The Effect of Fitness on Cardiac Work with and without Metoprolol

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dc.contributor.advisorPeter Raven
dc.contributor.committeeMemberMichael Smith
dc.contributor.committeeMemberRobert Mallet
dc.creatorHawkins, Megan Nicole
dc.date.accessioned2019-08-22T19:50:19Z
dc.date.available2019-08-22T19:50:19Z
dc.date.issued2008-07-01
dc.date.submitted2013-08-06T13:54:06-07:00
dc.description.abstractHawkins, Megan Nicole, The Effect of Fitness on Cardiac Work with and without Metoprolol. Doctor of Philosophy (Biomedical Science), July 2008; 128 pp; 3 tables; 17 figures; bibliography. Chronic endurance exercise adaptations of the cardiovascular and skeletal muscle systems. The mechanisms by which these adaptations occur, and their effect on the physiological response to exercise, have not been fully elucated. In addition, the classic concept of the role of maximal oxygen consumption (Vo2max) as a parametric index of cardiorespiratory capacity has been questioned. Therefore the purpose of the investigations presented within this dissertation was to: i)retrospectively analyze 156 incremental exercise stress tests and supramaximal exercise tests to verify that VO2 does indeed attain a maximal value; ii)evaluate the effects of cardioselective beta-adrenergic blockade on the ability to maintain cardiac work in average trained and endurance exercise trained subjects during moderate (45% VO2max) and heavy (70% Vo2max) intensity cycling exercise; and iii) determine the effect of aerobic fitness on resting and peak leg vascular conductance and the change in central blood volume observed during the onset of cycling exercise. In the first investigation we demonstrated that highly trained runners capable of maintaining supramaximal workloads achieved a VO2 that rarely exceeded the VO2max value obtained during an incremental exercise stress test. In the second investigation we demonstrated that acute β1-adrenergic receptor (βAR) inhibition reduced cardiac output, cardiac work and cardiac efficiency in endurance trained athletes during moderate and heavy intensity exercise. However, in average trained individuals these same variables were not affected during moderate exercise intensity, but were reduced at heavy intensity exercise. We concluded that βAR blockade impaired the more efficient Frank-Starling mechanism in endurance trained athletes but remained functional in average trained subjects during moderate exercise intensities. In the third investigation we demonstrated that endurance athletes responded to the onset of exercise with a larger increase in central blood volume than average trained individuals. In addition, resting and post-ischemic leg blood glow and leg vascular conductance were greater in the exercise training-induced adaptations of the skeletal muscle vasculature resulted in larger conductance capacity of the working muscle in response to increases in oxygen demand and enabled a greater increase in muscle blood flow from rest to exercise.
dc.format.mimetypeapplication/pdf
dc.identifier.urihttps://hdl.handle.net/20.500.12503/27080
dc.language.isoen
dc.provenance.legacyDownloads0
dc.subjectAnatomy
dc.subjectBiological Factors
dc.subjectBiomechanics
dc.subjectCardiovascular System
dc.subjectExercise Physiology
dc.subjectExercise Science
dc.subjectInvestigative Techniques
dc.subjectKinesiology
dc.subjectKinesiotherapy
dc.subjectLife Sciences
dc.subjectMedicine and Health Sciences
dc.subjectMusculoskeletal System
dc.subjectOther Kinesiology
dc.subjectRehabilitation and Therapy
dc.subjectSomatic Bodywork and Related Therapeutic Practices
dc.subjectSports Sciences
dc.subjectFitness
dc.subjectcardiac work
dc.subjectMetoprolol
dc.subjectcardiovascular system
dc.subjectskeletal muscle system
dc.subjectexercise
dc.subjectmaximal oxygen consumption
dc.subjectV02max
dc.subjectcycling exercise
dc.subjectathletes
dc.subjectcardiac efficiency
dc.subjectβAR blockade
dc.subjectFrank-Starling mechanism
dc.titleThe Effect of Fitness on Cardiac Work with and without Metoprolol
dc.typeDissertation
dc.type.materialtext
thesis.degree.departmentGraduate School of Biomedical Sciences
thesis.degree.disciplineBiomedical Sciences
thesis.degree.grantorUniversity of North Texas Health Science Center at Fort Worth
thesis.degree.nameDoctor of Philosophy

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