Exercise Induced Cardiac Dysfunction Following Prolonged Exercise in Ambient Environment in Road Cyclists

Abstract

Exercise induced cardiac dysfunction is generally associated with cardiovascular disease. However a transient reduction in systolic and diastolic performance after very prolonged exercise has been successfully demonstrated by many researchers. PURPOSE: The purpose of this study is to examine cardiac function following a 100 mile ride in a high ambient temperature environment by healthy, competitive cyclists. METHODS: Subjects were six (n=6) competitive cyclists racing in the Hotter-N- HellTM Hundred road race. Measures (pre/post) included the following: weight (kg); E:A ratio (ventricular compliance), stroke volume (ml) and ejection fraction (%) through echocardiography. Additional measures included age (y), training status (hrs*week−1), racing experience (y), time required to finish the race (hrs.), height (cm), average race heart rate (b*min.−1), urine specific gravity, and post race blood troponin I to assess possible myocardial cellular damage. Prior to testing, all subjects signed an informed consent approved by the university Humans as Subjects Review Committee. RESULTS: Subject means (SD) were the following: age, 24.2 (1.2) y; height, 181.1 (5.5) cm; training status, 18 (2.4) hrs.*week−1; racing experience, 5.8 (4.6) y; average race heart rate, 159.3 (3.9) b*min.−1; pre/post E:A ratio, 2.04 (.41)/ 1.27 (.39); pre/post stroke volume, 98.6 (21.6)/ 72.6 (11.8) ml*min.−1; troponin I, 0.13 (.15), Ejection fraction pre/post, 67.3(3.8)/65.1(2.2)%, time to finish the ride 4.05 (0.54) hrs. Significant (p< 0.05) differences were determined between pre/post measures for E:A ratio, stroke volume, and pre/post weight, 76.4 (5.9)/ 72.4 (1.8) kg. Troponin I was elevated above established level of 0.03 for cellular disruption. Urine specific gravity at 1.02 (.01) did not indicate significant dehydration. CONCLUSION: The aforementioned significant differences in E:A ratio (i.e., ventricular compliance) and stroke volume indicate reduced cardiac function indicative of cardiac fatigue following a 100 mile bicycle race in high ambient temperatures. In addition, the elevated blood troponin I levels are indicative of myocardial cellular damage following this effort, which may have facilitated diastolic dysfunction.