drugs on hemodynamics at rest and during exercise [heart rate (HR), systolic blood pressure (SBP), rate-pressure product (RPP), cardiac index (CI), total peripheral resistance (TPR), and pulmonary capillary wedge pressure (PCP)], the behavior of the ST segment (ST), and exercise tolerance until occurrence of an ST-segment depression of 0.1 mV (W-ST01) and until onset of anginal pain (W-AP1). Following a baseline exercise test, 11 patients were given 10 mg of bisoprolol orally, whereas 10 patients received placebo. Two hours later, a second exercise test was carried out. All patients in both groups then received 20 mg of N orally. A third exercise test was performed 2 h later. On exercise, bisoprolol resulted in significant changes in HR (-16%), RPP (-22%), and CI (-16%), as well as in TPR (+ 13%); PCP was not significantly affected. Nifedipine led to significant changes in CI (+9%) and PCP (-34%). The effects of bisoprolol on HR and RPP and of nifedipine on PCP were retained in the combination. Competition was detectable as regards the opposing effects on CI and TPR. Measured by W-ST01 and ST, bisoprolol had a marked anti-ischemic effect, whereas that of nifedipine was distinctly less. There was an increase in effect after combination of the drugs (not significant). In patients with chronic angina pectoris due to coronary artery disease, bisoprolol and nifedipine had different hemodynamic profiles after acute administration; when the two drugs were combined, these effects were partly intensified and partly canceled out. There was a tendency for the effect of bisoprolol to be intensified by nifedipine in the combination. The combination of bisoprolol and nifedipine was well tolerated in the doses selected.

Adrenergic beta-Antagonists↗
PubMed1981

Angina pectoris: effects of lidoflazine on exercise tolerance and chest pain.

In a double-blind study involving 24 patients, treatment with lidoflazine in comparison with placebo was associated with a significant improvement in exercise tolerance; the median increase in work performed was 62 percent. This increase was significant at the 6th week of assessment. Ten patients were followed up for a further 2 years. Lidoflazine therapy was associated with a significant improvement in work done over that period. Lidoflazine was well tolerated and apparent adverse effects were minor.

Adult↗
PubMed1989

Experience with activity sensing rate responsive ventricular pacing. A study based upon assessment of exercise tolerance.

Fourteen patients (mean age 41 years) who received rate responsive activity sensing VVI pacemakers were studied to evaluate the relationship between the rate response and exercise tolerance by analysing the symptom limited maximum treadmill time both during fixed rate VVI oacubg abd dyrubg VVI + activity mode pacing (RRP). The proper functioning of RRP mode was confirmed by Holter monitoring in all. The indications for pacing were, sino-atrial block with high grade AV block, tachybrady syndrome, atrial fibrillation with complete heart block, congenital complete heart block and persistent slow junctional rhythm. Basic rate was programmed to 70 PPM in both pacing modes; rate response and activity threshold were programmed to 5 and medium respectively. The order in which two pacing modes were tested was chosen randomly. The maximum treadmill time (MTT) was 25.4% longer in the RRP than in VVI mode with a mean of 11.4 minutes in RRP and 8.5 mins in VVI(p less than 0.01). for the subgroup of patients who demonstrated paced only rhythm the average increase in MTT was 31.4% with a mean of 11.8 minutes in RRP and 8.1 mins in VVI (p less than 0.01). Five patients who showed intermittent spontaneous rhythm, increased their average MTT by 22.3% with a mean of 11.2 minutes in RRP and 8.7 mins in VVI mode (p less than 0.05). During RRP a significance positive correlationship was seen between MTT and the increase in heart rate (N = 14, r = 0.85, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Influence of debrisoquine oxidation phenotype on exercise tolerance and subjective fatigue after metoprolol and atenolol in healthy subjects.

1. The effects of single doses of metoprolol 50 mg, metoprolol 100 mg and atenolol 100 mg on exercise tolerance were compared with placebo in a double-blind random cross-over study in 12 healthy subjects. Nine subjects were extensive metabolisers of debrisoquine, and three were poor metabolisers. 2. Three hours after dosing beta-adrenoceptor blocker treatments significantly reduced exercise heart rate, prolonged time to complete exercise, and increased subjective fatigue measured by visual analogue scale. 3. Scores for subjective fatigue did not correlate with reduction in exercise heart rate or prolongation of exercise time. Exercise time prolongation was weakly but not significantly correlated with exercise heart rate reduction. 4. When compared with placebo, prolongation of exercise time and increased fatigue with metoprolol were not significantly related to debrisoquine oxidation phenotype or to the debrisoquine/4-hydroxydebrisoquine (D/4OH-D) ratio. 5. When metoprolol responses were compared with those for atenolol, changes in exercise time and fatigue scores were significantly related to oxidation phenotype. For metoprolol 100 mg, poor metabolisers required 20.8 s longer to complete exercise (P less than 0.05) and had higher fatigue scores by 78% (P less than 0.05) as compared with extensive metabolisers.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗