Lally, DavidCaroll, Patricia A.2009-03-062009-03-062003-05http://hdl.handle.net/10125/6969vii, 65 leavesUltraendurance sports, allowing athletes eager to test the limits of their endurance, are becoming increasingly popular in the United States and throughout the world. The numbers of 100 mile running events; Ironman-distance triathlons (2.4 mile swim, 112 mile bike ride, 26.2 mile run); and multi day, multi-sports events such as the Eco Challenge are increasing. To date, few researchers have investigated the effects these ultraendurance events have on the human heart. In the early 1990's William Rowe suggested that permanent cardiac injury could develop in some endurance athletes in the absence of coronary atherosclerosis. Injury to the coronary endothelium as a result of endurance exercise could occur in athletes participating in multiple events if sufficient time is not allowed for endothelial repair. Rowe proposed that high levels of circulating catecholamines produced by endurance exercise might cause acute myocardial ischemia, patchy fibrosis, as well as coronary vasospasm (sudden, transient constriction of blood vessels). The vasospasm then produced high-sheer endothelial turbulence thus injuring the endothelium. These injuries suffered overtime would adversely affect the heart (Rowe 1992; 1993). In a review of catecholamine cardiotoxicity, Rona stated that the release of catecholamines during exercise might deplete the energy reserves of cardiac muscle cells and this depletion could ultimately result in necrosis. Moreover high-circulating levels of catecholamines might increase cardiac-muscle cell-membrane permeability (Rona 1985) Do events that test the upper limits of human endurance in fact have any adverse effects on the heart? If so, what are they? Are these effects transient or permanent? What is the minimum level of effort at which injury is first observed? These questions prompted this study and the results will contribute to the limited but increasing knowledge regarding the cardiac effects and/or side effects of ultraendurance exercise.All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.Thesis