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PubMed1987

Effects of pre-exercise carbohydrate feedings on muscle glycogen use during exercise in well-trained runners.

The purpose of this study was to examine the effects of pre-exercise glucose and fructose feedings on muscle glycogen utilization during exercise in six well-trained runners (VO2max = 68.2 +/- 3.4 ml X kg-1 X min-1). On three separate occasions, the runners performed a 30 min treadmill run at 70% VO2max. Thirty minutes prior to exercise each runner ingested 75 g of glucose (trial G), 75 g of fructose (trial F) or 150 ml of a sweetened placebo (trial C). During exercise, no differences were observed between any of the trials for oxygen uptake, heart rate or perceived exertion. Serum glucose levels were elevated as a result of the glucose feeding (P less than 0.05) reaching peak levels at 30 min post-feeding (7.90 +/- 0.24 mmol X l-1). With the onset of exercise, glucose levels dropped to a low of 5.89 +/- 0.85 mmol X l-1 at 15 min of exercise in trial G. Serum glucose levels in trials F and C averaged 6.21 +/- 0.31 mmol X l-1 and 5.95 +/- 0.23 mmol X l-1 respectively, and were not significantly different (P less than 0.05). There were also no differences in serum glucose levels between any of the trials at 15 and 30 min of exercise.

Adult↗

PubMed1984

The cardiokymography exercise test compared to the thallium-201 perfusion exercise test in the diagnosis of coronary artery disease.

To determine the usefulness of exercise cardiokymography (CKG) compared to thallium-201 perfusion scanning in the diagnosis of coronary artery disease (CAD), 179 patients with a mean age of 54 +/- 10 years (73% men) were studied. Previously documented CAD was present in 73 patients (41%); 13 (7%) were asymptomatic and 93 (53%) had chest pain syndrome. Exercise stress testing, CKG, and thallium-201 perfusion scanning were independently correlated with coronary angiographic data. Treadmill exercise stress test alone without CKG had a sensitivity of 68% and specificity of 62%. CKG showed a sensitivity of 76% and a specificity of 90%, and easily interpreted cardiokymograms were obtained in 78% of patients studied. Thallium-201 scans had a sensitivity of 79% and a specificity of 88%. However, when the CKG and treadmill exercise test results were concordant (both positive or both negative), the CKG exercise test had a sensitivity of 87% and specificity of 100%. Thus, when the CKG and exercise test results are concordant, the sensitivity and specificity are equal to or better than thallium-201 perfusion scanning for the prediction of CAD. Since CKG is an inexpensive and noninvasive test, its adjunctive use with routine exercise stress testing may be of great value.

Adolescent↗

PubMed1991

Submaximal, but not maximal, exercise testing detects differences in the effects of beta-blockers during treadmill exercise: a study of celiprolol and atenolol. II.

Celiprolol is a new-generation beta-blocker with ancillary properties that include partial beta 2-agonism and direct vasodilating activity. The effects of atenolol and celiprolol on maximal exercise capacity and on both respiratory variables and subjective indices of breathlessness and fatigue during submaximal exercise were compared in a placebo-controlled crossover study of 12 trained volunteers. Both atenolol and celiprolol equally and significantly reduced exercise capacity and maximal oxygen consumption. During constant submaximal exercise at 70% maximal oxygen uptake, however, differences emerged between the two beta-blockers. Atenolol was associated with a significantly higher minute ventilation than placebo. In contrast, values for minute ventilation and respiratory exchange ratio with celiprolol were similar to values with placebo. During the early stages of exercise, treatment with atenolol was also associated with higher scores for the subjective indices of breathlessness and fatigue. Thus submaximal exercise, which may be physiologically more relevant to the everyday activities of patients, may demonstrate potentially useful differences between drugs that are not seen during maximal exercise testing.

Adrenergic beta-Antagonists↗

PubMed1982

Hypercapnic ventilation during exercise: effects of exercise methods and inhalation techniques.

The effect of exercise on the ventilatory response to inhaled CO2 is uncertain because previous studies using different techniques have come to different conclusions. We undertook to resolve this problem by using multiple techniques and confining our study to a uniform level of mild exercise (VO2 = 10 ml/kg min). One group of subjects exercised on a treadmill and was tested with both rebreathing and steady-state CO2 methods. A second group exercised on a bicycle while using the rebreathing method. We found that the ventilatory response to CO2 was unchanged by mild exercise, regardless of the method used for CO2 inhalation or the technique used for exercise. These results indicate that under controlled conditions mild exercise does not produce any change in ventilatory sensitivity to CO2.

Adult↗

PubMed1994

Effects of short- and long-term carvedilol administration on rest and exercise hemodynamic variables, exercise capacity and clinical conditions in patients with idiopathic dilated cardiomyopathy.

OBJECTIVES: The study evaluated the effects of short- and long-term administration of carvedilol in patients with idiopathic dilated cardiomyopathy. BACKGROUND: Carvedilol is a beta-adrenergic blocking agent with vasodilator activity that might be well tolerated in patients with heart failure. METHODS: Forty patients with idiopathic dilated cardiomyopathy treated with digoxin, furosemide and angiotensin-converting enzyme inhibitors were randomized in a double-blind manner to receive either placebo or carvedilol. Right heart hemodynamic variables were evaluated up to 8 h after short-term drug administration and, on the next day, during cardiopulmonary exercise testing before and 3 h after drug ingestion. Placebo or carvedilol was added to standard therapy, starting with a dose of 6.25 mg twice a day with weekly increments up to the maximum of 25 mg twice a day. Patients were reevaluated after 4 months by cardiopulmonary exercise testing and measurement of right heart hemodynamic variables 12 h after last drug ingestion and 3 h after drug readministration. Left ventricular ejection fraction and volume, measured by equilibrium radionuclide ventriculography, quality of life and submaximal exercise duration were assessed before and after long-term therapy. RESULTS: Compared with placebo, carvedilol produced a short-term reduction in heart rate and pulmonary artery and pulmonary wedge pressures and, after long-term administration, increased both rest and peak exercise cardiac, stroke volume and stroke work indexes, with a further reduction in right atrial, pulmonary artery and pulmonary wedge pressures. Long-term carvedilol administration also improved rest left ventricular ejection fraction (from 20 +/- 7% to 30 +/- 12%, p < 0.001), submaximal exercise capacity, quality of life and New York Heart Association functional class. No baseline variable was predictive of the response to therapy. CONCLUSIONS: Short-term carvedilol administration reduces heart rate and mean pulmonary artery and pulmonary wedge pressures, whereas it improves both long-term rest and exercise left ventricular systolic function, reduces heart failure symptoms and improves submaximal exercise tolerance in patients with idiopathic cardiomyopathy.

Adrenergic beta-Antagonists↗

PubMed2002

Effects of propranolol and nitrates on exercise capacity, respiratory minute volume and capillary oxygen saturation during exercise in cirrhotic patients with portal hypertension.

A cross over study was performed in 16 cirrhotic patients with portal hypertension and oesophageal varices to assess the effects of propranolol and nitrates on the exercise capacity, respiratory minute volume and capillary oxygen saturation during exercise. All had normal peak expiratory flow rates, spirometry, chest X-ray, electrocardiography, ECHO cardiography, cardiac ejection fraction>55%, absent intra-pulmonary arterio-venous shunts (IPAVS) on contrast enhanced ECHO, and a haemoglobin>11 g/dl. Minute volume, capillary O(2) saturation and pulse rate, were measured during progressive exercise testing up to maximum exercise capacity. Testing was done on inclusion, after 1 month of treatment with propranolol (dose adequate for 25% reduction in resting pulse rate) and after another month of treatment with propranolol plus isosorbide dinitrate (ISDN). An age matched group of cirrhotics (n=9) (with no evidence of portal hypertension and had normal cardio respiratory functions as defined above) acted as controls. We observed a significant reduction in the minute volume at maximum exercise after both modes of treatment when compared to the pre-treatment values and the values of controls. There was a non-significant increase in capillary oxygen saturation. None of them had a reduction in exercise capacity after treatment. In conclusion, treatment with propranolol or a combination of propranolol and a nitrate dose not seem to impair exercise performance in patients who have hepatic cirrhosis with portal hypertension.

Journal Article↗

PubMed1985

Muscular exercise in type I-diabetics. II. Hormonal and metabolic responses to moderate exercise.

In Type I-diabetics metabolic response to exercise is largely determined by the availability of exogenous insulin. The aim of the present study was to assess the metabolic response to moderate exercise of 24 insulin-dependent (Type I-) diabetics treated by multiple subcutaneous injections of short acting insulin. Differences in insulin availability (hypo- [trial A] or hyperinsulinemia [trial B]) resulted from the different periods of time that had elapsed since the previous insulin injection, i.e., after 3 hours (trial A), and 1 hour (trial B). Bicycle ergometer tests at intensities up to 75% VO2max, were carried out with patients and controls. Plasma glucose, FFA, glycerol, alanine, growth hormone and glucagon levels were measured during a period of 85 min. In both trials, physical exertion did not have a significant statistical effect on the glucose concentration in the blood of hypo- and hyperinsulinemics. Surprisingly, despite the different insulin availabilities FFA, glycerol, alanine and glucagon concentrations were not statistically different in either trial and appear similar to those of healthy controls. A normal metabolic response to exercise can thus also be expected in Type I-diabetics, provided adequate insulin is available. When compared to controls, growth hormone concentrations were found to have increased during exercise. These experimental data strongly suggest the great necessity of adequate insulin availability in order to obtain normal metabolic responses to exercise in insulin-dependent diabetics. Despite certain degrees of hypo- or hyperinsulinemia, moderate exercise did not cause any marked metabolic derangements. This type of moderate exercise is therefore recommended for improving metabolic control in such patients.

Adult↗

PubMed1990

Post-exercise platelet activation--aggregation and release in relation to dynamic exercise.

Relatively scarce information is found on the period immediately following physical stress, with special reference to human platelet activity. This, in connection with earlier observations of an increase in platelet release products and hyperaggregability following surgical stress, has initiated the present study. We studied platelet function in eight healthy non-mediated volunteers during and 1 h after cycle exercise of submaximal intensity. ADP-induced platelet aggregability was enhanced in the last minute of exercise followed by a decreased aggregability 1 h after. Adrenaline-induced platelet aggregation showed the same attenuation after exercise but no change during work. The release products beta-thromboglobulin and serotonin in plasma showed significant increases after exercise. This is taken as evidence of an enhanced platelet activity following exercise. A normal stress-response, measured as increase in cyclic AMP in plasma, was observed. In conclusion, platelets are activated following moderate exercise and it seems valid to include the post-exercise period in future studies.

Adenosine Diphosphate↗

PubMed1996

Effects of ingested fluids on exercise capacity and on cardiovascular and metabolic responses to prolonged exercise in man.

It is well established that the ingestion of carbohydrate-containing drinks can improve the performance of prolonged exercise. The present study examined the effects of ingestion of water and two dilute glucose-electrolyte drinks on exercise performance and on cardiovascular and metabolic responses to exercise. Twelve subjects exercised to exhaustion on a cycle ergometer at a workload corresponding to 70% of maximum oxygen uptake (VO2,max) on five occasions each separated by 1 week. The first trial served to accustom subjects to experimental conditions. On one trial, no drinks were given and on the others subjects drank 100 ml every 10 min. Drinks consisted of water, an isotonic glucose-electrolyte solution (I: 200 mmol/l glucose; 35 mmol/l NA2; 310 mosmol/kg) and a hypotonic glucose-electrolyte solution (H: 90 mmol/l glucose; 60 mmol/l Na+; 240 mosmol/kg). Treatment order was randomized. Blood and expired air samples were taken and heart rate and rectal temperature measured at intervals during exercise. Median exercise time was greatest for treatment H (110.3 min) followed by treatment I (107.3 min), water (93.1) and no drink (80.7). Endurance times differed significantly overall, and for pairwise comparisons (P < 0.01) between the no-drink trial and both treatments H and I: a difference between water and no drink was seen at the 5% level. At exhaustion, a significant treatment difference was found for the change in plasma volume, with the greatest decrease (6.7%) on the no-drink trial and the smallest decrease (0.5%) on treatment H. Significant treatment effects were also observed for heart rate, rectal temperature and serum osmolality. The results suggest that the ingestion of glucose-electrolyte drinks can improve exercise performance even when the amount of added glucose is small, and that performance may also be enhanced, albeit to a lesser degree, by ingestion of water.

Adult↗

PubMed1987

Effect of exercise intensity and starvation on activation of branched-chain keto acid dehydrogenase by exercise.

Branched-chain keto acid (BCKA) dehydrogenase activity was examined in rat skeletal muscle as a function of exercise intensity and nutritional status. The activity of BCKA dehydrogenase increased with increasing exercise intensity, showing increases over resting values of 76, 172, and 245% at 10, 20, and 30 m X min-1. The exercise-induced increase in BCKA dehydrogenase activity was the same in the gastrocnemius and in the quadriceps muscles. Rapid removal of the muscle after death is essential because the activity of BCKA dehydrogenase decreased rapidly after death. Thus the likely reasons Wagenmakers et al. (Biochem. J. 223: 815-821, 1984) found exercise caused a much smaller increase in BCKA dehydrogenase activity than Kasperek et al. [Am. J. Physiol. 248 (Regulatory Integrative Comp. Physiol. 17): R166-R171, 1985] are differences in muscle removal time and the duration of exercise. Starvation for 24 h before exercise increased the exercise-induced activation of BCKA dehydrogenase by 160%, which suggests that the increased BCKA dehydrogenase activity is in response to an increased requirement for citric acid cycle intermediates.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed2001

Exercise-induced oxidative stress affects erythrocytes in sedentary rats but not exercise-trained rats.

Oxidant stress is one of the factors proposed to be responsible for damaged erythrocytes observed during and after exercise. The impact of exertional oxidant stress after acute exhaustive treadmill running on erythrocyte damage was investigated in sedentary (Sed) and exercise-trained (ET) rats treated with or without antioxidant vitamins C and E. Exhaustive exercise led to statistically significant increments in the levels of thiobarbituric acid-reactive substance (TBARS) and H2O2-induced TBARS in Sed rats and resulted in functional and structural alterations in erythrocytes (plasma hemoglobin concentrations, methemoglobin levels, and rise in osmotic fragility of erythrocytes with decrease in erythrocyte deformability). Administration of antioxidant vitamin for 1 mo before exhaustive exercises prevented lipid peroxidation (TBARS, H2O2-induced TBARS) in Sed rats without any functional or structural alterations in erythrocytes. Parameters indicating erythrocyte lipid peroxidation and deterioration after exhaustive exercise in rats trained regularly with treadmill running for 1 mo were not different from those in Sed controls. Erythrocyte lipid peroxidation (TBARS) increased in exhausted-ET rats compared with ET controls; however, the plasma hemoglobin, methemoglobin levels, and erythrocyte osmotic fragility and deformability did not differ. Exhaustive exercise-induced lipid peroxidation in ET rats on antioxidant vitamin treatment was prevented, whereas functional and structural parameters of erythrocytes were not different from those of the ET controls. We conclude that exertional oxidant stress contributed to erythrocyte deterioration due to exercise in Sed but not in ET rats.

Animals↗

PubMed2003

An analysis of undergraduate exercise science programs: an exercise science curriculum survey.

Undergraduate exercise science programs develop curricula by referring to standards set by professional organizations. A web-based survey was administered to 235 institutions with exercise science undergraduate programs to evaluate their adherence to stated curricular guidelines. Results indicate that 29% of institutions considered American College of Sports Medicine (ACSM) Knowledge, skills, and abilities (KSAs); 33% both ACSM and National Association for Sport and Physical Education (NASPE) guidelines; 6% ACSM, NASPE, and National Strength and Conditioning Association (NSCA); 8% ACSM, NASPE, NSCA, and American Society of Exercise Physiologists, and 5% NASPE. The two largest subgroups had good compliance with the areas of exercise physiology, biomechanics, and human anatomy and physiology. However, neither subgroup adhered to the areas of exercise prescription, testing, and implementation; exercise and aging; or exercise with special populations. Regardless of the implemented guideline(s), most institutions placed minimal emphasis on areas related to health promotion and many curricula did not require any field experience.

Accreditation↗

PubMed1975

Metabolic effects of exercise. I. Effect of exercise on serum lipids and lipogenesis in rats.

To evaluate the metabolic effects of exercise, three groups of exercised male rats were compared to their sedentary controls at the end of 10 wk of voluntary exercise in rodent activity cages. Exercises rats consumed more food than sedentary rats but had greater weight gain only at the higher levels of activity. Exercised rats had significanlty lower serum triglycerides and higher values of adipose tissue alpha-glycerophosphate dehydrogenase activity. At higher levels of physical activity, the exercised rats enhibited larger adrenal glands and lower values of hepatic glucose-6-phosphate dehydrogenase. It is concluded that specific levels of voluntary exercise are needed to achieve specific metabolic effects.

Adipose Tissue↗

PubMed2000

Cardiovascular exercise and wellness. Exercise training for cardiac rehabilitation patients: meeting the challenges of the millennium.

Exercise training for cardiac rehabilitation has evolved over the past decades in response to a growing knowledge base in exercise physiology, an expanding understanding to the knowledge base of coronary disease, and a change in the patients presenting for cardiac rehabilitation. The patient population has changed from a post myocardial infarction patient group, to patients who have had coronary artery revascularization (coronary artery bypass surgery or percutaneous transluminal coronary angioplasty) with the implantation of intraarterial stents. Program goals have evolved from enhancing endurance fitness in deconditioned patients to initiating the long-term adoption of an active exercising lifestyle with the use of strength training to complement endurance training. An increased understanding of behavioral issues in the adoption of an active lifestyle will influence the evolution of cardiac rehabilitation exercise training. During the next several years, it is anticipated that the patient population will change to include patients with significant left ventricular systolic dysfunction and congestive heart failure. The exercise training programs will then further evolve to reflect the successful exercise training formats utilized in the multicenter trials of exercise training for patients with congestive heart failure. (c) 2000 by CHF, Inc.

Journal Article↗

PubMed1990

Exercise induces recruitment of the "insulin-responsive glucose transporter". Evidence for distinct intracellular insulin- and exercise-recruitable transporter pools in skeletal muscle.

Acute exercise, like insulin, increases D-glucose uptake into rat hind limb muscles. Here we examine the distribution of the muscle glucose transporters GLUT-4 and GLUT-1 in plasma membrane and intracellular membrane fractions of skeletal muscle prepared from control, exercised, and acutely insulin-treated rats. Immunoblotting with an anti-GLUT-4 polyclonal antibody showed that acute insulin treatment (by hind limb perfusion or in vivo injection) increased GLUT-4 transporters in a plasma membrane fraction and decreased them in an intracellular membrane fraction. Exercise also increased the GLUT-4 transporters in the plasma membrane, but in contrast to insulin, did not significantly decrease them in the intracellular fraction. Immunoblotting with anti-GLUT-1 antibody revealed that this transporter is largely localized in the plasma membrane. Neither insulin nor exercise significantly increased GLUT-1 transporters in the plasma membrane. The data show that GLUT-4 is an insulin-responsive glucose transporter in skeletal muscle and, furthermore, that GLUT-4 also responds to acute exercise. The results are consistent with recruitment of GLUT-4 glucose transporters to the plasma membrane from intracellular stores. Moreover, exercise-sensitive GLUT-4 transporters do not originate from the insulin-sensitive intracellular membrane fraction, suggesting the existence of distinct intracellular insulin- and exercise-recruitable GLUT-4 transporter pools.

Animals↗

PubMed1987

Effect of nicorandil on exercise performance in patients with effort angina: a multicenter trial using a treadmill exercise test.

The effects of a single oral dose (20 mg) of a new vasodilator, nicorandil, on exercise performance were assessed in 29 patients with stable effort angina using a symptom-limited treadmill exercise test. A single-blind, placebo-controlled, randomized, crossover design was employed. Compared with placebo, 20 mg of nicorandil significantly increased maximal exercise duration and time to 1 mm of ST-segment depression at 1, 3, and 6 h after administration. Systolic blood pressure was reduced both at rest and during exercise. Heart rate increase during exercise did not differ significantly compared with control, though resting heart rate was increased. The maximal pressure-rate product at peak exercise was increased in association with increased exercise time in about half of the patients, while it was unchanged or decreased in the others. It was suggested that nicorandil may act by either reducing myocardial oxygen demand and/or increasing myocardial oxygen supply.

Adult↗

PubMed1982

Post-exercise ketosis and the hormone response to exercise: a review.

Post-exercise ketosis was first described in 1909 by Forssner, who found that his daily excretion of acetone in the urine was increased on days when he had undertaken a brisk walk in the morning. Athletes on unrestricted diets eat more, particularly carbohydrates, than non-athletes, and have lower post-exercise ketone body levels. They also have lower plasma glucagon, growth hormone, catecholamine, and free-fatty acid levels during sub-maximal exercise. On a standard 12 MJ/d diet, however, non-athletes have the lower post-exercise ketone body levels. The hormone response of athletes and non-athletes to exercise can similarly be reversed by dietary manipulation. The carbohydrate status of the body is, therefore, probably the main determinant of the type of blood hormone profile that develops during exercise, and the degree of ketosis that develops after exercise.

Acidosis↗

PubMed1998

Changes in plasma atrial natriuretic peptide concentration in exercising horses in relation to hydration status and exercise intensity.

OBJECTIVE: To investigate effects of hydration status and exercise intensity on plasma atrial natriuretic peptide (ANP) concentration in exercising horses. ANIMALS: 4 trained Standardbreds. PROCEDURE: Horses performed a 40-minute exercise test at 65 to 70% maximal heart rate (HRmax; no incline) and a 12-minute test at approximately 90% HRmax (3.5 degrees incline). The 40-minute test was performed with ad libitum access to drinking water (normohydration), after water had been withheld for 24 hours (dehydration), and 30 minutes after 12 L of water at body temperature had been given via nasogastric tube (hyperhydration). The 12-minute test was only performed with normohydrated horses. RESULTS: Plasma ANP concentration was higher toward the end of exercise during hyperhydration than during the other 2 hydration states, and the area under the plasma ANP concentration curve was significantly greater during hyperhydration than during dehydration. The maximal plasma ANP value induced during the 12-minute test was similar to that of the 40-minute test. After the 12-minute test, plasma ANP concentration did not decrease during the first 30 minutes of recovery, whereas after the 40-minute test, plasma ANP concentration decreased by approximately 30% during the same period. CONCLUSIONS: Hydration status can affect plasma ANP concentration in horses during submaximal exercise. Maximal plasma ANP concentration was similar at the 2 exercise intensities studied, but the postexercise return to baseline values differed. CLINICAL RELEVANCE: Changes in hydration status can cause alterations in plasma concentration of ANP, one of the hormones involved in the control of cardiovascular functions during exercise.

Animals↗