Clinically Relevant Altered Cardiac Function and Minimal Cardiac Damage during Prolonged Exercise

study was to examine markers of cardiac function and cardiac damage during a simulated half-ironman triathlon in highly trained athletes. Methods: Nine highly trained male triathletes volunteered for the study (mean SD; age: 33 3 yr; height: 1.8 0.1 m; body mass: 77.7 3.2 kg). The subjects completed a half-ironman triathlon; 1.9-km swim in an indoor 20-m pool, followed by a laboratory-based 90-km cycle and 21.1-km run. Venous blood samples were drawn and echocardiographic assessment completed before the start of exercise, immediately after each stage, and 24 h postexercise. Serum was analyzed for total creatine kinase activity (CK), creatine kinase isoenzyme MBmass (CK-MBmass), and cardiac troponin T (cTnT). Left ventricular systolic (stroke volume, and systolic blood pressure/end systolic volume ratio (SBP/ESV)) and diastolic (ratio of early [E] to late [A], ventricular filling E:A) measurements were derived from echocardiographic assessment. Results: The mean completion time of the half-ironman triathlon was 301 28 min. Left ventricular contractility (SBP/ESV) was significantly reduced after the half-ironman triathlon (P 0.05). A significant reduction in E:A was observed after the run phase of the half-ironman triathlon (P 0.05). Significant increases in CK and CK-MBmass were observed during and after the half-ironman triathlon (P 0.05), and cTnT was elevated in four subjects over the course of the half-ironman triathlon. Conclusions: The physiologic stress imposed by the half-ironman triathlon resulted in a reduced left ventricula