CONCLUSION: Compared to ET, the similar cardiac output with lower LV wall stress and a greater LV relaxation with similar filling dynamics in sprint athletes indicates a specific ‘athlete’s heart’ that is characterized by different associations between demand, haemodynamics and LV mechanical function. Future investigations in patient populations are warranted. 2229 Board #2 May 31 9:30 AM - 11:30 AM Exercise-Induced Cardiac Fatigue is Similar Across Increasing Trail-Running Race Distances Alexandra M. Coates1, Katharine D. Currie2, Trevor J. King1, Philip J. Millar1, Jamie F. Burr1. 1University of Guelph, Guelph, ON, Canada. 2Michigan State University, East Lansing, MI. (Sponsor: Jamie Burr, FACSM) (No relationships reported) A transient reduction in cardiac function following prolonged endurance exercise, termed exercise-induced cardiac fatigue, has previously been reported following events ranging from 2-40hrs. Right-ventricular dysfunction has been demonstrated to occur prior to left-ventricular dysfunction and, similarly, diastolic impairments may occur prior to systolic impairments. While highlytrained athletes are more fatigue-resistant than lesser-trained subjects, the timing and magnitude of cardiac alterations following prolonged racing is unclear. PURPOSE: The aim of this study was to investigate the effects of varying distance trail running races on cardiac function in recreational runners of varying fitness levels, to determine the dose-response of cardiac fatigue. METHODS: Forty-three distance runners competing in the Sulphur Springs trail races (25k,n=9; 50k,n=13; 80k,n=13; 160k,n=8) completed pre and post testing measures including resting echocardiography, and an incremental running test to determine maximal oxygen consumption (VO2max). RESULTS: Mean race durations were as follows; 25k:2.5±0.3hrs, 50k: 6.0±2.0hrs, 80k: 11.6±1.8, and 160k: 25.2±3.6hrs (all P<0.001). Echocardiographic results indicated diastolic impairments of both ventricles, with minimal systolic impairments, across all race distances post-race. Of the parameters investigated, only early-to-late diastolic filling ratio (E/A) was different between groups such that the 160k racers did not have as great of a reduction (mean Δ-0.51±0.50, 160k Δ-0.20±0.45, P=0.02). All racers had decreased blood pressure (MAP pre: 94±10 vs post: 83±9mmHg, P<0.0001), and elevated heart rates (pre:55±8 vs post:78±12b/min, P<0.0001) post-race. Fitness (VO2max) and age were not related to changes in cardiac function, whereas race duration was related to changes in E/A ratio (r=0.37, P=0.02) only. Changes in diastolic blood pressure were related to many changes in cardiac function including peak longitudinal strain (r=0.34, P=0.03). CONCLUSIONS: Prolonged trail-races appear to alter diastolic function regardless of race duration, and fitness, likely due to similar reductions in blood pressure post-race. A clear relationship between race duration and level of cardiac impairment is not apparent. 2230 Board #3 May 31 9:30 AM - 11:30 AM Cardiovascular Adaptations During the Hormonal Transition of a Male-to-Female Transgender Athlete Shannon L. Wilson1, Andrew C. D'Lugos1, Nathan Serrano1, Theresa M. Jorgensen1, Joanna Harper2, Glenn A. Gaesser, FACSM1, Jared M. Dickinson, FACSM1, Siddhartha S. Angadi, FACSM1. 1Arizona State University, Phoenix, AZ. 2Providence Portland Medical Center, Portland, OR. (No relationships reported) PURPOSE: Cardiovascular consequences of female sex hormone exposure on human male biology are currently unknown. This level of investigation is critical given potential adverse outcomes reported in rodent models. This case study aimed to comprehensively assess cardiovascular phenotypes before and during estrogen treatment for gender reassignment METHODS:This is the case of a biologically male, distance runner (28 yr) undergoing male-to-female gender reassignment. Two baseline assessments were made prior to initiation of hormone treatment. Testing following initiation of estrogen treatment took place at 4-8 week intervals depending on subject’s availability. Testing included resting echocardiography for assessment of biventricular function, dual energy x-ray absorptiometry (DXA), and central vascular blood pressures and stiffness assessments. Treadmill-based VO2 peak and running economy, as well as non-invasive cardiac output and a-vO2 difference at rest and at peak exercise were quantified at each visit RESULTS: Throughout the first 12 months of treatment, stroke volume decreased (136 to 80 ml/beat) with an initial reduction in peak heart rate (ranged 188-180 bpm). Consequently, peak cardiac output declined (28.4 L/min to 15.5 L/min) while a-vO2 difference increased (11.6 to 19.9 ml O2/100 ml blood). This resulted in only a minor decrease in absolute VO 2 peak (3.3 to 3.1 L/min). Ejection fraction (calculated using modified Simpson’s method via echocardiogram) decreased (61% to 57%) along with left ventricular diastology (mitral valve E/e 6.0 to 4.1). Right Ventricular Fractional Area change was unaffected (53% to 53%), while measures of right heart diastology increased (tricuspid valve E/e 3.9 to 4.6). Both right ventricular (RV) and left ventricular (LV) strain initially improved with the addition of estrogen, before worsening over the course of hormone treatment (RV strain ranged from -36 to -31.5%; LV strain ranged from 23.5 to -19%) CONCLUSIONS: Therapeutic estrogen administration and testosterone blockade may adversely affect cardiopulmonary fitness via reduction in myocardial performance at peak exercise. This may be associated with a worsening of LV and RV strain at rest. More research is needed to examine the long-term effects of gender reassignment therapy on cardiovascular function 2231 Board #4 May 31 9:30 AM - 11:30 AM Cardiovascular Disease Risk In Middle-Aged Ultra-Endurance Athletes Nate P. Bachman1, Janée D. Terwoord1, Jennifer C. Richards1, Barry Braun, FACSM1, C Patrick Green2, Gary J. Luckasen2, Frank A. Dinenno1. 1Colorado State University, Fort Collins, CO. 2Medical Center of the Rockies Foundation, Loveland, CO. Email: nbachman@colostate.edu (No relationships reported) It is widely accepted that aerobic exercise reduces cardiovascular disease (CVD) risk. However, recent studies suggest that volumes of exercise that greatly exceed physical activity guidelines may be damaging to the heart. Currently, it is unclear if individuals who train for ultra-endurance races have an elevated risk of developing CVD compared to those that perform lower amounts of physical activity. Additionally, little work has been done to examine vascular function in these athletes. PURPOSE: To evaluate cardiovascular function and calculate CVD risk to determine if individuals that train for ultra-endurance races have a greater risk compared to individuals that engage in moderate physical activity. METHODS: We examined cardiovascular function in athletes (ATH, 14M/11F, 50±1 y) that had been training for ultra-endurance events for 10+ years and controls (CON, 9M/9F, 49±2 y) that were meeting current ACSM physical activity guidelines. We used cardiac computed tomography (CT) to calculate coronary artery calcium scores (CACS) and contrast-enhanced magnetic resonance imaging (MRI) to identify myocardial fibrosis (MF). Carotid-femoral pulse wave velocity (cfPWV) was used to evaluate aortic stiffness and ultrasound assessment of carotid intimamedia thickness (CIMT) was used to determine vascular structure of the carotid artery. Additionally, we used Doppler ultrasound to assess vascular endothelial function by measuring flowmediated dilation (FMD) of the brachial artery. Finally, we used a risk score calculator to determine 10-year CVD risk. RESULTS: CACS > 0 was observed in 8 ATH and 2 CON; however, the presence of CAC was not significantly different between groups (P>0.05). Additionally, no participant in ATH or CON had MF. ATH had lower cfPWV compared to CON (6.2±0.2 vs 6.9±0.2 m/s, P<0.05), while no difference in CIMT (ATH; 0.64±0.02 vs CON; 0.62±0.03 mm, P>0.05) or FMD (ATH; 3.6±0.8 vs CON; 5.6±1.2 %, P>0.05) was observed. Furthermore, there was no group difference in calculated CVD risk (ATH; 2.4 ± 0.6 vs CON; 1.6 ± 0.3 %, P>0.05). CONCLUSION: Middle-aged ATH with 10+ years of training for ultra-endurance races are not at a greater risk of developing CVD than individuals that are meeting current physical activity guidelines. 608 Copyright © 2019 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.