Exercise Tolerance: The exercise capacity of an individual as measured by endurance (maximal exercise duration and/or maximal attained work load) during an EXERCISE TEST.Exercise Test: Controlled physical activity which is performed in order to allow assessment of physiological functions, particularly cardiovascular and pulmonary, but also aerobic capacity. Maximal (most intense) exercise is usually required but submaximal exercise is also used.Exercise Therapy: A regimen or plan of physical activities designed and prescribed for specific therapeutic goals. Its purpose is to restore normal musculoskeletal function or to reduce pain caused by diseases or injuries.Exercise: Physical activity which is usually regular and done with the intention of improving or maintaining PHYSICAL FITNESS or HEALTH. Contrast with PHYSICAL EXERTION which is concerned largely with the physiologic and metabolic response to energy expenditure.Physical Exertion: Expenditure of energy during PHYSICAL ACTIVITY. Intensity of exertion may be measured by rate of OXYGEN CONSUMPTION; HEAT produced, or HEART RATE. Perceived exertion, a psychological measure of exertion, is included.Drug Tolerance: Progressive diminution of the susceptibility of a human or animal to the effects of a drug, resulting from its continued administration. It should be differentiated from DRUG RESISTANCE wherein an organism, disease, or tissue fails to respond to the intended effectiveness of a chemical or drug. It should also be differentiated from MAXIMUM TOLERATED DOSE and NO-OBSERVED-ADVERSE-EFFECT LEVEL.Oxygen Consumption: The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)Dyspnea: Difficult or labored breathing.Physical Endurance: The time span between the beginning of physical activity by an individual and the termination because of exhaustion.Immune Tolerance: The specific failure of a normally responsive individual to make an immune response to a known antigen. It results from previous contact with the antigen by an immunologically immature individual (fetus or neonate) or by an adult exposed to extreme high-dose or low-dose antigen, or by exposure to radiation, antimetabolites, antilymphocytic serum, etc.Breathing Exercises: Therapeutic exercises aimed to deepen inspiration or expiration or even to alter the rate and rhythm of respiration.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Pulmonary Disease, Chronic Obstructive: A disease of chronic diffuse irreversible airflow obstruction. Subcategories of COPD include CHRONIC BRONCHITIS and PULMONARY EMPHYSEMA.Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Lung Diseases, Obstructive: Any disorder marked by obstruction of conducting airways of the lung. AIRWAY OBSTRUCTION may be acute, chronic, intermittent, or persistent.Heart Failure: A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (VENTRICULAR DYSFUNCTION), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as MYOCARDIAL INFARCTION.Respiratory Function Tests: Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc.Pulmonary Gas Exchange: The exchange of OXYGEN and CARBON DIOXIDE between alveolar air and pulmonary capillary blood that occurs across the BLOOD-AIR BARRIER.Xamoterol: A phenoxypropanolamine derivative that is a selective beta-1-adrenergic agonist.Angina Pectoris: The symptom of paroxysmal pain consequent to MYOCARDIAL ISCHEMIA usually of distinctive character, location and radiation. It is thought to be provoked by a transient stressful situation during which the oxygen requirements of the MYOCARDIUM exceed that supplied by the CORONARY CIRCULATION.Glucose Tolerance Test: A test to determine the ability of an individual to maintain HOMEOSTASIS of BLOOD GLUCOSE. It includes measuring blood glucose levels in a fasting state, and at prescribed intervals before and after oral glucose intake (75 or 100 g) or intravenous infusion (0.5 g/kg).Double-Blind Method: A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment.Forced Expiratory Volume: Measure of the maximum amount of air that can be expelled in a given number of seconds during a FORCED VITAL CAPACITY determination . It is usually given as FEV followed by a subscript indicating the number of seconds over which the measurement is made, although it is sometimes given as a percentage of forced vital capacity.Anaerobic Threshold: The oxygen consumption level above which aerobic energy production is supplemented by anaerobic mechanisms during exercise, resulting in a sustained increase in lactate concentration and metabolic acidosis. The anaerobic threshold is affected by factors that modify oxygen delivery to the tissues; it is low in patients with heart disease. Methods of measurement include direct measure of lactate concentration, direct measurement of bicarbonate concentration, and gas exchange measurements.Respiratory Muscles: These include the muscles of the DIAPHRAGM and the INTERCOSTAL MUSCLES.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Cross-Over Studies: Studies comparing two or more treatments or interventions in which the subjects or patients, upon completion of the course of one treatment, are switched to another. In the case of two treatments, A and B, half the subjects are randomly allocated to receive these in the order A, B and half to receive them in the order B, A. A criticism of this design is that effects of the first treatment may carry over into the period when the second is given. (Last, A Dictionary of Epidemiology, 2d ed)Quality of Life: A generic concept reflecting concern with the modification and enhancement of life attributes, e.g., physical, political, moral and social environment; the overall condition of a human life.Counterpulsation: A technique for assisting the circulation by decreasing the afterload of the left ventricle and augmenting the diastolic pressure. It may be achieved by intra-aortic balloon, or by implanting a special pumping device in the chest, or externally by applying a negative pressure to the lower extremities during cardiac systole.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Hemodynamics: The movement and the forces involved in the movement of the blood through the CARDIOVASCULAR SYSTEM.Walking: An activity in which the body advances at a slow to moderate pace by moving the feet in a coordinated fashion. This includes recreational walking, walking for fitness, and competitive race-walking.Rest: Freedom from activity.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Respiration: The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= OXYGEN CONSUMPTION) or cell respiration (= CELL RESPIRATION).Cardiac Output: The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat).Chronic Disease: Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care. (Dictionary of Health Services Management, 2d ed)Inspiratory Capacity: The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration. It is the sum of the TIDAL VOLUME and the INSPIRATORY RESERVE VOLUME. Common abbreviation is IC.Heart Function Tests: Examinations used to diagnose and treat heart conditions.Muscle Strength: The amount of force generated by MUSCLE CONTRACTION. Muscle strength can be measured during isometric, isotonic, or isokinetic contraction, either manually or using a device such as a MUSCLE STRENGTH DYNAMOMETER.Stroke Volume: The amount of BLOOD pumped out of the HEART per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume.Transplantation Tolerance: An induced state of non-reactivity to grafted tissue from a donor organism that would ordinarily trigger a cell-mediated or humoral immune response.Vital Capacity: The volume of air that is exhaled by a maximal expiration following a maximal inspiration.Lactic Acid: A normal intermediate in the fermentation (oxidation, metabolism) of sugar. The concentrated form is used internally to prevent gastrointestinal fermentation. (From Stedman, 26th ed)Adaptation, Physiological: The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Spirometry: Measurement of volume of air inhaled or exhaled by the lung.Isosorbide Dinitrate: A vasodilator used in the treatment of ANGINA PECTORIS. Its actions are similar to NITROGLYCERIN but with a slower onset of action.Oxygen Inhalation Therapy: Inhalation of oxygen aimed at restoring toward normal any pathophysiologic alterations of gas exchange in the cardiopulmonary system, as by the use of a respirator, nasal catheter, tent, chamber, or mask. (From Dorland, 27th ed & Stedman, 25th ed)Neurocirculatory Asthenia: A clinical syndrome characterized by palpitation, SHORTNESS OF BREATH, labored breathing, subjective complaints of effort and discomfort, all following slight PHYSICAL EXERTION. Other symptoms may be DIZZINESS, tremulousness, SWEATING, and INSOMNIA. Neurocirculatory asthenia is most typically seen as a form of anxiety disorder.Electrocardiography: Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY.Muscle Fatigue: A state arrived at through prolonged and strong contraction of a muscle. Studies in athletes during prolonged submaximal exercise have shown that muscle fatigue increases in almost direct proportion to the rate of muscle glycogen depletion. Muscle fatigue in short-term maximal exercise is associated with oxygen lack and an increased level of blood and muscle lactic acid, and an accompanying increase in hydrogen-ion concentration in the exercised muscle.Ebstein Anomaly: A congenital heart defect characterized by downward or apical displacement of the TRICUSPID VALVE, usually with the septal and posterior leaflets being attached to the wall of the RIGHT VENTRICLE. It is characterized by a huge RIGHT ATRIUM and a small and less effective right ventricle.Propanolamines: AMINO ALCOHOLS containing the propanolamine (NH2CH2CHOHCH2) group and its derivatives.Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.Pulmonary Ventilation: The total volume of gas inspired or expired per unit of time, usually measured in liters per minute.Metoprolol: A selective adrenergic beta-1 blocking agent that is commonly used to treat ANGINA PECTORIS; HYPERTENSION; and CARDIAC ARRHYTHMIAS.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Bronchitis: Inflammation of the large airways in the lung including any part of the BRONCHI, from the PRIMARY BRONCHI to the TERTIARY BRONCHI.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Bicycling: The use of a bicycle for transportation or recreation. It does not include the use of a bicycle in studying the body's response to physical exertion (BICYCLE ERGOMETRY TEST see EXERCISE TEST).Glycogen Storage Disease Type V: Glycogenosis due to muscle phosphorylase deficiency. Characterized by painful cramps following sustained exercise.Adrenergic beta-Antagonists: Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety.Ventricular Function, Left: The hemodynamic and electrophysiological action of the left HEART VENTRICLE. Its measurement is an important aspect of the clinical evaluation of patients with heart disease to determine the effects of the disease on cardiac performance.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.Physical Fitness: The ability to carry out daily tasks and perform physical activities in a highly functional state, often as a result of physical conditioning.Single-Blind Method: A method in which either the observer(s) or the subject(s) is kept ignorant of the group to which the subjects are assigned.Ventricular Dysfunction, Left: A condition in which the LEFT VENTRICLE of the heart was functionally impaired. This condition usually leads to HEART FAILURE; MYOCARDIAL INFARCTION; and other cardiovascular complications. Diagnosis is made by measuring the diminished ejection fraction and a depressed level of motility of the left ventricular wall.Cardiac Output, Low: A state of subnormal or depressed cardiac output at rest or during stress. It is a characteristic of CARDIOVASCULAR DISEASES, including congenital, valvular, rheumatic, hypertensive, coronary, and cardiomyopathic. The serious form of low cardiac output is characterized by marked reduction in STROKE VOLUME, and systemic vasoconstriction resulting in cold, pale, and sometimes cyanotic extremities.Diastole: Post-systolic relaxation of the HEART, especially the HEART VENTRICLES.Physical Conditioning, Animal: Diet modification and physical exercise to improve the ability of animals to perform physical activities.Bronchodilator Agents: Agents that cause an increase in the expansion of a bronchus or bronchial tubes.Energy Metabolism: The chemical reactions involved in the production and utilization of various forms of energy in cells.Blood Glucose: Glucose in blood.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Nitroglycerin: A volatile vasodilator which relieves ANGINA PECTORIS by stimulating GUANYLATE CYCLASE and lowering cytosolic calcium. It is also sometimes used for TOCOLYSIS and explosives.Resistance Training: A type of strength-building exercise program that requires the body muscle to exert a force against some form of resistance, such as weight, stretch bands, water, or immovable objects. Resistance exercise is a combination of static and dynamic contractions involving shortening and lengthening of skeletal muscles.Hypertension, Pulmonary: Increased VASCULAR RESISTANCE in the PULMONARY CIRCULATION, usually secondary to HEART DISEASES or LUNG DISEASES.Fatigue: The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.Ipratropium: A muscarinic antagonist structurally related to ATROPINE but often considered safer and more effective for inhalation use. It is used for various bronchial disorders, in rhinitis, and as an antiarrhythmic.Heart: The hollow, muscular organ that maintains the circulation of the blood.Running: An activity in which the body is propelled by moving the legs rapidly. Running is performed at a moderate to rapid pace and should be differentiated from JOGGING, which is performed at a much slower pace.Bisoprolol: A cardioselective beta-1 adrenergic blocker. It is effective in the management of HYPERTENSION and ANGINA PECTORIS.Administration, Oral: The giving of drugs, chemicals, or other substances by mouth.Coronary Disease: An imbalance between myocardial functional requirements and the capacity of the CORONARY VESSELS to supply sufficient blood flow. It is a form of MYOCARDIAL ISCHEMIA (insufficient blood supply to the heart muscle) caused by a decreased capacity of the coronary vessels.Muscle Stretching Exercises: Exercises that stretch the muscle fibers with the aim to increase muscle-tendon FLEXIBILITY, improve RANGE OF MOTION or musculoskeletal function, and prevent injuries. There are various types of stretching techniques including active, passive (relaxed), static, dynamic (gentle), ballistic (forced), isometric, and others.Nafronyl: A drug used in the management of peripheral and cerebral vascular disorders. It is claimed to enhance cellular oxidative capacity and to be a spasmolytic. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1310) It may also be an antagonist at 5HT-2 serotonin receptors.Echocardiography, Doppler: Measurement of intracardiac blood flow using an M-mode and/or two-dimensional (2-D) echocardiogram while simultaneously recording the spectrum of the audible Doppler signal (e.g., velocity, direction, amplitude, intensity, timing) reflected from the moving column of red blood cells.Respiratory Mechanics: The physical or mechanical action of the LUNGS; DIAPHRAGM; RIBS; and CHEST WALL during respiration. It includes airflow, lung volume, neural and reflex controls, mechanoreceptors, breathing patterns, etc.Vasodilator Agents: Drugs used to cause dilation of the blood vessels.Self Tolerance: The normal lack of the ability to produce an immunological response to autologous (self) antigens. A breakdown of self tolerance leads to autoimmune diseases. The ability to recognize the difference between self and non-self is the prime function of the immune system.Arm: The superior part of the upper extremity between the SHOULDER and the ELBOW.Clinical Trials as Topic: Works about pre-planned studies of the safety, efficacy, or optimum dosage schedule (if appropriate) of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects. This concept includes clinical trials conducted both in the U.S. and in other countries.Lung Volume Measurements: Measurement of the amount of air that the lungs may contain at various points in the respiratory cycle.Cardiovascular Agents: Agents that affect the rate or intensity of cardiac contraction, blood vessel diameter, or blood volume.Cardiac Volume: The volume of the HEART, usually relating to the volume of BLOOD contained within it at various periods of the cardiac cycle. The amount of blood ejected from a ventricle at each beat is STROKE VOLUME.Pulmonary Emphysema: Enlargement of air spaces distal to the TERMINAL BRONCHIOLES where gas-exchange normally takes place. This is usually due to destruction of the alveolar wall. Pulmonary emphysema can be classified by the location and distribution of the lesions.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Recovery of Function: A partial or complete return to the normal or proper physiologic activity of an organ or part following disease or trauma.Propranolol: A widely used non-cardioselective beta-adrenergic antagonist. Propranolol has been used for MYOCARDIAL INFARCTION; ARRHYTHMIA; ANGINA PECTORIS; HYPERTENSION; HYPERTHYROIDISM; MIGRAINE; PHEOCHROMOCYTOMA; and ANXIETY but adverse effects instigate replacement by newer drugs.Cardiac Pacing, Artificial: Regulation of the rate of contraction of the heart muscles by an artificial pacemaker.Hand Strength: Force exerted when gripping or grasping.Questionnaires: Predetermined sets of questions used to collect data - clinical data, social status, occupational group, etc. The term is often applied to a self-completed survey instrument.Glucose Intolerance: A pathological state in which BLOOD GLUCOSE level is less than approximately 140 mg/100 ml of PLASMA at fasting, and above approximately 200 mg/100 ml plasma at 30-, 60-, or 90-minute during a GLUCOSE TOLERANCE TEST. This condition is seen frequently in DIABETES MELLITUS, but also occurs with other diseases and MALNUTRITION.Cardiomyopathy, Dilated: A form of CARDIAC MUSCLE disease that is characterized by ventricular dilation, VENTRICULAR DYSFUNCTION, and HEART FAILURE. Risk factors include SMOKING; ALCOHOL DRINKING; HYPERTENSION; INFECTION; PREGNANCY; and mutations in the LMNA gene encoding LAMIN TYPE A, a NUCLEAR LAMINA protein.Random Allocation: A process involving chance used in therapeutic trials or other research endeavor for allocating experimental subjects, human or animal, between treatment and control groups, or among treatment groups. It may also apply to experiments on inanimate objects.Heart Ventricles: The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.Heart Diseases: Pathological conditions involving the HEART including its structural and functional abnormalities.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Electrocardiography, Ambulatory: Method in which prolonged electrocardiographic recordings are made on a portable tape recorder (Holter-type system) or solid-state device ("real-time" system), while the patient undergoes normal daily activities. It is useful in the diagnosis and management of intermittent cardiac arrhythmias and transient myocardial ischemia.Physical Education and Training: Instructional programs in the care and development of the body, often in schools. The concept does not include prescribed exercises, which is EXERCISE THERAPY.GlycogenElectric Stimulation Therapy: Application of electric current in treatment without the generation of perceptible heat. It includes electric stimulation of nerves or muscles, passage of current into the body, or use of interrupted current of low intensity to raise the threshold of the skin to pain.Regression Analysis: Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.Ethanolamines: AMINO ALCOHOLS containing the ETHANOLAMINE; (-NH2CH2CHOH) group and its derivatives.Salt-Tolerance: The ability of organisms to sense and adapt to high concentrations of salt in their growth environment.Asthma, Exercise-Induced: Asthma attacks following a period of exercise. Usually the induced attack is short-lived and regresses spontaneously. The magnitude of postexertional airway obstruction is strongly influenced by the environment in which exercise is performed (i.e. inhalation of cold air during physical exertion markedly augments the severity of the airway obstruction; conversely, warm humid air blunts or abolishes it).Carbazoles: Benzo-indoles similar to CARBOLINES which are pyrido-indoles. In plants, carbazoles are derived from indole and form some of the INDOLE ALKALOIDS.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Pacemaker, Artificial: A device designed to stimulate, by electric impulses, contraction of the heart muscles. It may be temporary (external) or permanent (internal or internal-external).Adrenergic beta-Agonists: Drugs that selectively bind to and activate beta-adrenergic receptors.Pilot Projects: Small-scale tests of methods and procedures to be used on a larger scale if the pilot study demonstrates that these methods and procedures can work.Pneumonectomy: The excision of lung tissue including partial or total lung lobectomy.Statistics, Nonparametric: A class of statistical methods applicable to a large set of probability distributions used to test for correlation, location, independence, etc. In most nonparametric statistical tests, the original scores or observations are replaced by another variable containing less information. An important class of nonparametric tests employs the ordinal properties of the data. Another class of tests uses information about whether an observation is above or below some fixed value such as the median, and a third class is based on the frequency of the occurrence of runs in the data. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1284; Corsini, Concise Encyclopedia of Psychology, 1987, p764-5)Exercise Movement Techniques: Methods or programs of physical activities which can be used to promote, maintain, or restore the physical and physiological well-being of an individual.Dietary Supplements: Products in capsule, tablet or liquid form that provide dietary ingredients, and that are intended to be taken by mouth to increase the intake of nutrients. Dietary supplements can include macronutrients, such as proteins, carbohydrates, and fats; and/or MICRONUTRIENTS, such as VITAMINS; MINERALS; and PHYTOCHEMICALS.Myocardial Infarction: NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Drug Administration Schedule: Time schedule for administration of a drug in order to achieve optimum effectiveness and convenience.Activities of Daily Living: The performance of the basic activities of self care, such as dressing, ambulation, or eating.Enalapril: An angiotensin-converting enzyme inhibitor that is used to treat HYPERTENSION and HEART FAILURE.Tomography, Emission-Computed, Single-Photon: A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.Weight Lifting: A sport in which weights are lifted competitively or as an exercise.Acclimatization: Adaptation to a new environment or to a change in the old.Antihypertensive Agents: Drugs used in the treatment of acute or chronic vascular HYPERTENSION regardless of pharmacological mechanism. Among the antihypertensive agents are DIURETICS; (especially DIURETICS, THIAZIDE); ADRENERGIC BETA-ANTAGONISTS; ADRENERGIC ALPHA-ANTAGONISTS; ANGIOTENSIN-CONVERTING ENZYME INHIBITORS; CALCIUM CHANNEL BLOCKERS; GANGLIONIC BLOCKERS; and VASODILATOR AGENTS.Stress, Physiological: The unfavorable effect of environmental factors (stressors) on the physiological functions of an organism. Prolonged unresolved physiological stress can affect HOMEOSTASIS of the organism, and may lead to damaging or pathological conditions.Angiotensin-Converting Enzyme Inhibitors: A class of drugs whose main indications are the treatment of hypertension and heart failure. They exert their hemodynamic effect mainly by inhibiting the renin-angiotensin system. They also modulate sympathetic nervous system activity and increase prostaglandin synthesis. They cause mainly vasodilation and mild natriuresis without affecting heart rate and contractility.Prognosis: A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations.Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Motor Activity: The physical activity of a human or an animal as a behavioral phenomenon.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Myocardial Ischemia: A disorder of cardiac function caused by insufficient blood flow to the muscle tissue of the heart. The decreased blood flow may be due to narrowing of the coronary arteries (CORONARY ARTERY DISEASE), to obstruction by a thrombus (CORONARY THROMBOSIS), or less commonly, to diffuse narrowing of arterioles and other small vessels within the heart. Severe interruption of the blood supply to the myocardial tissue may result in necrosis of cardiac muscle (MYOCARDIAL INFARCTION).Coronary Circulation: The circulation of blood through the CORONARY VESSELS of the HEART.Linear Models: Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Placebos: Any dummy medication or treatment. Although placebos originally were medicinal preparations having no specific pharmacological activity against a targeted condition, the concept has been extended to include treatments or procedures, especially those administered to control groups in clinical trials in order to provide baseline measurements for the experimental protocol.Drug Therapy, Combination: Therapy with two or more separate preparations given for a combined effect.Mice, Inbred C57BLCardiac Catheterization: Procedures in which placement of CARDIAC CATHETERS is performed for therapeutic or diagnostic procedures.Droughts: Prolonged dry periods in natural climate cycle. They are slow-onset phenomena caused by rainfall deficit combined with other predisposing factors.Ventricular Remodeling: The geometric and structural changes that the HEART VENTRICLES undergo, usually following MYOCARDIAL INFARCTION. It comprises expansion of the infarct and dilatation of the healthy ventricle segments. While most prevalent in the left ventricle, it can also occur in the right ventricle.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Insulin Resistance: Diminished effectiveness of INSULIN in lowering blood sugar levels: requiring the use of 200 units or more of insulin per day to prevent HYPERGLYCEMIA or KETOSIS.Sports: Activities or games, usually involving physical effort or skill. Reasons for engagement in sports include pleasure, competition, and/or financial reward.Cardiovascular Physiological Phenomena: Processes and properties of the CARDIOVASCULAR SYSTEM as a whole or of any of its parts.Administration, Inhalation: The administration of drugs by the respiratory route. It includes insufflation into the respiratory tract.Natriuretic Peptide, Brain: A PEPTIDE that is secreted by the BRAIN and the HEART ATRIA, stored mainly in cardiac ventricular MYOCARDIUM. It can cause NATRIURESIS; DIURESIS; VASODILATION; and inhibits secretion of RENIN and ALDOSTERONE. It improves heart function. It contains 32 AMINO ACIDS.Ergometry: Any method of measuring the amount of work done by an organism, usually during PHYSICAL EXERTION. Ergometry also includes measures of power. Some instruments used in these determinations include the hand crank and the bicycle ergometer.Lung Diseases: Pathological processes involving any part of the LUNG.Glucose: A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.Obesity: A status with BODY WEIGHT that is grossly above the acceptable or desirable weight, usually due to accumulation of excess FATS in the body. The standards may vary with age, sex, genetic or cultural background. In the BODY MASS INDEX, a BMI greater than 30.0 kg/m2 is considered obese, and a BMI greater than 40.0 kg/m2 is considered morbidly obese (MORBID OBESITY).Cardiotonic Agents: Agents that have a strengthening effect on the heart or that can increase cardiac output. They may be CARDIAC GLYCOSIDES; SYMPATHOMIMETICS; or other drugs. They are used after MYOCARDIAL INFARCT; CARDIAC SURGICAL PROCEDURES; in SHOCK; or in congestive heart failure (HEART FAILURE).Quadriceps Muscle: The quadriceps femoris. A collective name of the four-headed skeletal muscle of the thigh, comprised of the rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis.Peripheral Tolerance: The mechanism, in peripheral lymphoid organs (LYMPH NODES; SPLEEN; TONSILS; and mucosal-associated lymphoid tissue), that prevents mature lymphocytes from reacting to SELF-ANTIGENS. This is accomplished through a variety of means including CLONAL ANERGY and CLONAL DELETION.Lactates: Salts or esters of LACTIC ACID containing the general formula CH3CHOHCOOR.Cross-Sectional Studies: Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time.Myocardium: The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.Diabetes Mellitus, Type 2: A subclass of DIABETES MELLITUS that is not INSULIN-responsive or dependent (NIDDM). It is characterized initially by INSULIN RESISTANCE and HYPERINSULINEMIA; and eventually by GLUCOSE INTOLERANCE; HYPERGLYCEMIA; and overt diabetes. Type II diabetes mellitus is no longer considered a disease exclusively found in adults. Patients seldom develop KETOSIS but often exhibit OBESITY.Morphine: The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle.Body Composition: The relative amounts of various components in the body, such as percentage of body fat.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Swimming: An activity in which the body is propelled through water by specific movement of the arms and/or the legs. Swimming as propulsion through water by the movement of limbs, tail, or fins of animals is often studied as a form of PHYSICAL EXERTION or endurance.Coronary Angiography: Radiography of the vascular system of the heart muscle after injection of a contrast medium.Sweating: The process of exocrine secretion of the SWEAT GLANDS, including the aqueous sweat from the ECCRINE GLANDS and the complex viscous fluids of the APOCRINE GLANDS.Fatty Acids, Nonesterified: FATTY ACIDS found in the plasma that are complexed with SERUM ALBUMIN for transport. These fatty acids are not in glycerol ester form.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Cold Temperature: An absence of warmth or heat or a temperature notably below an accustomed norm.Forearm: Part of the arm in humans and primates extending from the ELBOW to the WRIST.Coronary Artery Bypass: Surgical therapy of ischemic coronary artery disease achieved by grafting a section of saphenous vein, internal mammary artery, or other substitute between the aorta and the obstructed coronary artery distal to the obstructive lesion.Skin Transplantation: The grafting of skin in humans or animals from one site to another to replace a lost portion of the body surface skin.Dehydration: The condition that results from excessive loss of water from a living organism.Cohort Studies: Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesized to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics.Dietary Carbohydrates: Carbohydrates present in food comprising digestible sugars and starches and indigestible cellulose and other dietary fibers. The former are the major source of energy. The sugars are in beet and cane sugar, fruits, honey, sweet corn, corn syrup, milk and milk products, etc.; the starches are in cereal grains, legumes (FABACEAE), tubers, etc. (From Claudio & Lagua, Nutrition and Diet Therapy Dictionary, 3d ed, p32, p277)Body Temperature: The measure of the level of heat of a human or animal.Pulmonary Artery: The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs.Pain Measurement: Scales, questionnaires, tests, and other methods used to assess pain severity and duration in patients or experimental animals to aid in diagnosis, therapy, and physiological studies.Risk Assessment: The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. (Last, Dictionary of Epidemiology, 1988)